compact heart located dorsally and to the rear of the cephalothoracic part, is an elastic, muscular sac enclosed within a thin membrane. (pericardium). A small ... wall has three pairs of ostia; two on the dorsal, two on the ventral, and two ...... is not what the optimum protein composition for red swamp crayfish is. Lipids also ...
( A Fast Spreading Freshwater Invasive Crustacean)
Prof. Abdalla M. Ibrahim
Prof. Magdy T. Khalil
Faculty of Science, Ain Shams University, Egypt. Publication of Center of Researches & Studies of Protectorates, Ain Shams University, No. 1.
2009 1
Foreword Issues of invasive species have become prominent topics among the studies on biodiversity. These species of plants, animals and micro-organisms are transported by humans, advertently or inadvertently, to areas far beyond their natural geographical ranges. The new territories may provide particularly favourable habitat conditions, often away from natural enemies prevalent in their homeland; and these alien species become naturalised and may outperform indigenous species. Studies on biodiversity losses recognize "invasive species" as one of the causes of these losses. In the treatise embodied in this volume, the authors present the story of two crayfish species brought to Egypt (the River Nile) by a venture experiment of aquaculture. The experiment was eventually abandoned and the alien species were set free into the favourable habitat of the river and its network of canals. The two species had different fortunes; one flourished and the other succumbed. The main bulk of the book comprises six chapters amounting to a comprehensive treatment that may be summed as: auto-ecology of Procambarus clarkii as a naturalised alien species in the Egyptian Nile Basin. The other species P. zonangulus eventually disappeared after it was set free from the aquaculture farm. Chapter 1 describes in some detail the morphology and anatomy of the body and its organs. Chapter 2 deals with processes of growth and reproduction as performed in the "new home". These processes, especially processes of reproduction, are not replicas of processes in "native home" in North America; fecundity seems to fare better in the host habitat where it reproduces twice a year, and not once. 2
Chapters 3 and 4 deal with the eco-physiology of the crayfish, including responses and apparent adaptation to the new environment. These studies provide basic information that form guidelines for management of crayfish expanding populations. Chapters 5 and 6 address issues of uses of crayfish as a resource that provide materials for food, feed, fish-meal, etc. Information embodied in these two chapters provides elements for assessing the cost-benefit balance of introducing the species to wild fishing and future aquaculture enterprise. This is a monographic treatment of a case-study of an alien species that became naturalised in the River Nile (Egypt), with benign prospects and non-benign impacts on the river and its network of canals. The authors have admirably collated available information with their own data collected during several years of general ecological surveys and a set of detailed studies on two selected sites. Their syntheses present an integrated treatise on the subject, and set a most welcome example of a treatment that: (1) is based on a broad cover of scientific information, (2) provides evaluation of an alien naturalised species, and (3) sets elements for guidance to ventures that aspire to use crayfish species in aquaculture. It also provides guidance for studies on the innumerable alien plant and animal species that have become elements of the biota of Egypt. This is a commendable book that provides for needs of education, development and research.
M. Kassas University of Cairo
January 2009
3
Introduction and overview
A widespread practice among human inadvertently destructive activities is the introduction of "exotic" animals and plants into many areas of the world. Included in these transfers are various species of freshwater crayfish. There are over 400 species of freshwater crayfishes within the families Astacidae, Cambaridae and Parastacidae (Huner & Lindqvist, 1995). The crayfish of our concern is Procambarus clarkii (Cambaridae) which had been accidentally introduced to the Egyptian Nile water via a private fish farm during early 1980's (Ibrahim et al., 1995). This species is native and very common in many freshwater bodies of south-central U.S.A., especially Louisiana (Huner, 1995). It accounts for at least 80% of all wild and cultured crayfishes harvested around the world (Huner, 1989). Over 60,000 tons of P. clarkii are produced annually in the USA and China (Huner et al., 1993). On the other hand, the White River Crayfish Procambarus zonangulus, which is a closely related species to P. clarkii, was found in association with it in some localities along the River Nile. It is known to be also native to the south central United States (Hobbs et al., 1989; Huner, 1995). Both P. clarkii and P. zonangulus (Fig. 1) share common physiological traits that have made their wide distribution and commercial aquaculture more feasible than other crayfish species. Both have higher adaptability to burrow habitats, aerial exposure, rapid growth, high fecundity and disease resistance (Huner & Lindqvist, 1995). But after about one year survey, P. zonangulus disappeared completely from water bodies of Egypt; and this may be due to its preference to running water environment.
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The majority of introductions of these crayfishes have had negative consequences (Sommer and Goldman, 1983). In Egypt, most of fishermen complained that such crayfish harmed the fisheries productivity as it attacked the fish nests and consumed the eggs, while others claimed that it destroyed the irrigation system (Fig. 5), because of its burrowing behavior and tunnels made in banks of ditches and channels. Therefore, a thorough knowledge of its bionomics, biology, reproduction and distribution patterns in the new habitat seems very important. Therefore, several studies have been carried out to elucidate major features of the life cycle of both species, in addition to their mode of living, natural growth rates and their real updated distribution along the River Nile ecosystem. For catching the crayfish in Egypt, we found that the Egyptian illegal trap (Gobia, Fig. 9) was the most effective harvest method, while in USA they usually use the pyramid trap (Fig. 8), which has different numbers of entrance funnels at its base. The ecological surveys indicated that the crayfish has flourished and widely spread all over most of the River Nile and its tributaries and also in some of the newly inhabited areas in Egypt; reaching to some ditches in Sinai desert through the irrigation system. The range of the crayfish populations has clearly expanded northwards since the middle of 1980's until Damietta and Rashid and southward up to Aswan. Generally, they appeared relatively more abundant in Qalyoubiya, Cairo and Giza governorates than in El-Menoufiya and El-Sharkyia. In Giza governorate, crayfish were frequently reported in the main Nile and in Ibrahimia Canal. All water courses in this governorate near to Nahia, Warrak El-Arab, Abou-Rawash region, El-Zumur and El-Maryouteya canals were variably populated with the crayfish.
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Fig. 1. Difference between the red swamp crayfish Procambarus clarkii (a) and the white river crayfish P. zonangulus (b)
Fig. 2. Lateral view of a female crayfish Procambarus clarkii carrying eggs 6
Fig. 3. Cross section of crayfish burrow
Fig.4. Opening of a crayfish burrow. Fig.5. Damage of levees due to crayfish burrows
7
Fig. 6. Biomphalaria alexandrina shell remains after devouring by the Crayfish
Fig. 7. Cannibalism phenomenon in the Crayfish 8
Fig. 8. American pyramid trap for collecting crayfish
Fig. 9. Egyptian trap (Gobia) 9
The qualitative life history and the natural growth curve of Procambarus clarkii have been studied on two populations in two localities of the River Nile; one in Cairo governorate and the other in Qalyoubiya governorate (Ibrahim et al., 1997). Despite observed field variation, no significant difference was observed between growth rates of the two populations. Procambarus clarkii exhibited a clearly defined 2-year life span with two separate breeding stocks; one in mid spring (April) and the other in late autumn (November). The crayfish active season began in late March, when the temperature increased (22°C) and the water level in different channels and ditches raised (after the winter closure). The animals emerged from burrows (Figs. 3&4) moved to all parts of their habitats and began feeding on decomposing plant matter, snails and decayed fish. Egg-carrying females (Fig. 2) appear almost immediately after 2-weeks period of feeding, and become abundant throughout April. Newly hatched crayfish emerge in great numbers, on the back of their mothers during late April and early May. The young crayfish grow at a mean rate of 4.3 mm per week during summer, then decrease to only 2.9 mm per week during winter. The life history of P. clarkii in Egypt, appears little different from that described on the same crayfish from the southern United States (Huner and Barr, 1981). The USA population has only one generation per year and a breeding peak occurring in early summer. Growth rate is little lower than that of the Egyptian population, and this may be due to the relatively low temperature in USA during late autumn and winter, when the water temperature markedly decreases (16 °C); then the crayfish adults seem to retreat to burrows in banks of channels and ditches. Burrow analyses conducted in many localities have demonstrated that the animal has a strong capacity for survival under these conditions for a long time. Adult crayfish are able to live in burrows throughout late fall, winter and early spring. Furthermore, burrow excavations reveal that the tunnels may have no free water, or 10
water becomes nearly anoxic. Hasiotis (1993) provided an excellent descripiton of the surface morphology of burrows that promoted water retention. Moreover, Hobbs (1981) and Horwitz & Richardson (1986) classified crayfishes on the basis of their burrowing behaviour, where P. clarkii and P. zonongulus excavated relatively simple diagonal burrows, 1-2 m deep. Huner & Barr (1991) and Huner (1995) categorized them as tertiary burrowers. They retreat to burrows only when surface waters disappear, temperature decreases or to lay and incubate eggs. McMahon (2002) mentioned that the very low oxygen level in burrows (0~3 mg L1) was below that at which such species may successfully engage in continuous aquatic respiration. As a result, they must depend on atmospheric oxygen to meet their oxygen needs and do so very well indeed. McMahon (2002) showed that P. clarkii haemolymph oxygen affinity was two times that of a "water breathing" crayfish species. Moreover, when Hobbs (1975) and Huner & Lindqvist (1995) described adaptations that permitted crayfishes to live in barrows, they mentioned that their branchial chamber had become more vaulted and thus accommodated increased gill filaments-surfaces. This serves the crayfish well in use of atmospheric oxygen. In the Lab, Ibrahim et al. (1995) and Sleem & El-Hommossany (2008) studied the feeding behavior of P. clarkii and they indicated that it was a polytrophic animal, had a large feeding capacity to diverse food, even dead organisms. It consumes large number of snail species, hydrophytes and fish species commonly found in nature in Egypt. Regarding the freshwater snails, the crayfish tends to be selective when it comes to them as a food. This depends on the size of the snail and the hardness of the shell . The Lab experiments showed that the snails, Biomphalaria alexandrina, Physa acuta, Lymnaea natalensis and Bulinus truncatus are easier preys to be attacked by P. clarkii (Fig.6). This is primarily because the shell is thin and easy to break, so getting to the soft parts is not a problem. They usually crush the shell between their large claws and eat the soft body of the snail. It was noticed that one 11
crayfish could devour about ten of the large snails from the above four snail species during the first day of offering them to it. The field survey also showed high reduction and sometimes complete disappearance of these trematode vector snails in the irrigation channels, that had been invaded by P. clarkii, compared to water courses which did not harbor the crayfish, where high densities of these vector snails were recorded .So, these studies provide encouraging indication about the possible control of schistosomiasis and fascioliasis vector snails in Egypt by such crayfish. Finally, it is very important to use this exotic animal in a positive way instead of leaving its growing populations causing many problems to the freshwater ecosystem. The major obstacle to its common utilization (consumption) in Egypt may be due to non familiarity with its benefits as a cheap protein source compared to the marine shrimps. The following chapters attempt to present results of selected studies, which have been conducted during the last decade on the ecology, biology, and physiology of the crayfish P. clarkii, and we hope to continue these investigations in other practical and applied aspects to get the greatest benefits from this new natural resource in our aquatic ecosystem.
The authors
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Chapter 1 General Description 1.1. External Anatomy 1.1.1. The Body The characteristic body of the crayfish can be divided into three parts; the head and thorax without apparent segmentation and are combined into a cephalothorax, while the abdomen is clearly segmented. The entire length of the body is composed of 20 somites (six in the head, eight in the thorax, and six well defined in the abdomen). The somites of the cephalothorax are covered by a hard shield or carapace that encloses the back and sides. A cervical groove demarks the head from the thorax. The abdominal somites contain a transverse back or dorsal plate called a tergum. A lower or ventral sternum is joined to the tergum by the pleuron. The compound eyes are stalked and movable and are set in front of the carapace. The mouth opens on the anterioventral side of the head, between the mandibles. The anus opens ventrally before the telson at the end of the abdomen. On each side of the thorax is a large gill chamber covered by the free sides of the carapace. 1.1.2. Appendages Crayfish has a single pair of biramous jointed appendages attached to each somite. Although they function differently, yet have similar homologous parts. All have a protopodite, made up of two joints; the coxopodite and the basiopodite. The general pattern is to have two branches arising from the basipodite, which are the endopodite and the exopodite. This is the biramous (branching) condition. However, the exopedite is frequently reduced or missing. In case of the second and third maxillipeds (jaw legs) and the pereiopods (walking legs), the endopodite is composed of five segments. There are six groups of appendages. Each group functions according to its origin. The sensory appendages are made up of the antennae and the shorter antennules. These structures receive and 13
transmit the sensory stimuli of the environment. The mouth-parts consist of the chewing mandibles that crush the food and two other groups of appendages, the maxillae and maxillipeds, which handle the food. The large characteristic claw or pincer (chela) is used to grasp the food. The next four pairs of pereiopods are primarily used for walking on the ground; however, they handle food and act as cleaning hands for the body. The second and third pairs of maxillipeds and the five pairs of pereiopods have gills, attached to their protopodites. The pleopods, or swimmerets, are important for supporting and incubating the eggs. Their movement circulates the water in and around the eggs to promote respiration. The first two pairs of pleopods in the male are modified to transfer semen to the female. Semen is stored in the annulus ventralis of the female, located between the fourth and fifth pairs of pereiopods. Sexually active males also have prominent "hooks" on the third and fourth pairs of pereiopods. These assist in grasping the female during the mating act. The uropods are paddle-shaped appendages to the sixth abdominal somite. They, along with the telson, form a tail fan used for the characteristic backward swimming behavior of the crayfish. Regeneration of appendages The crayfish is very susceptible to mutilation either voluntarily or involuntarily. Mutilations can be self-inflicted such as when a limb is trapped in a crevice and simply discarded so that the animal can move away, or when it is seized by an enemy and abandoned to escape. Very often the animal is mutilated at the time of mating and it is quite frequent at the time of moult when an appendage can be left in the old exoskeleton. Whatever the cause the mutilation is followed by a regeneration in which the lost part is replaced. The replacement is never as good as the original. A small bud-like growth appears first of all. This grows fairly rapidly, followed by a period of inactivity, and then it again increases in size.
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A
B Fig. 10. External anatomy of the red swamp crayfish. (A. dorsal side; B. ventral side) (http:// crayfish.byu.edu/)
O
Fig. 11. Internal anatomy of the red swamp crayfish (www.infovisual.info)
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Fig. 12. Appendages of a crayfish 1. 2. 3. 4.
Antennule Antenna Mandible 1st Maxilla
5. 2nd Maxilla 6.1st Maxilliped 7. 2nd Maxilliped 8. 3rd Maxilliped
9. Cheliped 10. Pereiopod 11. Pleopod 12. Uropod
1.1.3. Exoskeleton The red crayfish exoskeleton is made up primarily of inorganic calcium carbonate (CaC03) in the form of calcite that is supported by an organic matrix formed of a compound called chitin and various protein molecules. The percentage of calcium carbonate remains fairly constant during the intermoult stage, regardless of age, but the thickness of the shell increases as the crayfish grows older. The exoskeleton of crayfish consists of four layers; an outer, uncalcified epicuticle, a calcified exocuticle, a calcified endocuticle, and an inner, uncalcified membranous layer. The dominant layer is the endocuticle, accounting for more than 80 percent of the total thickness. In order for growth to occur, the old exoskeleton must be periodically shed and a new exoskeleton promptly 16
synthesized. When moulting ceases temporarily at maturity, additional layers of endocuticle continue to be accumulated until the next premoult period begins, normally following the completion of reproductive activity.
Table .1. The segments and their related appendages with their functions Segment Appendage Functions 1 Preantennal. Two ocular peduncles Vision 2 Antennule Balance, touch, smell, taste 3 Antenna Touch, smell, taste Mandible Crushing food 4 1st Maxilla Filter feeding 5 2nd Maxilla Filter feeding 6 1st Maxilliped Respiratory, feeding, taste 7 2nd Maxilliped Respiratory, feeding, taste 8 3rd Maxilliped Respiratory, feeding, taste 9 Cheliped Fighting, holding (The large 10 Pereiopod (1 st Walking leg) claw) 11 Pereiopod (2nd Walking leg) Walking, holding (A small claw). 12 Walking, holding (A small claw). Pereiopod (3rd Walking leg) Genital opening of female 13 Pereiopod (4th Walking leg) Walking. No claw 14 st 1 Pleopod (Swimmeret) Walking. Genital opening of male 15 Circulation of water nd 2 Pleopod (Swimmeret) Seminal channel in male 16 Circulation of water Egg carrying in female rd 3 Pleopod (Swimmeret) 17 Seminal channel in male 18 4th Pleopod (Swimmeret) Circulation of water th 5 Pleopod (Swimmeret) Egg carrying in female 19 20 6th Uropod (Paddle) Egg carrying in female Backward swimming. Protection of eggs in female
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1.1.4. Physical Variations One unusual variation among crayfish is the occurrence of male secondary sexual characteristics in mature females. The presence of hooks on the walking legs and the development of the first pair of swimmerets to resemble the corresponding male swimmerets (gonopods) cause some females to look like males. Some have referred to such variations erroneously as hermaphroditism or the presence of both sexes in the same animal. They are really pseudo (false) hermaphrodites because such animals are invariably functional females; however, a case of true hermaphroditism has been observed in the red crayfish. It is not clear if these conditions are genetic or hormonal. Pseudohermaphrodites have seldom been seen. Literally hundreds of thousands of red crayfish have been examined by scientists and qualified laymen, but fewer than a dozen of the pseudohermaphrodites have been reported. This is unusual because the pseudohermaphroditic phenomenon is relatively common in other cambarid crayfish. Anyone examining large numbers of red crayfish will frequently find animals with disfigured bodies. This can take the form of a grotesque claw, an awkwardly bent carapace, or a broken carapace exposing the gills. These anomalies are the result of mechanical damage and subsequent regeneration of damaged or missing body parts. Another noticeable variation in red crayfish is the width of the palm of the claw. It may be spatulate (shovel shaped) or narrow (needle nosed); however, the spatulate shape is the most common situation. The palm of the claw of mature males is elongated when compared with that of mature females. 1.2. Internal Anatomy 1.2.1. Muscular System Crayfish muscles are all contained within the exoskeleton and are arranged in opposed pairs with a flexor muscle to draw the part of the body to a point of articulation (connection) and an extensor muscle to straighten the part. Since most muscles have at least one connection with the exoskeleton, a soft crayfish is at considerable disadvantage. 18
In the abdomen and above the intestine, there are two pairs of extensor muscles, which originate at the sides of the thorax and fill the upper part of the abdomen. The massive abdominal flexor muscles, which provide the driving power for the tail fan, are located below the intestine. They also originate in the thorax with connections throughout the abdomen ending at the telson. Other important muscles include those of the claws, the mandibles, the stomach, and the various limbs. All crayfish muscles are edible, but because of their relatively large size, normally only the claw and abdominal muscles are eaten. The meat removed from the abdomen is called "tail" meat by most laymen. This is technically incorrect since the telson and the uropods are the true tail of the crayfish. It should be called, more correctly, abdominal meat. 1.2.2. Respiratory System Crayfish obtain oxygen and eliminate carbon dioxide through gills. The gills contain blood sinuses and are located on both sides of the thorax in gill or branchial chambers. The branchial chamber is formed by the lateral sides of the carapace, and external to (outside) the body. A paddleshaped projection, called the scaphognathite, of the second maxilla beats back and forth below the mouth and draws water into the branchial chamber. The water circulates from beneath the pereiopods and from the rear of the chamber passing forward to the upper portion of the chamber and exiting below the mouth. In crayfish, there are two types of gills; the podobranches and the arthrobranches. The podobranches arise from the protopodites of the second and third maxillipeds and the first four pairs of pereiopods (one per appendage). The paired arthrobranches arise from the body wall adjacent to the second and third maxillipeds and the first four pairs of pereiopods. Thus the total number of gills is 34, 17 on each side. As long as a crayfish's branchial chamber is moist, it can obtain oxygen, which diffuses from the atmosphere into the water, where it is transferred to the gills and moves into the blood. The red crayfish can 19
survive for several weeks out of water as long as its branchial chamber is damp. This is one reason for its survival in the humid parts of burrows rather than in the water below, which is often very low in dissolved oxygen. This ability permits them to live in surface waters when oxygen depletion takes place because of the rapid decomposition of vegetation in the water. Crayfish can simply climb to the surface and raise one side of the carapace out of the water so that atmospheric oxygen can then enter the branchial chamber on that side. On the dorsal side, the red crayfish has a small furrow between the two halves of the carapace, which is referred to as the aerola. Anatomically, this means that there is a larger branchial chamber and more space for gill filaments. This increases the crayfish's ability to obtain oxygen from water. In general, crayfish from habitats with little or no problems with oxygen have wide aerolas, while those from oxygen-poor habitats generally have very narrow aerolas. 1.2.3. Digestive System The crayfish is a voracious and indiscriminate feeder. It is safe to assume that a full-grown crayfish will consume several times its own weight in the course of a year. Yet the increase of the animal's weight with respect to food intake indicates that a very large portion of the assimilated food is utilized for energy. The first step in the process of feeding is to separate the nutritive parts of the food matter from its indigestible parts. This preliminary operation is the subdivision of the food into a convenient size for ingestion into the digestive tract. Food may be seized by the pincers or by the anterior ambulatory appendages and transferred to the first or second cephalic appendages. These appendages grasp the food and thrust it between the mandibles. The latter crush and divide the food brought to them as it passes between their toothed edges at the opening of the mouth. The alimentary canal extends from the mouth at the anterior end to the anus at the posterior. A short oesophagus leads upward from the mouth into a large stomach. The stomach is divided into a large cardiac 20
chamber and a small pyloric chamber. In the cardiac chamber the food particles are ground and crushed by the gastric mill. The mill contains three chitinous teeth, which are controlled by muscles, which triturate the food as it moves into the stomach. A fibrous strainer permits only the smallest particles to pass into the stomach's pyloric chamber. The pouched midgut region contains glands that secrete enzymes and absorb food matter, while the major digestive gland is the hepatopancreas. This is a trilobed structure with two lobes projecting forward on either side of the stomach and the third lobe projecting to the rear of the carapace. The midgut is very short and not lined with chitin. Most of the digested food passes into the hepatopancreas through tubes from the midgut and is absorbed there. The hindgut (proctodeum) extends from midgut and ends with the anus below the telson. Gastroliths are the so-called "stomach stones." These are calcium carbonate stones found on either side of the cardiac stomach. As the moult approaches, some of the calcium carbonate extracted from the old exoskeleton is stored in the gastroliths. During moulting, the joined lining of the oesophagus and stomach, including the gastric mill, passes forward through the mouth. The gastroliths come to lie in the cavity of the stomach, where they are dissolved. The body absorbs the calcium carbonate from the gastroliths for the initial hardening of the exoskeleton and mouth parts. There is enough calcium carbonate in the gastroliths, hepatopancreas, and blood to harden the new exoskeleton to about onethird the normal level. 1.2.4. Circulatory System Circulation in crayfish is similar to that in most other arthropods in which an open system consists of a heart, arteries, and sinus cavities. The compact heart located dorsally and to the rear of the cephalothoracic part, is an elastic, muscular sac enclosed within a thin membrane (pericardium). A small space between the heart and the membrane is called the pericardial sinus. Hemolymph (blood) enters from the pericardial sinus through three pairs of openings called ostia. The heart 21
wall has three pairs of ostia; two on the dorsal, two on the ventral, and two on the lateral sides of the heart. Valves are located in each of the ostia to prevent the outflow of hemolymph . Hemolymph is pumped to the head through a single artery (median ophthalmic artery). After passing above the stomach, the hemolymph flows into a pair of arteries that supply the optic region. It is pumped to the abdominal region by the dorsal abdominal artery, which runs above the intestine. This artery forms many small branchings that supply hemolymph to the dorsal muscles of the abdomen. At its origin near the heart, the dorsal abdominal artery divides into a second branch, the ventral abdominal artery. This artery further divides into two additional branches that pass through the thoracic canal. These arteries carry hemolymph to the anterior and abdominal regions. Several other arteries supply the antennae, the green glands, the digestive gland and reproductive system. Once hemolymph reaches the various body regions and tissues, it enters open sinuses, where it bathes those tissues in these open areas, and an exchange of food, waste products, oxygen and carbon dioxide takes place. The hemolymph then returns to the heart by gradually flowing through and around body organs. No veins are involved. This is why the crayfish's circulatory system is said to be open. This open system circulates oxygenated blood to many organs of the crayfish. The gills resupply the deoxygenated hemolymph with oxygen. From the gills it circulates to the heart and is pumped throughout the body. Oxygen diffuses into the hemolymph largely through the gills. Cells do not carry the oxygen. Rather, it is carried within the hemolymph, normally combined with hemocyanin. Hemocyanin (similar to hemoglobin in vertebrate animals) contains a copper porphyrin molecule that responds to oxygen as does the iron in hemoglobin by binding the free oxygen from the water. One major reason a crayfish is able to live at relatively low oxygen levels is the ability of copper to bind the oxygen. One gram of copper in crayfish blood can fix more than 176 cubic centimeters of oxygen. This is more than ten times greater than the
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binding ability of iron in mammals. Oxygenated hemocyanin has a faint blue color so that crayfish may be said to be "blue blooded." 1.2.5. Reproductive System Crayfish are dioecious, that is the sexes are separate. Both males and females have trilobed gonads. Two of the three male or female gonad lobes run anteriorly, below the heart and above the intestine. In females, two tubes, or oviducts (one from each side of the ovary), pass to openings in the genital papillae located at the base of the third pair of walking legs. Before and after egg laying, the openings are covered by a very thin layer of exoskeleton. In males, two tubes, the vas deferens (one from each side of the testes), pass to openings in the phalic papillae at the bases of the fifth pair of walking legs. As in females, these openings are covered by a thin layer of exoskeleton. Sperm is transferred from the male to the female by way of the first pair of pleopods on the male. The second pair of pleopods also assists in the transfer. Both pairs are called gonopods. The sperm is stored in a structure located between the legs of the female called the annulus ventralis, or seminal receptacle. The sexually mature crayfish, male or female, assumes distinctive secondary sexual characteristics. The male exhibits the most dramatic change in body proportions. The claws become elongated and greatly enlarged. Distinct hooks appear at the bases of the third and fourth pairs of walking legs, and the first two pairs of swimmerets (called gonopods), located between the walking legs, become cornified (hardened). These serve to transfer sperm to the female. The large claws and hooks serve to grasp the female while mating. Physical changes in the female are not as apparent, although the claws enlarge to a degree. In red crayfish a conspicuous gap forms between the fixed and movable fingers of the claws so that the male can grip the claws of a female during mating. The annulus ventralis also cornifies and a very distinct groove forms when the female moults to the sexually active phase. The presence of hooks on the males is unique to crayfish of the family 23
Cambaridae. Males that have distinct hooks, cornified gonopods, and enlarged claws are called Form I males. Following production of young, a unique metamorphosis takes place in both the male and female crayfish. They begin to eat voraciously and within two to three weeks, moult. When they complete this moult, they again assume the juvenile appearance. This is referred to as Form II state for males. The Form II condition arises after a male or female has reached sexual maturity (Form I) and moulted to the sexually inactive state. Thus, any male that has not matured is properly described as a juvenile. Distinction between juvenile and Form II males is not easy. Initially, there is a distinct gap between the bases of the first pair of swimmerets, or gonopodia of juvenile males; but this gap narrows as the male goes through successive moults, to the point that just before the Form I moult, the gap is very narrow. As a result, a narrow gap between the swimmerets is indicative of either a juvenile male about to moult to the Form I state or a true Form II male. 1.2.6. Excretory System The green glands are the major structures involved in the production of urine. Each green gland is made up of five major parts. This remarkable organ consists of an end sac surrounded by hemolymph and connected to a labyrinth (excretory tube) leading to a bladder. The exit duct of each gland leads to openings (excretory pores) located on the inner side of the basal segments of the antennae. That is why green glands are also referred to as antennal glands. Wastes are removed from the blood by changes in the hydrostatic pressure in the end sac. On the other hand, P. clarkii have water constantly flowing into their bodies because the concentration of dissolved substances, organic molecules, and inorganic minerals (salts), is much higher in body fluids than in the water surrounding them. This movement of water is a special kind of diffusion called osmosis because the water is diffusing through semipermeable body membranes. The flow of water increases the osmotic pressure inside the body. Most of the crayfish's body is covered 24
with impermeable, heavily calcified shell, and this adaptation reduces the amount of osmosis; however, the branchial chamber, including the gills, is semipermeable and permits osmosis to occur. Excess water is eliminated largely by the green glands. The green glands produce large amounts of urine that are very low in dissolved salts and other solids. One investigator found that the adult P. clarkii normally produces a volume of urine equals to about 4.5 percent of its body weight in 24 hours. Naturally, when a crayfish is outside of water, whether resting in a humid burrow or crawling about on dry land, it is not absorbing much, if any water; therefore, very little urine is produced. This conserves water within the body. Crayfish can be considered as euryhaline because they can live in waters with quite varied salinities, from fresh water (with less than 0.5 parts per thousand (P) to brackish water (salinity up to 20 P). The preferred salinities, in which reproduction occurs, range from 0.0 to 4-5 P, while growth will continue at salinities up to 12 P. Salts, including the critically important calcium salts (integral part of the exoskeleton), are absorbed either through the digestive tract from food or by special cells in the gills that absorb them against a concentration gradient. In fresh water, the concentration of dissolved salts is much lower than that in the hemolymph that the natural tendency is for those permeable salt ions to constantly diffuse out of the body. In P. clarkii, the levels of salts and water in the hemolymph and body tissues are controlled by hormones produced by neurosecretory centers in the "brain" and eyestalks. Eyestalk hormones are stored and released by the sinus glands. 1.2.7. Nervous System As in all arthropods, the nervous system of the crayfish consists of a central bundle of nerves with many single branching neurons (the central nervous system) and many smaller nerve bundles branching throughout the body (the peripheral nervous system). Concentrations of neuron cell bodies called ganglia form coordination centers. These major 25
nerve bundles run along the ventral side of the body. Each body segment contains a paired ganglion. Those of the first three segments fuse above the oesophagus. This fused mass referred to as the supraoesophageal ganglion, found at the anterior or front end of the nerve cord is larger than the other ganglia, and is often considered as the brain. The crayfish brain is given names to the three pairs of fused ganglia. The anterior part is called the protocerebrum, the mid-part is called the deuterocerebrum, and the hindmost is called the tritocerebrum. Small nerves branch from the brain and innervate the optic (eye) region, the antennules, and the antennae. A pair of neural bands, the circumoesophageal connectives, pass backward from the brain around the oesophagus, and join a large ganglion, the suboesophageal ganglion below the oesophagus. Branches from this huge composite ganglion innervate the mouth appendages, the green glands the oesophagus and various muscles in the anterior region. A large ventral nerve cord originates from the suboesophageal ganglion and passes through the abdomen. Fused segmental ganglia in each segment are found in pairs along the ventral nerve cord that send fibers to the appendages, muscles, and near organs. The various ganglia of the brain and ventral nerve cord of the nervous system are called the central nervous system. The peripheral nervous system consists of all nerves connecting to the central nervous system. It has two subdivisions, the voluntary nervous system and the involuntary, or sympathetic nervous system. The voluntary nervous system controls voluntary movements of various limbs and the abdominal muscles through the ganglia of the "brain" and the ventral nerve cord. The sympathetic nervous system regulates involuntary body functions such as heart beat, digestive gland function, stomach movements, and similar processes. That is, it controls systems that must continue to function at all times. The sympathetic nervous system arises from ganglia in the circumoesophageal connectives (one in each side). 26
Sensory Receptors Crayfish have one of the most advanced sensory systems of all the crustaceans. They have well developed sensory receptors for vision, chemicals (chemoreceptors), balance, touch (tactile receptors), and internal muscle tension (proprioceptors). On land, the crayfish is slow and clumsy so it must be able to rapidly detect enemies. It does so with excellent vision (including color) and tactile receptors. In the aquatic environment, the eyes are used so long as the water is relatively clear, yet the turbid water reduces the efficiency of the eyes. Crayfish also receive appropriate information from chemoreceptors, which detect food, potential enemies, and other crayfish, and from tactile receptors, which detect vibrations and water movements. The compound eyes of crayfish are similar to those found in large shrimps. They are covered by a transparent membrane called the cornea. The compound eye is composed of many smaller units or facets called ommatidia; as many as 2,500 ommatidia make up one eye. Each ommatidium is composed of several different cells that serve to collect light from objects and translate the information to the brain.
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Chapter 2 Growth and Reproduction 2.1 Growth and moulting process Growth in crustaceans like all arthropods is discontinuous due to their rigid cover known as the exoskeleton .Therefore, in order to grow in size; the crayfish must get rid of such cover by moulting or ecdysis. The exoskeleton is made up of chitin structure formed of a polysaccharide, chemically termed as acetyl glucosamine (C32 H54 O21 N4). The crayfish exoskeleton is particularly massive compared with shrimps of comparable size; that can be particularly seen in the large claws and the stout carapace and may be an adaptation to its benthic life. In preparation for moulting, crayfish cease to feed and their activity decrease. Initially, the lower layers of the exoskeleton are dissolved, withdrawing enough calcium to increase flexibility and thin the exoskeleton (Reynolds, 2002). Between 10% and 20% of the calcium required to harden the new exoskeleton is mobilized and stored in the gastroliths (Taugbol et al., 1997). After the exoskeleton is shed, the gastroliths drop into the crayfish's foregut, where they are gradually broken down to allow the absorption of the calcium. This calcium is used to re-calcify the mouth parts, enabling resumption of feeding. Stein (1977) reported that rapid hardening of the exoskeleton is key to limiting vulnerability to cannibalism. Ionic calcium in water aids in the hardening of the exoskeleton (Mally, 1980). During moulting process, the carapace splits dorsally and the animal rocks so as to detach itself from its outer layers of the exoskeleton and then extracts itself through the dorsal split (Fig.13). A complete moult involves shedding the cuticle from all exoskeletal parts, from the surface of the eyes and other sense organs to the ectodermal lining of the fore-and hind guts. As the foregut lining is shed, the gastroliths drop into the lumen of the for-gut, where they are gradually broken down and their contents mostly resorbed by ________________________________________ Madleen M. Habashy 28
the gut epithelium and the hepatopancreas (Reynolds, 2002). Calcium thus resorbed is transferred to the cuticular epithelium by way of the haemolymph. Remineralisation is affectively almost complete within 2 to 4 days, although it probably continues very slowly throughout the intermoult (Taugbol et al.,1997). Tero Ahvenharju (2007) reproted that during hormonal regulated complex process (moulting), the multilayered rigid exoskeleton is shed and the new soft integument comes out from underneath it. The new cuticle is soft and pliable allowing growth to occur, then it soon hardens preventing further growth in size till the next moult. However, growth in weight continues to take place as long as the animal is feeding and thus accumulating more tissues in its body. Some factors affect the moulting process; among these factors eyestalk ablation. It is the most effective and induces moulting by directly affecting the endocrine system of the crayfish (Change, 1989; Huner, 1995). In this respect, Ibrahim et al. (2000) reported that the bilateral removal of eyestalks has induced precocious moult and accelerated the growth of juvenile crayfish. Removal of three pairs of walking legs or a pair of uropods has induced precocious moult without any effect on growth of the body. The average time required for 50% of the individuals to reach the fifth moult after the initial one was 38 days for eyestalksless crayfish, 97 days for legless and 134 days for uropodless crayfish, while the untreated crayfish required 161 days to attain the fifth moult. Moreover, the study revealed that as the temperature changed from 18 to 30 ºC, the mean time to moult interval for untreated animals was decreased from 63.2 to 21.4 days for mature and from 26.6 to 11.6 days for immature crayfish, while for eyestalkless crayfish it decreased from 12.8 to 5.9 days for immature and from 20.9 to 7.9 days for mature crayfish.
2.1.1 The integument structure The exoskeleton in most decapods is relatively thickened and robust, and formed from several layers. The epidermis or hypodermis (the basal, living layer), which secretes the inert cuticle, is a cuboidal epithelium underlain by a basement membrane, which forms the outer 29
boundary of the fluid-filled body cavity or haemocoel. Just below the epidermis are multi-celled tegumental glands, with ducts to the exterior (Fig. 14). The inner layers (endocuticle) consist of alternating layers of protein and chitin making it tough like plywood and yet flexible, at the joints. Next to the hypodermis is an uncalcified membranous layer overlain by a calcified endocuticle. A thin layer comes next, the exocuticle which is often pigmented; it is absent from the thin arthrodial membranes of the joints. Finally, the epicuticle has a proteinaceous cuticulin layer underlying a waxy layer with a surface "cement" layer. Crustacean exoskeletons have relatively little lipid compared to insects, but a degree of waterproofing is provided by cuticular thickness and by the quinine tanning of the lipoproteins (Reynolds, 2002).
2.1.2 Environmental factors affecting growth rate The growth rate of P. clarkii depends on several factors, including temperature, photoperiod, water quality (mainly dissolved oxygen, calcium and pH), shelter, nutrient levels and habitat composition (Aiken & Waddy, 1992). Moreover, some biotic factors, such as nutrition, production, density, sex, age, and maturity status have an effect on crayfish growth rate. In addition, the behavior, such as interspecific competition for food, habitat selection, movement and aggressive interaction with conspecifics may influence growth (Gherardi & Cioni, 2004).
2.1.2.1 Abiotic factors 2.1.2.1.1 Effect of temperature Water temperature is a major limiting factor for poikilothermic aquatic organisms (Firkins & Holdich, 1993; Verhoef & Austin, 1999). Temperature influences metabolic activity, food intake, survival and growth. Growth rate increases with increasing water temperature until the optimum is reached, and then declines with further temperature increase, following a bell- shaped curve. Hartnoll (1983) mentioned temperature and food supply as factors influencing intermoult duration. This has clear implications on crayfish farming. 30
Fig.13. Juvenile crayfish frequently moult, showing the dorsal split between the cephalothorax and abdomen
Fig. 14. Diagram of a vertical section of the crayfish integument (Lowery, 1988).
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Crustacean growth takes place only above a certain temperature, and is shown to increase with temperature up to a species- specific optimum. Below the minimum temperature for growth, crayfish are often sluggish and slow to feed. Around the optimum, the influence of temperature is less strong than that of other factors. Highly variable temperature or values above the optimum, may lead to delays in moulting and to increased mortalities following the moult (Jussila & Evans, 1996). Few studies were conducted on the effect of temperature on the growth rate of Procambarus clarkii in Egypt. Habashy (2004 a) studied the growth rate of P. clarkii at different temperature levels (15, 20, 25 and 30 ºC) under laboratory conditions, and found significant differences (P50mm carapace length) can produce over 600 viable young. However, Huner (2002) reported that ovarian eggs counts vary from around 50 in females of 60 mm total length, to 300 in 90 mm total length females, to over 600 eggs in 120 mm total length females. Under laboratory conditions, the maximum life span is about 4 years but it rarely exceeds 12-18 months in nature. Ando & Makioka (1998) concluded that the ovary of P. clarkii has a maximum length of 4 mm and a width of 5 mm and is composed of two anterior and one posterior sacs. Gherardi (2002) reported that cambarid eggs vary from 1.0 to 3.0 mm in diameter, averaging around 2.5 mm. In other species such as the Japanese crayfish (Cambaroides japonicus), Nakata & Goshima (2004) stated that both egg diameter and weight significantly increased with female body size, but were variable even for the same size crayfish. The Egyptian study conducted on P. clarkii, showed that egg laying starts in about late September or early October, when the peak of spawning activity is attained, but it may extend as far as April. The female lays eggs only once throughout the year, and generally, about 300 eggs are extruded by a female, with a range of 100 to 700 eggs. Moreover, results revealed that the number of eggs deposited is directly proportional to the size of the mother. Once eggs are laid, the female spends several hours turning from side to side, and during this movement, fertilization and 51
firm attachment of eggs to the pleopods is maintained. The fertilized eggs are black and nearly 1.6 mm in diameter (Soliman et al., 1998b). Other Egyptian study revealed that the number of ovarian eggs produced by female crayfish was directly proportional to the body size (r=0.98) (Fig. 22 ), and the minimum average number (168 eggs) was produced from females with 3.2 cm mean carapace length, while the maximum number (618 eggs) from female with 5.2 cm mean carapace length. Average number of ovarian eggs and that of young for different sizes of females is highly correlated (r=0.93). The incubation period of fertilized eggs ranged from 14 to 16 days (Mubarak, 2001). Also, the study cleared that the attached young per female increased with the increase of female carapace length (r=0.97) (Fig. 23).
2.2.9 Effect of environmental factors on reproduction Most research done has addressed a combination of two or more environmental conditions that affect crayfish reproduction (GutierrezYurrita, 2000; Storer et al., 2002). These include temperature combined with photoperiod (Portelance & Dube, 1995; Provenzano & Handwerker, 1995; Matsuda et al., 2002); photoperiod, substrate and shelter (Mason, 1979; Rouse & Yeh, 1995); density and sex ratio (Yeh & rouse, 1995; Verhoef & Austin, 1999). Egg laying and spawning of crayfish have been found to be influenced by the photoperiod, Dendy (1978) studied the effect of decreasing photoperiod on P. clarkii, and found that hours of light were decreased regularly beginning at the spring. Spawning occurred after about 100 days, when only 2 to 3 hr of light were provided each day. Provenzano & Hanwerker (1995) found that constant darkness produced the highest percentage of ovigerous females, while constant light produced the lowest percentage. The shortest mean time to egg laying occurred in constant short photoperiod and the longest mean to egg laying occurred in treatment of ambient and constant long days, but the differences were not statistically significant.
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Mean number of ovarian eggs – Linear (Mean number of ovarian eggs)
Carapace length (cm)
Fig. 22. Relationship between carapace length and mean number of ovarian eggs ( Mubarak, 2001 ).
Mean number of attached young – Linear (number of attached
Carapace length
Fig. 23. Relationship between carapace length and mean number ( Mubarak, 2001 ). 53
of attached young
In Egypt, Ibrahim et al. (2006) found that both temperature and photoperiod have an effect on egg laying in P. clarkii. Temperature of 30 ºC and above caused high mortality; lower percentage of ovigerous females and increased the required time to egg laying, while that of 27ºC gave the shortest time for egg laying, and the highest percentage of ovigerous female (36.6%) was observed at 29ºC. Meanwhile, the highest percentage of ovigerous females was obtained under complete darkness, while continuous light produced the lowest one. The shortest mean time to egg laying was produced with short photoperiod (6 hr L – 18 hr D), while the longest one was obtained with long photoperiod (18 hr L – 6 hr D). The effect of reduced water level on reproduction and survival of P. clarkii was studied by LaCaze (1970) who reported that the crayfish burrow during dry periods, where there is a little or no water above the ground and that they produce young in the burrows. This behavior which presumably led to the conclusion that lowering of water level in managed crayfish ponds is a necessary condition for reproductive success (Nelson & Dendy, 1978). Moreover, heavy metals affect egg production of female crayfish, since it was found that the mean number of eggs produced in control group (non treated crayfish) was 211 eggs and that produced after Cd and Pb treatments was 47 and 179 eggs, respectively. Both heavy metals caused a sharp decline in egg production as well as in their hatching (Mubarak, 2001).
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Chapter 3 Physiological aspects Since the introduction of the red swamp crayfish Procambarus clarkii in 1980s to Egypt, it has been rapidly expanding in all aquatic freshwater bodies including the River Nile and its tributaries, in addition to streams, ponds, irrigation canals, drains and marshes with polluted or natural waters. It became successfully adapted to the new habitats and so considered to be an important component of the present freshwater fauna. The biological processes, i.e. growth, life cycle and physiology of crayfish are relatively well known for European, American and Australian species (Huner et al., 1992; Correia 1995), but little is known about their habitats in Egypt (Ibrahim et al., 1995). This chapter focuses on the physiological adaptation of the freshwater crayfish introduced to the Egyptian environment .All organisms are adapted to their natural habitats and additionally, have the ability to acclimate to the changes that occur in such habitats. The process of acclimation involves physiological, biochemical, behavioral and other responses that allow the animal to compensate for changes that occur in the natural habitat. These changes vary from the very short- term to long-term developmental processes extending over much of an animal’s lifetime. The red swamp crayfish live in extremely variable habitats, which vary largely in levels of respiratory gases, excretory products such as ammonia, ionic composition, temperature and pressure. Additionally, many crayfish are able to tolerate a period of drought that may extend for several months, during which they burrows within which they can avoid a degree of environmental perturbation (Hobbs, 1975). _____________________________________________ Nahed Shafik Gad 55
3.1 Reception and transduction of environmental signals Crayfish are literally covered with sensors (exterioreceptors) that can perceive any environmental change. Each sensor is a receptor cell or a group of cells specialized to respond to changes in a particular environmental parameter i.e. mechanical, chemical, electrical or thermal changes. A receptor cell has three main functions: reception, transduction and signal treatment. Reception occurs as the environmental signal is received by receptors located at the exposed surface of the cells. Receptor cells are usually sensitive to only one moiety of stimulation and may be exquisitely sensitive, often responding to minute changes .Others have receptor molecules on the surface, whose conformational state is changed by environmental stimulus. A good example of these is found in the compound eye of the crayfish, where the photoreceptor molecule rhodopsin reacts with photons, causing a conformational shift in the molecule, altering its activation energy and allowing it to initiate a complex chain of chemical events in the cell membrane. This eventually causes changes in one or more membrane ion channels, which their opening or closing lead to electrical changes in the membrane of the receptor cells. Such changes are the end result of all environmental receptions and provide the mechanism by which the environmental change is transformed ( transduction) into one or more electrical events (e.g. action potential ) that can be communicated from cell to cell and through out the body. Signal treatment involves a variety of other functions that may be associated with the receptor cell. Such cells may, for instance, act to amplify the signal, focus the signal and encode the signal into a pattern which describes the form and intensity of the stimulus in terms of the central nervous system. Nerve cells are specialized to conduct such impulses to and from the central nervous system (McMahon, 2002).
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3.2 Physiological compensation Response to environmental changes may be direct and immediate as in the violent abdominal flexion that allows a crayfish to escape from a dangerous stimulus, or may involve compensatory responses. Two broad patterns of response are: conformation and regulation. In an animal conforming to an environmental change, internal levels are allowed to vary in concert with the environmental perturbation, while an animal that regulates maintains internal levels despite the environmental perturbation. An illustration of this difference is provided in Figure 24, when two crustaceans are exposed to declining environmental oxygen levels; animal A, an oxygen conformer, fails to respond to the situation and allows its oxygen consumption to fall proportional with the environmental levels, while animal B, an oxygen regulator, modifies oxygen uptake so as to regulate oxygen consumption at a constant level over a range of environmental levels.
3.3 Physiology of gas exchange Many of the physiological reactions involved in environmental compensation occur at the gill surface of crayfish, these are:
3.3.1 Ventilation Ventilation of the gills in the crayfish as in other decapod crustaceans, results from waving of the scaphognathites, (the paddle shaped exopodites of the second maxillae), which lead to a narrow current leading from each branchial chamber to the exterior via a pair of apertures lying on either side of the mouth. The crayfish ventilatory pump works efficiently to draw water through branchial chambers and across the gills (Burggren & McMahon, 1983).
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Fig. 24. Oxygen uptake plotted against ambient oxygen depletion , showing results for crayfish oxygen conformer(A) , where oxygen consumption decreases linearly with decline in external oxygen and crayfish oxygen regulator (B). ( McMahon & Wilkens , 1975)
3.3.2 Oxygen uptake Oxygen uptake across the gills is mediated by the gradient between venous haemolymph and inhalant ambient water and facilitated by the multi-capillary exchange system and by the rapid binding of the oxygen carrier molecule haemocyanin. The latter facilitates oxygen uptake by maintaining a large gradient for oxygen diffusion across the gills.
3.3.3 Oxygen transport Haemocyanin, the oxygen carrier of most arthropods, including decapod crustaceans, is a large polymeric protein carried in free solution in the haemolymph. Each molecule is an aggregate of several subunits. Each subunit contains an oxygen binding site and can have individual oxygen binding properties. Crayfish haemocyanin is either hexameric (6 subunits) or dodecameric (12 subunits) .As in all haemocyanins, oxygen binds between a copper molecule and several histidines that together form the binding pocket. 58
The binding forces are very weak and strongly influenced by small charges in the conformation state of the molecule. Oxygen uptake at the gills and release to the tissues, thus occurs quickly and efficiently in response to small changes in the molecular environment.
3.3.4 Carbon dioxide elimination Carbon dioxide produced from tissue respiration is removed by the blood vascular system and eliminated at the gills.
3.3.5 Vascular transport In crayfish, as in all arthropods, the blood vascular system is open, i.e at some point the haemolymph bathes the tissues directly .The vascular fluid (haemolymph) is propelled by a single muscular ventricle that is suspended inside a collecting chamber, the pericardial cavity. On contraction (systole), the heart pumps haemolymph into series of complex arterial distribution systems that supply broad regions of the body. Each arterial vessel breaks down into minute channels in the tissues, from whence haemolymph is collected by small sinusoids, which eventually coalesce into the major collecting sinus, the infrabranchial sinus, which delivers the haemolymph to the gills, through which it circulates before returning via the branchio-pericardial veins, to the pericardial cavity. Haemolymph entry into the ventricle occurs during diastole (relaxation). In each systole, some contractile energy is stored in stretching the elastic alary ligaments by which the ventricle is suspended. This energy is available in diastole to return the heart to its original volume.
3.3.6 Ionic and osmotic regulation All crayfish are found in fresh or brackish water (Holdich et al., 1997). Since ionic levels in fresh water are very low, all crayfish living in fresh water must strongly regulate both their osmotic and ionic levels. Several factors are involved in either limiting or compensating for the ionic and osmotic problems of life in the fresh water. Firstly, crayfish 59
are covered by a strong chitinous calcified exoskeleton that limits both water gain and salt loss across most of the body surface. In areas where the chitin is thin, such as the gills, permeability is still relatively low, due to modifications of the branchial epithelial cells. As a result, permeability of crayfish integument to water and sodium is approximately 1/100 that of a similar sized marine macruran. (Krischner, 1990). Even with this extremely low permeability, some water gain and ion loss occur and compensatory mechanisms are involved. Ion loss is corrected by active ion uptake across permeable surfaces. Since water enters the crayfish continually via osmosis, crayfish have no need to drink. Excess water is removed by the renal organs. Ion loss from the urine is prevented by ion re-uptake. In adult crayfish, the alimentary canal and gills are potential sites for uptake of new ions. Ion uptake across the alimentary canal occurs as a natural consequence of feeding, while ions, especially sodium and chloride, are known to be involved as cofactors in the uptake of many nutrients (Wright & Ahearn, 1997). Calcium and copper are known to be taken up across the midgut and this area also plays an important role in the detoxification of heavy metals ions (Dall & Moriaty, 1983).
3.3.6.1 Renal function Ion uptake occurs in the antennal glands (renal system) in crayfish. Potential urine enters the antennal organ largely via ultra filtration through the walls of the coelomosac, although an unknown proportion passes by various secretory processes ( Riegel, 1972) . Pressure for ultrafiltration is supplied by branches of the antennary artery (Kirschner & Wagner, 1965). Ultrastructural studies revealed that the epithelium of this region is composed of podocytes, cells which form pores that allow fluid to pass through the epithelium into the lumen to form the potential urine. Fluid passing through the coelomosac wall also passes through to basement membrane of the epithelial cells. This structure is composed of collagen and other fibrous material that create a molecular sieve through which only molecules of less than 2000060000 Da can pass. Thus, water, ions, nitrogenous wastes and other low 60
molecular weight substances are forced through the membrane into the urine, while cells and large molecules such as the protein dodecamer haemocyanin are prevented from leaving. The hydrostatic pressure difference is relatively small (2cm H2O) but this is sufficient to create a flow (filtration rate) of approximately 3 ml min-1. Only approximately 40% (1.3 ml min -1) of this passes out of the body as urine, indicating that modification of the constituents must occur in the antennal gland lumen. Control of Ca++ and Mg++ occurs at the level of renal tubule. Glucose reabsorption had also been reported for crayfish proximal tubule and amino acid reabsorption in crayfish bladder, all necessary ions, nutrients and other substances are reabsorbed in the renal tubules, leaving only water and waste water products .The antennal gland has also been implicated in acid- base balance and in detoxification of xenobiotics (Wheatly & Toop, 1989).
3.3.7 Mechanism of compensation to environmental variation 3.3.7.1 Oxygen depletion (Hypoxia). Fresh waters are notoriously variable, and this is especially true for oxygen levels, In fast flowing streams, oxygen levels may remain relatively high, but in static or slow moving waters i.e. ponds and lakes, oxygen levels may range from supersaturated to virtually anoxic seasonally and even diurnally. Supersaturation results during sunlight days, when oxygen is produced by floral photosynthesis, while extreme oxygen depletion (hypoxia) may occur at night, when all organisms are depleting the oxygen by respiration. Consequently, crayfish living in these more stagnant waters must clearly be exposed to severe hypoxia for periods of several hours on a daily basis. In consequence, crayfish generally tolerate at least short term hypoxia very well. Studies on the measurement of oxygen consumption in the crayfish Procambarus clarkii exposed to low ambient oxygen by Maynard (1960) suggested that this crustacean allowed ventilation and oxygen uptake to decline linearly with declining oxygen tension, i.e. where oxygen conformers are unable to regulate ventilation, gas 61
transport for oxygen consumption occurs at low ambient O2 levels. The crayfish responds to hypoxic exposure by an increase in both the rate and the stroke volume of the scaphognathite (ventilation) pump and a marked increase in ventilation volume. Subsequent studies showed that this crayfish was well able to maintain or even increase oxygen consumption when exposed to severe oxygen depletion (Burggren & McMahon, 1983).
3.3.7.2 Compensation for variation in temperature Rutledge (1981) showed that both standard metabolic rate and the scope for activity (active and standard metabolic rate) of the crayfish increase with raising the temperature from 10 0C to 20 0C. Oxygen levels and oxygen binding characteristics in crayfish haemolymph also vary with temperature. In crayfish tested at temperatures outside their acclimated range, haemplymph pH and the affinity of haemocyanin oxygen binding varied widely with temperature. Crayfish acclimated to 10, 20 or 25 0C, when tested at their acclimation temperature and under pH and other conditions appropriate for their haemlymph at that temperature, however, showed very similar oxygen affinity, suggesting that haemolymph oxygen affinity is adjusted to maintain optimum conditions for oxygen binding across an animal 's likely temperature range Whitely & Taylor (1993) and Whitely et al. (1995) have studied acid – base compensation in crayfish during acclimation to temperature variation occurring in natural populations and in the laboratory respectively. In in vitro and in short term laboratory studies, the pH of crustacean haemolymph varied directly with temperature. This is thought to maintain a constant relative alkalinity and net protein charges state resulting in maintained integrity of metabolic proteins. Variation of intracellular pH with temperature has been reported by the same authors, where they found that displacements of both haemolymph and intracellular pH, were much more variable in winter acclimated crayfish. Intracellular pH changes varied with the tissue studied. Tissues 62
that appeared to be metabolically important in cold acclimated crayfish maintained relative alkalinity as above, while less active tissues, such as the hepatopancreas did not, suggesting depressed metabolism in these tissues . Paglianti et al. (2004) stated that Procambarus clarkii lower metabolic sensitivity towards temperature favours its ability to survive thermal stress and is one of the biological features that explain this species invasive potential.
3.3.7.3 Compensation for high ambient acidity Many aquatic habitats have come under increasing stress by pollutants of anthropogenic origin. Crayfish are no exception. Acidification of natural waters by industrial effluent including oxides of both sulphuric and nitric acids has become a global problem and can be used as an example. Crayfish seem more tolerant to acid exposure than fish ( Jensen & Malte, 1990; Ellis & Morris 1995), but very high levels of acidity i.e. pH 2 were reported to kill crayfish in 24 h, while water pH =3 has been tolerated by more than 50 % of Procambarus clarkii for 4 days. In contrast, many fish species die in short term exposure to pH 4 i.e. 10 fold lower concentration. Some crayfish are slightly more sensitive. McMahon & Stuart (1989) observed 50% mortality in Procambarus clarkii after 60 days of exposure to pH 4. Lower acid levels may be toxic in the long term, since Abrahamsson (1972) observed some mortality of Astacus astacus exposed naturally for extended period to water of pH 5.6. Juvenile and reproductive stages and moulting animals are likely more sensitive (Wheatly & Ignaszewski, 1990). As with fish, acid stress that causes marked acidification of the haemolymph is also associated with marked ion loss from haemolymph and tissues (Mauro & Moore, 1987; McMahon & Stuart 1989). Mortality is probably more linked to the ion loss than to the haemolymph acidification. Sub-lethal exposure to pH 4 was also associated with haemolymph ion loss in chronic exposure of Procambarus clarkii to acid ( Mchahon & Stuart, 1989) although at 60 63
days exposure, both haemolymph pH and concentration of many ions had returned to levels near control animals. The latter authors compared effects of exposure to sulphuric and nitric acids. No significant difference in mortality was observed between the two acids after 6 days of exposure, but the time course and extent of the resultant haemolymph acidosis and ion loss differed substantially. McMahon & Stuart (1989) and Jensen & Malte (1990) measured ion loss from intracellular ( muscle) ion sources in Procambarus clarkii and Astacus astacus respectively, exposed to sublethal acid medium (pH 4). Astacus showed no significant changes in muscle ion levels, but ions were lost from intracellular compartments. Procambarus clarkii exhibited significant loss of all ions on initial exposure, but as with haemolymph ions all levels tended to return to control values by the end of 60 days of acid exposure. Acid exposure also affects haemolymph oxygenation.
3.3.7.3.1 Immune reactions The ability to defend the body against potential invaders of microbial origin is crucial for all living organisms, such as plants, invertebrates and vertebrate animals. This defense implies ways of distinguishing between self and non self material and organisms have evolved various elegant mechanisms to repel foreign intruders without causing harm to the body itself, from the simple way of cell communication between individual cells of yeast ( Saccharomyces cerevisiae ), where special mating type genes code for proteins that prevent them from mating with similar cells, to the sophisticated immune system of mammals that is able to recognize foreign molecules whose chemistry is only slightly different from their own. Invertebrate immune systems differ from that of vertebrates in some critical ways. First, the invertebrate immune system is innate in which the body is born with the ability to recognize and destroy certain microorganisms; second, no immunoglobulin molecules are functioning as antibodies in vertebrates (Lanz Mendoza & Faye, 1999). 64
In contrast to vertebrates, many invertebrates and all arthropods have an open vascular system that necessitates an efficient mechanism of blood clotting and wound repair. They possess white blood cells (leukocytes) which in many species are called haemocytes as they are part of the circulating haemolymph. They also lack red blood cells (erythrocytes) and instead, respiratory proteins for example haemocyanin in crayfish and other crustaceans , are responsible for carrying oxygen via the circulatory system to the tissues inside the body.
3.3.7.3.1.1 Pattern recognition protein in crayfish Crayfish are devoid of immunoglobulins, but they are still capable of responding to microbial intruders by recognizing cell wall components, such as lipopolysaccharides or peptidoglycans from bacteria and B-1, 3 –glucans from fungi. If a fungus (or a bacterium) enters the body cavity of the freshwater crayfish, B-1,3 – glucans will be released from fungal cell wall . In the haemolymph, a plasma protein called BGBP recognizes and binds to the fungal glucans and the complex will in turn bind to specific receptor on the haemocyte cell membrane and thereby activate the immune defense (Duvic & Soderhall, 1993). The proteins involved in recognition of microbial polysaccharides are called pattern recognition protein and the recognition of non self molecules by PRPs causes the initiation of several defense mechanisms (Yoshida et al., 1996).
3.3.7.3.1.2 The clotting reaction All animals either invertebrates or vertebrates, need an efficient sealing process to avoid blood loss upon injury. In arthropods, which have an open circulatory system, this is a prerequisite for their survival; accordingly different clotting systems have evolved. In the freshwater crayfish, the clotting system involves cellular as well as plasma factors. The plasma component is a very high- density lipoprotein named the clotting protein (CP) (Hall et al., 1995). The 65
crayfish CP comprises two identical subunits of 210 kDa. To induce clotting, an enzyme; Ca2+ dependent transglutaminase, localized inside the haemocytes, has to be released, as a result of wounding or microbial infection and in presence of Ca2+ in the plasma; it cross-links the CP, resulting in the formation of large chains or aggregates (Fig. 25).
3.3.7.3.1.3 Humoral defense reaction Host defense reactions in invertebrates are traditionally subdivided into physicochemical, cellular and humoral defense mechanisms, as outlined in Table (2). However, these are more or less artificial categories, since humoral factors are often of haemocyte origin and are usually necessary for the cellular defense to occur. The outer surface of the crayfish, the cuticle, is the first barrier to be penetrated by an invading microorganism, and this very hard exoskeleton offers an efficient first line of defense (Soderhall & Cerenus, 1998). If an invader succeeds in penetrating to the body cavity of the crayfish, it will have to deal with components of the crayfish humoral and cellular defense. This defense reaction is usually accompanied by blackening of the parasite in the crayfish haemolymph or in the cuticle, where it can be seen as a black spot. This phenomenon is due to melanin deposition and is a result of activity of the host enzyme phenoloxidase (PO; EC 1.14.18.1). Melanisation is an important process, not only in defense but also during wound healing and sclerotisation of the cuticle .Phenoloxidase exists in the haemolymph in an inactive form, proPO, and is the terminal enzyme of the so called proPO activating system, which is a dominating humoral defense system in the crayfish and most other invertebrates (Soderhall &Cerenius, 1998). The proPO activating system is humoral in the sense that it exerts its action outside the haemocytes, although the main components are synthesized as well as stored in their inactive forms within the haemocytes. The proPO activating system, which is released from haemocyte granules into the haemolymph upon infection, consists of several proteins such as proteinases (Wang et al.,2001), proteinase Inhibitors (Liang et al., 1997), pattern recognition molecules (Lee et al., 66
2000), and cell adhesion proteins (Johansson & Soderhall,1992), all of which exhibit their biological activity outside the haemocytes and work in concert with the haemocytes to combat an intruder . Table (2) Components of crayfish host defense system (Soderhall & Soderhall, 2002)
a) Physicochemical barrier
External skeleton Melanisation Proteinase inhibitor Chitinase inhibitors
b) Cellular
Phagocytosis Encapsulation Cytotoxicity
c) Humoral
Pro PO system Antibacterial peptides Antifungal peptides Agglutinin peptides Proteinase inhibitor
Clotting protein in plasma
Transglutaminase from haemocytes
Clot formation in the haemolymph
Fig. 25. The transglutaminase mediated clotting reaction in crayfish. Clotting protein , a dimeric protein present in plasma consisting of two identical 210 kDa subunits held together by disulphide bonds(SS), cross-linking by a haemocyte transglutaminase (TGase) in the presence of calcium ion ( Hall et al., 1995). 67
3.3.7.3.1.4 Cellular immunity In crayfish host defense, the haemocytes play a key role in immobilizing or destroying invasive microorganisms. Production of the haemocytes takes place in the haematopoetic tissues situated on the dorsal side of the stomach (Chaga et al., 1995). The haematopoetic tissues are actively proliferating tissues consisting of progenitor cells packed in sheets of connective tissues into lobules. The cells in these lobules are differentiated to varying degrees, a small portion of which can be induced to proliferate in vitro. The haemocytes of the crayfish can be grouped into three distinct subpopulations; hyaline cells, semigranular cells and granular cells. The hyaline cells, which are scarce in the crayfish (1-3%), are usually more abundant in marine crustaceans. Semigranular cells have a variable number of small granules, while granular cells are filled with numerous, highly refractive secretory granules. The cellular defense reaction in crayfish includes processes such as phagocytosis and encapsulation (Millar & Ratcliffe, 1994).Phagocytosis of foreign intruders is a phenomenon common to all animal species and is one of the important host defense reactions in invertebrates. Studies on separation of haemocytes in vitro, have revealed that in crayfish, the hyaline and a minor part of the semigranular cells are capable of phagocytosis (Soderhall et al., 1986). Certain recognition factors or opsonins present in the haemolymph (plasma) usually enhance in vivo phagocytosis. When a parasite is too large to be engulfed by phagocytotic haemocytes, these cooperate to form capsules or aggregates of cells in order to immobilize the parasites and prevent their spread in the haemcoel. This process is called encapsulation or nodule formation. The cells engaged in encapsulation and nodule formation in crayfish are the semigranular cells, which on their own can promote these reactions. The previously mentioned cell communicative protein peroxinectin that is inactivated and released from the secretory granules of the semigranular and granular cells as a result of infection, can also exhibit encapsulation promoting activity in vitro ( Kobayashi et al ., 1990) .
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Chapter 4 Feeding and culture With the expanding world population, the demand for seafood is increasing, but from where will this seafood come? The current world population of approximately 5.5 billion is expanding at an annual rate of 86 million persons a year, and this rate of increase is expected to increase largely in the new century. Increasing demand for seafood is also coming from increasing per capita consumption. More seafood is being consumed because there are more mouths to feed and because per capita consumption in many areas is increasing. The freshwater crayfish is currently the only crustacean cultured on a large- scale in United States as well as in some other countries. Some farmers rely on natural vegetation for crayfish forage, such as alligator weed (Atternanthera philoxeroides). During summer months, the crayfish remain underground in Louisiana, USA, and this is contrary to Egypt, where they remain in the burrows during winter and emerge in the spring when the water temperature increases. In the fall, from September 15 to October 15 in Louisiana, water is added to ponds, and the crayfish emerge from their burrows. Each female releases approximately 300 young which are attached to her abdomen. Young and adults begin feeding on bacteria, zooplankton, and other organisms associated with decomposition of rice forage. The potential for expansion of crayfish farming is excellent, particularly in warm temperature countries where rice is grown. In the last decade, a great market is being established for the crayfish, where increased demand for such seafood resource particularly in USA as well as in several European and Asian countries is remarkable. Moreover, soft-shell crayfish have a potential as food and as bait in sportfishing. ______________________ Amal Sobhy Ibrahim
69
Huner & Avault (1976) reported on production of soft–shell crayfish, but it was not until Cain & Avault (1983) developed the electro–trawl for harvesting soft–crayfish that became commercially feasible.
4.1 Feeding Crayfish have been classified as herbivores (vegetation eaters), detritivores or derivers (consumers of decomposing organic matter) omnivores (consumers of both plant and animal matter) and more recently, obligate carnivores, which mean that they “require” some animal matter in the diet for optimal growth and health. Crayfish have been known to ingest living and decomposing plant matter, seeds, algae, epiphytic organisms, microorganisms and an assortment of larger aquatic invertebrates such as insects and snails. They also feed on small fish when possible. These food sources vary considerably in the quantity and quality in which they are found in the aquatic habitat. Living plants often the most abundant food resource in crayfish ponds and natural habitats, are thought to contribute little to the direct nourishment of crayfish. Starchy seeds are sometimes consumed and may provide the needed energy, but intact fibrous plant matter is mostly consumed when other food sources are in short supply. Aside from furnishing a few essential nutrients, living plants matter provides limited energy and nutrition to growing crayfish (Richardson et al., 2007). Decomposing plant material with its microorganisms is consumed to a much greater degree and has a higher food value. The ability of crayfish to use detritus as mainstay food item; however appears to be very limited. Fortunately in typical crayfish pond environment, numerous animals besides crayfish rely on the microbe -rich detritus as their main food source. Molluscs, insects, worms, small crustaceans and some small vertebrates depend on detritus and when consumed by crayfish, these animals furnish high- quality nutrition. Scientists have realized that for crayfish to grow at their maximum rate, they must feed to a greater extent on these high - protein, energy -rich food sources. Sufficient 70
evidence has been established to indicate that although crayfish must consume high-protein, high - energy sources to achieve optimum growth, they can sustain themselves for some time by eating intact and decomposing plant sources and even bottom sediments containing organic debris. Supplemental feeds are not routinely provided to crayfish aquaculture ponds and commercial culture of crayfish relies on self -sustaining system for providing nourishment as occurs in natural habitats, where crayfish are abundant. An established vegetative forage crop provides the basis of a complex food web (Fig. 26) that ultimately fuels production of crayfish with harvests that typically average 400-600 pounds per acre and often exceed 1000 pounds per acre ( Richardson et al., 2007). The nutritional requirements of crustaceans and in particular of red swamp crayfish are not completely studied. The digestibility of protein in the diet of crustaceans depends mainly on the proportion of amino acids, and especially of limiting amino acids. However, the proteolitic characteristics are variable from one species to another and it is not what the optimum protein composition for red swamp crayfish is. Lipids also play an important role in the nutrition of aquatic animals, especially in decapod crustaceans which are incapable of producing linoleic and linolenic acids (Van-Wormhoudt & Bellon- Humbert, 1994). Huner & Meyers (1979) found that protein of animal origin might have a significant positive effect on the growth of juvenile red swamp crayfish. Brown et al. (1989) reported that addition of menhaden fish meal, shrimp -head meal, and peanut meal in the reference diet of adult crayfish resulted in decreased consumption and menhaden fish meal was poorly digested when incorporated at 30% in the reference diet. Apparent dry matter and energy digestion coefficients indicated that plant feedstuffs have greater potential as ingredients in crayfish diets than feedstuffs of animal origin. McClain (1995) examined the effects of late-season supplemental feeding on crayfish production and size distribution of harvested P. clarkii. The control group was managed as 71
for typical crayfish ponds, whereby crayfish relied solely on the detritalbased food system. The other group received a formulated feed (25% crude protein crayfish pellets) in addition to the detrital-based resources. They concluded that supplementing forage-based crayfish ponds with prepared feeds during the latter part of the culture season increased total annual production but failed to significantly increase the average size of harvested crayfish (Table 3). Total annual production was increased to 252 Kg /ha with supplemental feeds, as a 21% increase. Crayfish production was increased with supplemental feeding of a formulated feed; natural feeding alone had no significant impact on increasing the average size of harvested crayfish. Survival rate has been increased with supplemental feeds as observed by Villagran (1993).
Crayfish
Substrate Invertebrates
Zooplankton
Decomposing
Forage crop
vegetation
Fig. 26. A simplified diagram of the nutrient pathways of the food chain in crayfish ponds with forage crop serving as the principal fuel and crayfish at the top of the food chain (Richardson et al., 2007).
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Table 3. Mean annual yield (Kg /ha) and average weight (g) of trap-harvested crayfish from rice-planted ponds with and without supplemental feed. Means followed by same letter in a column were not significantly different (p>0. 05). Yield by Size Grade Treatment
Total annual yield
Average Weight Yield
Large (Avg. wt. 35 g)
Yield
% of Total
Medium
Small
(Avg. wt. 21 g)
(Avg. wt. 16 g)
Yield
% of Total
Yield
% of Total
Rice only
1185
17. 4
54
4. 6
370
31. 2
761
64. 2
Rice+ Feed
1437
17. 7
50
3. 5
469
32. 6
918
63. 9
4.1.1 Nutrient requirements Although little is known about the nutrient requirements of crayfish, their qualitative nutrient requirements are presumed to be similar to those of other aquatic animals. They grow satisfactorily in closed system on nutritionally complete commercial catfish feeds (Huner & Barr, 1984), which indicates that dietary allowances for catfish feed meet the nutritional requirements of crayfish. Data obtained with experimentally designed diet under laboratory conditions without natural food indicated that growth rate of red crayfish was highest at protein levels of 20% to 30% and that 15% to 20% of the protein should be of animal origin (Huner & Meyers, 1979). Growth and body composition data suggested that a diet containing 30% protein and 2,500 kcal / kg of gross energy is optimum for growth and protein deposition in red crayfish (Hubbard et al., 1985). Crayfish do not require fish meal or oils in their diet, so comparatively inexpensive pelletized feeds can also be used. Chicken and trout pellets as well as luceme blocks have been used in the past, but now a number of specialized crayfish feeds are available. Factors which are considered when choosing pelletized diets include cost, absence of pesticides and herbicides, ease of application, food conversion ratio (FCR), shelf life, particle size, attractants and acceptability, breakdown period, potential 73
and the best time (s) of day for feeding. Juveniles need small regular feeds while larger animals are fed once a day or less often. The feed rates may be varied with temperature, so generally 5% of estimated total live weight per week is good standard, which can be increased to 10% in spring. At all times, it is best to provide adequate aeration. The food is spread around the edges of ponds for foraging. Also, if the food is put around shallow sides of ponds, it enables monitoring of the feeding rates (O’Sullivan, 1995). Jover et al. (1999) conducted two nutritional trials with juvenile Procambarus clarkii, using eight cooked- extruded diets containing different levels of protein, lipid and carbohydrate. They found that the optimum nutrient levels for the crayfish growth were 2226% crude protein, 6% lipid and 36-41% carbohydrate.
4.1.2 Feeding behavior Although crayfish are indiscriminate feeders, feeds of animal origin appear to be preferred. Macro vegetation constitutes the largest portion of the detritus. They also consume tissues of green macrophytes. Crayfish are poor swimmers but they sometimes capture food at the water surface. If natural or artificial foods are taken at the surface, the crayfish then settles down to consume the captured item. Crayfish readily consume almost all species of snails, hydrophytes and fish species commonly found in nature in Egypt. Regarding the snails, the crayfish tends to be choosy when it comes to them as a food. This choice is affected by certain factors such as hardness of the shell, how fast the snail sticks to the stones, how big the snail is and how wide the aperture is in relation to the body. Regarding fish as a source of food, it was noticed by Ibrahim et al. (1995) that crayfish can devour any kind of fish depending on the facility of catching the prey. It was very difficult for the crayfish to catch live fish, but when live and dead mixed group was introduced to the crayfish, they only devoured the dead ones. Although crayfish consume detritus directly, the major source of nutrients is the detritus-based ecosystem benthic organisms, which include bacteria, protozoans, small planktonic crustaceans, molluscs, 74
and insects. These organisms are good sources of the essential nutrients. Even though animal material are important nutrient sources for crayfish, the total volume of animal material found in the stomach seldom exceeds 10% of the total food volume (Huner & Barr, 1984). Green plants are second to detritus in the volume of food consumed by crayfish. Huner & Meyers (1979) found that protein of animal origin might have a significant positive effect on the growth of juvenile red swamp crayfish. They concluded that a concentration of 15% of gross animal protein in the diet was the lowest acceptable value for feeding red swamp crayfish. Ibrahim et al. (1995) showed that the very young stages (0. 5-0. 9 cm carapace length) depend mainly on plankton as the main diet, in addition to a little amount of the aquatic plants. Medium sized crayfish (2. 0 - 4. 9 cm carapace length) prefer animal organisms in addition to the plant sources. Fish scales were found abundantly in the gut of large sized individuals (over 5cm carapace length), indicating its main dependence on fish as food. The lower predation on live fish related to the strong escape behaviour, shifts crayfish trophic strategy to detritophagy. Preference for animal food was observed when dead fish or macro-invertebrates with reduced or no swimming behaviour, and without strong flight reaction were provided. In Alentejo inland waters (Portugal), animal items were frequently observed in crayfish diets, macro-invertebrates representing approximately 20% of stomach contents (IIheu, 1991). Momot et al. (1978) reported detrital vegetation to occur with much higher incidence in the stomachs of juvenile crayfish than in adults. Wiernicki (1984) found that young P. clarkii obtained at least 50% of their carbon from detritus in the form of microorganisms and this percentage decreased as crayfish size increased. These data imply the importance of organic detritus with its associated micro-flora and -fauna to young, rapidly growing crayfish. Kreider & Watt (1998) examined the behavioral response of Procambarus clarkii to natural dietary items (zooplankton, live fishes, and fish eggs ) and common components of formulated feeds used in the aquaculture industry (soybean meal, fish meal, corn meal, alfalfa meal 75
and vitamin C). They studied the whole-animal bioassay that included the following behaviors:(1) movement of the maxillipeds for longer than three seconds, (2) increased movement of the walking legs with dactyl “probing” (3) movement of walking legs to the mouth, and (4) orientation of the entire body towards the odor source. All diets tested were significantly stimulatory. But zooplankton was the most stimulatory of the natural dietary items tested. Alcorlo et al. (2004) examined 80 stomachs of crayfish and food items were classified with relative frequencies of occurrence. The overall data for each sampling are presented in Figure 27.
Fig. 27. Frequency of occurrence of the various food categories found in the digestive tracts of Procambarus clarkii (Alcorlo et al., 2004)
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In natural freshwater marsh, P. clarkii uses higher number of food items and higher amount of animal food than in the rice field. The use of animal food in the natural marsh varied with time and reflected the availability of macroinvertebrates in the environment. In the rice field with high amounts of plant material (rice seeds and leaves of rice plants) and low macroinvertebrate diversity, animal food was less important. The pesticides extensively applied during the sowing period were found to reduce macroinvertebrates abundance and diversity in rice fields (Jimenez et al., 2003). Cannibalism is more frequent in rice fields and is probably a consequence of high crayfish densities (172. 5crayfish/trap/day; Montes et al., 2001). In high density populations, the feeding of crayfish rapidly reduces the abundance of high quality food, especially that of less mobile invertebrates. Consequently, growth rates decline, cannibalism increases, and crayfish are forced to switch to less valuable food sources (Nystrom, 2002).
4.4 Culture The origin of crayfish culture can be traced back to the late 1700s, when plantation gardeners cultured the tasty animals in small ponds as a special delight for their employers (Huner & Barr, 1991). Later, the rice farmers found that crayfish were an excellent lagniappe (bonus) crop, as they would flood their fields during the fall and winter months to attract waterfowl for hunting and to level the bottoms, crayfish would then move quickly into the predator-free ponds and thrive. Thus, when the ponds were drained in the spring, the farmers actually had a bonus crop, or lagniappe. In the early 1930s, Percy Viosca, a leading Louisiana naturalist, published recommendations for culturing crayfish in ponds (Huner & Barr, 1991). This led to a gradual interest and increase in the culture of crayfish. His interest encouraged others to develop a real industry. Currently about 125,000 acres are devoted to crayfish culture in Louisiana alone. It is estimated that from crayfish ponds in Louisiana, 77
about 230 kg per acre per year are harvested; a total of more than 28,125,000 kg of crayfish. The red swamp crayfish (P. clarkii) or crawfish as they are called commercially and the white river crayfish (P. zonangulus) are the primary species cultivated in the United States. The red crayfish is normally predominant, but the white crayfish may occur in greater numbers in some areas. Moreover, P. clarkii has been also known for its outstanding feeding capacity on some aquatic pestweeds (Groves, 1985). The culture of red crayfish was expanded to other areas including southern Texas, Florida, North and South Carolina, Arkansas, Mississippi, Georgia and Maryland. The red crayfish is cultured by establishing sustaining populations within shallow (30 to 75cm) earthen ponds. The basic pattern, as practiced in Louisiana, involves stocking with adult crayfish in late spring, draining in early summer, reflooding in early fall, and harvesting when numbers justify the effort, as early as November or as late as March. This wet/dry cycle closely simulates the natural hydrological cycle in southern Louisiana. Some red crayfish spawn in ponds in late spring or mid-summer. Unless water is present, young crayfish from such hatches remain in burrows. Numbers are not great, and absolute growth is apparently retarded by warm water temperatures (30-32°C) even though the moulting rate is rapid. Growth is also slowed in the winter when temperatures fall below 10-15°C. In regions like Texas and South Carolina, with climates similar to Louisiana's, P. clarkii has been cultured with great success by following the wet/ dry cycle employed in Louisiana. In colder regions such as Arkansas and Missouri, growth rate is greatly retarded by extended low temperatures during the winter. This prevents harvest until middle to late spring (Huner & Barr, 1991). The wet/dry cycle seems essential for several reasons since it: (1) serves to prevent the establishment of predacious fish populations; (2) phases reproductive activity of the crayfish; (3) permits the growth of 78
vegetation that will serve as food and substrate; and (4) permits the cultivation of rice as a grain product. Most aquaculture involves the stocking of known numbers of young fish or shellfish with total harvest after a period of growth. Yields can be easily predicted. In red crayfish culture, there is no simple relationship between adult crayfish stocked and yield. The artificial production of young red crayfish is possible and is practiced by several hatcheries in California.
4.2.1. Ponds types There are two broad categories of crayfish ponds, open and wooded. Most crayfish specialists would then divide these into two subcategories of wooded ponds and four subcategories of open ponds. These depend on the pond soil and the dominant vegetation. These, in turn, influence the general appearance of the water.
4.2.2. Site selection Advisory agencies advocate paid construction in areas with heavy clay or silty clay soils; that is, areas that will hold water. Areas suitable for rice production should also be suitable for crayfish if there is no residual pesticide contamination. However, success is generally assured if the area already has a resident population of red swamp crayfish and/or white river crayfish. Checking drainage ditches and canals for crayfish and looking for burrows is advisable in selecting a site for a pond. Crayfish ponds are normally built with a minimum depth of 30cm and a maximum depth of 75cm. Deeper ponds are needed in climates with greater temperature variations. The levee crown should be at least 30cm above the full water level. Levees should be wide enough to permit vehicular traffic. The earth must have enough clay in it to hold water. Sandy soils are to be avoided. It is preferable that the entire pond be drained during the summer. If there are burrow pits inside the pond, it may be impractical to drain them. Water levels inside the pits should be kept as low as possible. 79
Oxygen levels below 2 ppm can be fatal, and ponds should be monitored with oxygen kits or oxygen meters. Several factors should be remembered in checking the DO (dissolved oxygen). Early in the morning, the DO level is usually low. This reduction is caused by phytoplankton. When crayfish are found near the surface clinging to vegetation, the pond is low in oxygen. To insure minimal dissolved oxygen concentrations, one should begin to flush a pond two weeks after it is flooded. This requires a pumping rate of about 100 gallons per minute per acre for a 45cm water depth. This should continue until temperature falls below 18°C (the point at which microbial decomposition of vegetation declines markedly). Additional pumping may be needed as water temperatures rise above 18°C in the spring. Use of some semi-aquatic vegetation to provide cover and access to the surface is yet another method to reduce oxygen needs. Semi-aquatic plants like rice and alligator weed are excellent for this, because they do not die back after they are flooded. Alligator weed must be carefully controlled because it is so prolific that it can take over a pond.
4.2.3. Sources of water The best water source is a spring. Such water is normally free of pesticides and fish, and it may be high in iron content. Where water enters ponds or irrigation ditches, a reddish-brown scum may develop. This occurs when there is too much iron in the water. In such cases, the water should be allowed to run through a settling pond or across the levee before entering the pond, or should be aerated in some way. The iron is harmful because it uses up free oxygen in the water. The scum can clog crayfish gills as well as be toxic to them. Most spring water will be low in oxygen and should be splashed against some sort of flat surface to oxygenate it as it enters the pond. Such water may also be low in dissolved minerals. If alkalinity or hardness is low, the pond bottom may have to be limed. Certainly a complete water analysis should be obtained before the spring water is used for agriculture.
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4.2.4. Substrate Substrate is a surface on which an organism grows or is attached. In crayfish ponds substrates are the erect stalks of vegetation. These plants are important for several reasons. First and foremost, they increase the amount of surface area available to each crayfish. Thus the number of crayfish in a given area can be much greater than if no substrates were present. A very good analogy is the building of high-rise buildings to take advantage of limited building space in cities. Substrate, itself, provides both food and a place for epiphyton to grow. The epiphyton is an important food source for crayfish and provides a protective cover from predators. Finally, substrates provide crayfish with an avenue to the surface if oxygen levels fall dangerously low. This is especially important as crayfish cannot swim well and stay at the surface like fish.
4.2.5. Feeds and fertilizers In many aquaculture systems, artificial feeds are used to supplement the natural food supply. Formulated feeds are not used routinely in pond crayfish culture. Instead, a detritus-based ecosystem is established to provide food for the crayfish. When shallow ponds with emergent vegetation are flooded, the annual plants die back at varying rates. As they die, the plant tissue is broken down by microbial action. Initially such decomposed plant material, detritus, has a very high ratio of carbon atoms to nitrogen atoms. This is important to animals that live and feed on the detritus. As the detritus is attacked by unicellular decomposers (fungi, bacteria, yeasts, etc.), the carbon-nitrogen ratio falls from a high of 100:1 to a desirable low of 17:1. The decomposers need the carbon for their metabolism. The 17:1 ratio figure represents the point at which detritus will become an especially good food source for most detritivores such as the crayfish. The crayfish eat the microbially enriched detritus but digest only the living layer of microbes on the surface, and as the detritus is broken up, more microbes grow on it. Furthermore, surface area to volume ratio increases. 81
Green plants (including the algae in epiphyton) are essential components in the diets of healthy crayfish, which have a bright yellow hepatopancreas and well-pigmented shell. The color is derived from plant pigments called carotenoids. There has been much discussion concerning the absolute nutritional value of green plants in ponds; however, it is clear that if crayfish do not have access to such plants, they will not be healthy. This is certainly one value of alligator weed, which is common in ponds dominated by natural vegetation. All crayfish ponds support a multitude of benthic and clinging creatures, which include insects and their larvae, worms, and molluscs (mostly snails), as well as planktonic creatures like water fleas, copepods, and ostracods. These provide essential animal nutrients not otherwise available in plant foods; especially important for immature crayfish.
4.2.6. Agricultural wastes Many by-products and waste products from agricultural activity have been evaluated as crayfish feed. Among the materials tested were sugarcane (Saccharum officinarum), sugarcane bagasse, sugarcane filter cake, chicken manure, sweet potato (Ipomea batatas) trimmings and vines, rye hay (Secale cerate), soybean stubble ,and rice hay (Oryza sativa), and bahiagrass hay (Paspalum notatum). Although several of these supported crayfish growth, only the hays were found to have practical potential for large-scale commercial crayfish ponds (Huner & Barr, 1991). Hays such as rice and bahiagrass can be used to supplement food supplies in ponds when the primary vegetation in the pond becomes limited or depleted. The addition of 300- 500 pounds per acre of hay provides vegetative matter that enters the detrital food chain, thus providing suitable crayfish food. This practice although common, its efficiency is not thoroughly documented, but positive results have often been reported. There are basically two approaches to rice-crayfish culture. In the first, both rice and crayfish are raised as cash crops. Rice is planted in 82
early spring and harvested for grain in late summer. The rice stubble is left standing and ratoon growth (green regrowth) is encouraged. The field is reflooded in early autumn and crayfish subsist on the decaying rice stubble and green regrowth. In the second approach, rice is planted solely for crayfish culture, with no concern for grain production. In this strategy, rice is planted in mid to late summer and the crop, if produced, is not removed. The entire rice plant then remains to provide crayfish forage.
4.2.7. Artificial feeds Laboratory and pond studies have demonstrated that crayfish readily consume fish and crustacean feeds. The cost of artificial feeds is such that those designed specifically for crayfish have only recently been developed (Huner & Barr, 1991). They are so new, in fact, that precise recommendations and economics for pond use have not yet been refined. The basic problem is simple. There is, as yet, no way to predict the actual numbers of crayfish present in a pond because known numbers are not stocked as is the case in most forms of aquaculture. Crayfish ponds are "self stocking" and "stock" themselves over a period of several months. Furthermore, it is almost impossible to observe feeding activity, as is the case with fish systems, in which floating feeds are used. Even when crayfish densities can be predicted, feeding has not led to significant gains in the weight of individual crayfish in very dense populations, where density-dependent factors interfere with growth. Protein is the most expensive part of an artificial animal feed. It appears that in tanks and ponds, red and white crayfishes require 25-30 % protein in artificial feeds, of which 15-20 % must be of animal origin. In one laboratory study, the fastest growth and protein deposition in red crayfish were observed when they were given a protein: energy ratio of 120 milligrams of protein per kilocalorie, in a diet containing 30 % crude protein and 2.5 kilocalories per gram of dietary energy. Both red and white crayfishes are very efficient at utilizing plant proteins and carbohydrates in feeds. Lipids should probably not exceed about 6 % of 83
any artificial feed. In confined systems, crayfish on artificial feeds become very pale after several moults. If they are to retain normal pigmentation, their diets must be supplemented with a source of carotenoid pigment such as fresh, succulent plant material (elodea, alligator weed). In general, feeding rates of about 3 % of estimated body weight per day when water temperatures exceed 20-22°C produce good growth in tanks and ponds. Supplemental feeds in crayfish ponds may be effective with protein levels of 15-20 %. This is because there is much natural food in ponds. However, there is not enough experience with supplemental feeds in ponds to make any recommendations.
4.2.8. Use of fertilizers Crayfish pond production is based on the presence of a luxuriant growth of vegetation. Good management dictates that the pond soil should be fertilized in keeping with recommendations from the local extension service for growing the cover crop being employed in that pond. Naturally, a complete soil analysis should be performed on the soil before a new pond is built, and periodic checks should be made once the pond is in production. A key element in crayfish culture is calcium, as 25 to 30 % of crayfish shells are calcium. Sustained harvest of 230-460 kg of crayfish per acre per year over several seasons will obviously reduce calcium levels in the pond. It can be observed that if the soil tests show that calcium in the soil is adequate for growing a crop, such as cabbage, which requires calcium-rich soil, the application of calcium (lime) is not needed. If the soil is deficient, lime should be applied as needed. Application of chemical fertilizers to flooded ponds does not seem to benefit the crayfish production. No recommendations are available on the subject at this time. Organic fertilizers (manures) probably help, as the organic matter is eaten directly by the animals that crayfish eat (and the crayfish, too), increasing their food supply. However, there are certain aesthetic objections to such practice, though 84
it is a common aquaculture practice in other countries. This field is one that requires further study that may lead to increased production and thereby benefit farmers.
4.2.9. Pond crayfish population dynamics Ponds are managed by establishing sustaining populations. In areas with no resident red swamp crayfishes, it may take several years before good populations are established. In such areas, first year production is usually several hundred pounds per acre of very large crayfish. Production can reach 460 kg or more per acre of smaller but very nice crayfish in the second or third year. In areas with resident crayfish populations, production is usually high in the first year but size is moderate. Farmers report more frequently now poor production after a year of producing 460-920 kg per acre. This seems to be associated with many small crayfish. That is, reproductive success of surviving brood stock was so great that high densities inhibit growth. Density should be reduced to enhance growth rates but prices for the small crayfish are so low that the farmers do not harvest then, compounding the problem. Planning economics on yields over 275 kg per acre is not advisable. The development of a computer simulation model of crayfish pond population dynamics is a major first step in effective crayfish pond management.
4.2.10. Stocking Crayfish yields of 460 to 690 kg per acre per year are considered to be attainable in well-managed ponds (Huner & Barr, 1991). A little constructive computation reveals that 3 - 6 kg of female crayfish are all that are needed to produce that sort of crop. The average crayfish used for stocking is 7.5 to 10 cm long. A female of that size can produce about 300 young. About 60 % of these can be expected to survive to be harvested in a good pond. Considering that 20,000 crayfish at a weight of 44 per kg must be harvested to obtain a yield of 460 kg per acre, 144 85
females are required per acre. At 44 per kg, the total weight of required females is slightly more than 3.2 kg. As the male-female ratios are normally 1 to 1, stocking 9 kg per acre should be adequate for any pond. Some crayfish must be left in the pond to produce young for the next year. In controlled hatchery systems, it was noted the following results with various ratios of males to females. When there are a greater number of males to females, females are damaged and their mortality is high. A greater number of females to males results in low egg production. The best ratio is 1:1(Huner & Barr, 1991). Thus, a pond should be checked for the presence of crayfish sex ratio before it is stocked. The key is survival of the broodstock. With reduced amounts of cover (vegetation such as water hyacinth and alligator weed mats, existing holes or depressions, or relatively flat objects, piece of tin, boat, or log), their chances for survival are reduced drastically. Production of less than 460 kg per acre per year can be a result of low reproduction in ponds, assuming that harvesting is intensive and poor water quality or fish do not kill young-of-the-year crayfish. As production can approach 920 kg per acre per year in extremely well-managed ponds, the need for improving the survival of broodstock seems to be warranted. Another reason for poor production is too many crayfish. That is, growth is density dependent, and when there are too many young, none grow very well. So, how many are too many? This depends on the amount of forage, vertical substrate in the pond, water quality, and harvesting activity. Unfortunately, scientists have not yet worked out the relationships between densities and these factors. Production has reached 1840 kg per acre. At 20 crayfish per pound, density would be around 80,000 per acre. However, this is probably the upper limit with lower densities needed to insure production of 44 per kg for larger crayfish. Crayfish take 12 to 48 hours to dig a hole that is deep enough to protect them from predators. Observations of crayfish ponds and natural 86
areas have shown that wherever there is cover, crayfish will burrow successfully. We believe that farmers could facilitate the burrowing process and thereby improve production by starting holes with a pole around the edge of the pond and placing some form of inexpensive cover such as heavy cardboard or old boards on them. The usefulness of these procedures in established ponds is debatable. If water quality is good and there are no fish problems, they would probably be useful in established ponds where production is not good, especially those with little cover when they are drained.
4.2.11. Care of brood crayfish Crayfish that will be stocked in ponds should be stocked within several hours of capture. They should not be refrigerated but kept shaded and moved early in the morning, late in the afternoon, or at night. They should experience as little stress as possible. Cooling to about 10 to 16°C for long distance shipments is advisable, but the crayfish should be warmed slowly before stocking. It is also better to stock crayfish in the center of the pond, to discourage their crawling out of the pond. If crayfish have been out of the water for a long time, their gill chambers may be full of air. They will float when put into deep water and may be unable to reestablish water flow over the gills. If this is the case, they must be allowed to walk into the pond so that they can refill their gill chambers (Huner & Barr, 1991). When crayfish are moved, their gill chambers must remain moist. Crayfish can have moist air in the chambers, but if the gills dry, the crayfish will dehydrate. Moist packing material, like newspaper, sponge rubber, and shavings, and/or periodic showers of water must be employed. There is much doubt about the effects of shipping on brood crayfish. It is recommend that brood crayfish be shipped in water, either in plastic bags filled with oxygen or in regular fish-hauling tanks. Otherwise, females under stress often reabsorb their developing eggs. Further research is certainly needed to establish the most effective and least expensive methods of shipping brood crayfish. 87
Chapter 5 Economic importance and safety for consumers The crayfish Procambarus clarkii has rapidly expanded in all freshwater ecosystems including streams, ponds and marshes with polluted or clean waters, with outstanding power to adapt to new habitats and became an important component of the local aquatic fauna (Soliman et al., 1998 a & b; Hamdi, 2004). P. clarkii now represents a problem to the Egyptian fishermen, farmers and for the River Nile environment; and also has a serious effect on the aquaculture development in Egypt. It causes a lot of damage to the fisheries of the Nile possibly by attacking the fry and damaging the nets of the fishermen (Soliman et al., 1998b). Also, their burrowing activity has caused considerable agricultural damage primarily to irrigation constructions such as dams and levees. They are also said to destroy the roots and shoots of some crops. Recent studies also recorded that it eats frogs eggs and young. Thus, it represented a new challenge to the local environment. However, as happened in other countries, it could be biologically managed through fishing and consumption as cheap food that can contribute to aquatic animal proteins. A Comparative study was carried out on two high priced marine shrimps namely: Penaeus japonicus and Penaeus semisulcatus and the present crayfish. The former shrimp was obtained from Lake Qarun, while the second from the Suez Gulf (Hamdi & Zaghloul, 2006). This study proved that the abdominal meat of the crayfish P. clarkii is not only delicious but extremely nutritive. Moreover, it is an excellent source of protein with lower amount of fat than both Penaeus japonicus and P. semisulcatus (Table 4) and includes vital minerals such as Na, K, Ca, Mg, P and selenium (Figs. 28-33). This confirms the finding of Hafez et al. (2003) on the presence of such minerals in P. clarkii. __________________________________________________ Salwa Abd El Hamid Hamdy 88
Table (4): Biochemical composition of the meat yield of Procambarus clarkii in comparison with the two marine shrimps. Water content (%)
Crustacean Species
Total protein (% of Dry Wt)
Total lipids (% of Dry Wt)
Ash (% of Dry Wt)
Gross Energy (Kcal/100g)
Male
Female
tv
Male
Female
P. clarkii
78.4 ± 0.13 B
79.7 ± 0.6 A
8**
43.8 ± 0.15 B
41.2 ± 0.29 C
P. japonicus
79.1 ± 0.1 A
79.7 ± 0.17 A
3.2*
54.02 ± 0.04 A
49.2 ± 0.57 B
8.4**
P. semisulcatus
78.2 ± 0.2 B
80.02 ± 0.11 A
8.1*
54.1 ± 0.1 A
51.4 ±0.32 A
8.4**
F-value
15.3**
1.67
4077**
167**
tv
Female
tv
Male
Female
tv
Male
Female
12.9 ± 0.1 B
2.8*
39.7 ±0.39 A
42.1 ±0.08 A
5.96**
376
357
16.5 ± 0.14 A
15.8 ± 0.06 A
5.1**
29.3 ±0.11 B
30.9 ±0.27 B
5.3**
465
430
16.4 ± 0.05 A
15.7 ± 0.08 A
8.4**
29.3 ±0.12 B
29.9 ±0.09 C
464
442
338**
413**
610**
1508**
Male
13.3 7.8** ± 0.09 B
- Data are represented as means of ten samples ± S.E. - tv = t test between male and female individuals of each species for each parameter. - Means with the same letter for each parameter are not significantly different, otherwise they do. * Significant difference (P Helwan > Al-Sharqia). This might be attributed to an increased synthesis of acute phase proteins (new polypeptide chain) which act as buffer or as protective proteins against toxicity with heavy metals (Gewurz, 1982). In conclusion, P.clarkii can be used as a bioindicator of water pollution. Further, in view of its remarkable ability to excrete heavy metal pollutants up to certain levels, it could be safely consumed as a source of food to cross the gap in protein deficiency. However, it is advisable for collection of such crayfish, that it should be restricted to clean freshwater habitats to secure biosafety for human health.
108
Table 9. Water quality and heavy metal concentrations of water samples collected from the four studied areas. Water quality Sites Conductivity (MS)
ElSharqia
Helwan ElFayoum AboRawash
2360.00 ± 5.00 B 939.00 ± 2.00 D 9570.00 ± 3.000 A 1305.00 ± 0.000 C 999.9**
Salinity
Hardness
pH
ppt (mg/l)
ppt (mg/l)
5.37 ± 0.005 D 6.48 ± 0.010 A 5.69 ± 0.005 C 6.26 ± 0.005 B 599.1**
4.90 ± 0.100 B 0.200 ± 0.000 D 13.70 ± 0.100 A 3.90 ± 0.050 C 581.4**
474.00 ± 1.000 B 215.00 ± 0.000 D 796.00 ± 1.000 A 403.00 ± 0.000 C 999.9**
Heavy metal concentrations (ppm) Cu Zn Pb Cd Pl. = Pl. = Pl. = Pl. = 1.00 5.00 0.05 0.01 0.059 ± 0.005 A 0.024 ± 0.001 B Nil C Nil C
0.665 ± 0.001 A 0.051 ± 0.001 C 0.037± 0.001 D 0.061 ± 0.001 B 999.9**
0.163 ± 0.001 A Nill D 0.081 ± 0.001 C 0.018 ± 0.001 C 200.4**
0.013 ± 0.001 A 0.003 ± 0.001 C 0.017 ± 0.001 A 0.012 ± 0.001 B 132.7**
611.6** F-test Pl : Permissible limit (WHO, 1984). MS : Mmhos. Data are represented as means of ten samples + S.E. Means with the same letter for each parameter are not significantly different, otherwise they do. ** Highly significant difference at P0.05). 131
During the first stage, the crayfish juveniles were fed on the six formulated forages for 23 weeks. The amount of energy consumed during this stage could be determined by multiplying the amount of food eaten by the crayfish during the experimental period from each forage by its corresponding energy value. Table 23. The energy form values reported from the analysis of the formulated 6 diets prepared for feeding P. clarkii .
Forages F1 F2 F3 F4 F5 F6
Gross Energy (Kcal/g) 4.04 + 0.1 3.73 + 0.4 3.46 + 0.3 3.56 + 0.2 3.66 + 0.2 3.76 + 0.3
Digestible Energy (Kcal/g) 3.03 + 0.05 2.80 + 0.03 2.59 + 0.1 2.67 + 0.08 2.74 + 0.09 2.82 + 0.05
Digestibility % 75.01 + 0.6 75.59 + 7.3 75.07 + 3.6 75.07 + 1.9 74.92 + 1.6 75.25 + 3.6
The average amount of food consumed by the crayfish ranged from 1.7 + 0.9 g/day for forage (F1) to 1.16 + 0.7 g/day for forage (F4). The average amount of food consumed was 1.55 + 0.8 g/day, which adds to 238.7g as total food during the experimental period. Accordingly, the amount of energy consumed by the crayfish ranged from 826 to 964.4 Kcal with an average of 883.6 + 70 kcal. The second stage included the production of crayfish meat product (edible part) and the by-product (carcass). The amount of energy equivalent for the whole body according to the results of analysis is presented in Table (24).
132
Edible part
Poultry food additives
Fig.52. Flowchart showing the energy flow and conversion within the present experiment.
133
Table 24. Results of energy analysis of the whole body of crayfish after feeding on the formulated forages.
Forages F1 F2 F3 F4 F5 F6
Gross Energy (Kcal/g) 3.48 + 0.8 2.92 + 0.9 2.67 + 0.2 2.84 + 0.1 2.94 + 0.5 3.58 + 0.4
Digestible Digestibility % Energy (Kcal/g) Energy 2.61 + 0.06 77.51 + 16.5 2.91 + 0.7 101.18 +7.5 2.00 + 0.4 74.43+ 9.4 2.13 + 0.2 74.89 + 4.4 2.20 + 0.9 72.74+ 18.5 2.68 + 0.8 73.80+ 14.1
The data concerning the weight gained by crayfish fed on the different forages indicated that the weight difference of the crayfish ranged from 11.21 to 13.32 g, with an average weight of 12.32 + 1.2 g during the experimental period. Accordingly, the amount of energy within the crayfish body ranged from 31.84 to 46.53 Kcal, with an average of 37.96 + 6.1 Kcal. For the preparation of stage three, the animal was separated into two parts: the edible part and by-product carcass. The data concerning the energy found in the two parts presented in Table (25), show no significant differences between the two parts concerning the energy content. Table 25. Results of energy analysis of the two body parts of P. clarkii fed on Forage F5.
Forages Edible part Carcass
Gross Energy (Kcal/g)
Digestible Energy (Kcal/g)
Digestibility %
3.01 + 0.1
2.26 + 0.8
74.54 + 24.11
2.99 + 0.8
2.25 + 0.9
73.34 +10.86
134
Examination of the percentage of the edible and non-edible parts to the total weight showed that the average of the non-edible part represents 38.03%, while the edible part represents 61.97% of the crayfish body. So, for animal of 13.26 g final weight, the carcass represents 5.04g, while the edible part equals to 8.22 g, which represents 15.1 kcal and 24.74 Kcal respectively. In the fourth stage of this experiment, only 3% of the poultry food was crayfish by-product, which equals 30 g /kg of the forage. The measurements of the poultry diet gross energy showed that it contains 3.00 + 0.9 Kcal/g for starter and 3.00 + 0.5 Kcal/g for grower compared to control diet, which contained 3.1 + 0.1 Kcal/g for starter and 3.00 + 0.3 Kcal/g for grower (Table 26). The amount of food consumed by the chicks during starter stage (25 days) averaged 2270.83 + 500 g for the control group, while for crayfish fed chicks, it was 2291.67 + 300 g. In case of growers, the food intake during this period (13 days) averaged 2187.5 + 400g for the control, while it was 2208.33 + 250g for those fed on crayfish containing diet. Data in Table (26) showed that the energy consumed by chicken at starter period averaged 7039.57 + 1550 Kcal for the control, diet and 6875.01 + 900 Kcal for those fed on crayfish diet. Meanwhile, at the grower period, the amount of energy consumed was higher at the crayfish fed group, being 6624.99 + 750 Kcal compared to 6562.5 + 1200 Kcal in case of control diet. The data showed that the mount of chicken meat evolved in the current experiment averaged 394.6 + 50 g in control starter group and 416.67 + 70 g in crayfish fed starter group. However, for the grower group fed on control diet, the average amount of meat obtained was 604.5 + 65g, while for those fed on crayfish; the average was 867.5 + 55g. The energy equivalent for the amount of meat produced was calculated according to the finding of Leeon et al. (1996), where one g of chicken meat equals 1300 cal as presented in Table (26).
135
Table 26. Results of energy analysis for the starter and grower chickens fed on normal diet and diet containing crayfish. Parameters /Stage Food intake (g) Gross Energy(Kcal/g) Energy consumed (Kcal.) Final weight Amount of chicken meat (g) Energy equivalent (Cal/g) Total Energy gained (Kcal.)
Starter Control Crayfish 2270.83 + 2291.67+ 500 300
Grower Control Crayfish 2187.5 + 2208.33 + 400 250
3.1 + 0.1 7039.57 + 1550 818.75 + 40
3 + 0.9 6875.01 + 900 864.58 + 50
3 + 0.3 6562.5 + 1200 1600+ 200
3 + 0.5 6624.99 + 750 1800 + 200
394.6 + 50
416.67 + 70
604.5 + 65
867.5 + 55
1300
1300
1300
1300
512.98
541.67
785.85
1127.75
6.14 Economical Evaluation From the economic point of view, the cost of the crayfish diet formulation using 20 % of the forage (F2) added to 80% vegetable byproduct forage (F3) can be about 1172 LE. The ingredients suggested in the current work, including the vegetable by-product, could reduce the value of the ton by about 80 %. This is evident from the back calculations, where the ton of forage (F2) costs about 5860 + 140 LE, including 20 % protein. The amount of one ton of the formulated diet can help in producing about 60 Kg of crayfish, which amount to about 5000 individuals of 12g each, that might equal to 900 LE if sold in the market as human food (average price 15-17LE/Kg). Meanwhile, this amount could be separated to form about 22 Kg of carcass and 38 Kg of edible meat. The amount of carcass produced can be involved in production of 711.3 Kg of broiler diet (3% crayfish). In this case, the amount of crayfish used to substitute fish meal in the broiler diet equals to about 300 LE per ton. 136
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أﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ.......ﺣﯿﻮان ﻗﺸﺮي دﺧﯿﻞ ﻋﻠﻰ اﻟﺒﯿﺌﺔ اﻟﻤﺼﺮﯾﺔ ﻓﻲ اﻟﻌﻘﺪ ﻗﺒﻞ اﻷﺧﯿﺮ ﻣﻦ اﻟﻘﺮن اﻟﻌﺸﺮﯾﻦ ﻇﮭﺮ ﻓﻲ ﻣﯿﺎه اﻟﻨﯿﻞ ﺑﻤﺼﺮ ﻧﻮع ﻣﻦ ﻗﺸﺮﯾﺎت اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ،اﻧﺘﺸﺮ ﺑﺸﻜﻞ ﺳﺮﯾﻊ ﻋﻠﻰ ﻃﻮل ﻣﺠﺮى ﻧﮭﺮ اﻟﻨﯿﻞ و ﻓﺮوﻋﮫ ،ﺣﯿﺚ ﺗﻢ رﺻﺪه ﻓﻲ أﻛﺜﺮ ﻣﻦ ﻣﻜﺎن ،و ﺳﺒﺐ ﻛﺜﯿﺮا ﻣﻦ اﻟﻤﺸﺎﻛﻞ ﻟﻠﺼﯿﺎدﯾﻦ و ﻟﻠﺜﺮوة اﻟﺴﻤﻜﯿﺔ ،وأﯾﻀﺎ ﻟﺸﺒﻜﺔ اﻟﺮي ﻓﻲ ﻋﺪة ﻣﻨﺎﻃﻖ وﻗﺎم ﻛﺜﯿﺮ ﻣﻦ اﻟﺼﯿﺎدﯾﻦ ﻓﻲ اﻟﻤﺤﺎﻓﻈﺎت اﻟﻤﺨﺘﻠﻔﺔ ﺑﺘﻘﺪﯾﻢ ﺷﻜﺎوى إﻟﻰ وزﯾﺮ اﻟﺰراﻋﺔ ،وﺗﻢ ﺗﺒﻠﯿﻎ ھﯿﺌﺔ اﻟﺜﺮوة اﻟﺴﻤﻜﯿﺔ ﺑﺎﻟﺨﺴﺎﺋﺮ اﻟﻜﺒﯿﺮة اﻟﺘﻲ ﺳﺒﺒﮭﺎ ھﺬا اﻟﺤﯿﻮان ﻟﻠﺼﯿﺎدﯾﻦ وﻗﺪ ﺗﺒﯿﻦ أﻧﮫ ﺣﯿﻮان ﻏﺎز ﻟﻜﺜﯿﺮ ﻣﻦ اﻟﺒﯿﺌﺎت ﻓﻲ ﻛﺜﯿﺮ ﻣﻦ دول اﻟﻌﺎﻟﻢ ﺣﺘﻰ أﺻﺒﺢ ﻋﺎﻟﻤﻲ اﻻﻧﺘﺸﺎر. ﻟﺬﻟﻚ ﻓﻘﺪ ﺗﻢ اﻟﺘﻌﺎون ﺑﯿﻦ اﻟﺠﻤﻌﯿﺔ اﻟﻤﺼﺮﯾﺔ ﻟﺘﻨﻤﯿﺔ اﻟﺜﺮوة اﻟﺴﻤﻜﯿﺔ وﻣﻘﺮھﺎ ﻛﻠﯿﺔ اﻟﻌﻠﻮم ﺟﺎﻣﻌﺔ ﻋﯿﻦ ﺷﻤﺲ وھﯿﺌﺔ اﻟﺘﺮاﺑﻂ ﺑﯿﻦ اﻟﺠﺎﻣﻌﺎت اﻟﻤﺼﺮﯾﺔ واﻷﻣﺮﯾﻜﯿﺔ ﻓﻲ ﻣﺸﺮوع ﺑﺤﺜﻲ ﻋﺎم 1997ﻋﻘﺪ ﺑﯿﻦ ﺟﺎﻣﻌﺔ ﻋﯿﻦ ﺷﻤﺲ وﺟﺎﻣﻌﺔ ﺗﻜﺴﺎس ﺑﺎﻟﻮﻻﯾﺎت اﻟﻤﺘﺤﺪة اﻷﻣﺮﯾﻜﯿﺔ ﻟﺪراﺳﺔ ﻣﺪى اﻧﺘﺸﺎر ھﺬا اﻟﺤﯿﻮان اﻟﺪﺧﯿﻞ ﻓﻲ اﻟﺒﯿﺌﺔ اﻟﻤﺼﺮﯾﺔ واﻟﻜﺸﻒ ﻋﻦ ﻛﯿﻔﯿﺔ اﻻﺳﺘﻔﺎدة ﻣﻨﮫ وﻃﺮق اﻟﺘﻐﻠﺐ ﻋﻠﻰ ﺳﻠﺒﯿﺎﺗﮫ اﻟﺘﻲ ﺑﺪأت ﺗﻈﮭﺮ وﺗﺆﺛﺮ ﻋﻠﻰ اﻟﻤﺴﻄﺤﺎت اﻟﻤﺎﺋﯿﺔ ﺑﻤﺼﺮ. وﺗﻢ ﻣﻦ ﺧﻼل ھﺬا اﻟﻤﺸﺮوع زﯾﺎرة ﻣﺮﻛﺰ ﺑﺤﺜﻲ ﻣﺘﺨﺼﺺ ﻟﺪراﺳﺔ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻓﻲ وﻻﯾﺔ ﻟﻮﯾﺰﯾﺎﻧﺎ اﻷﻣﺮﯾﻜﯿﺔ يﻋﻤﻞ ﻋﻠﻰ زﯾﺎدة إﻧﺘﺎج ھﺬا اﻟﺤﯿﻮان ﻓﻲ ﺑﯿﺌﺘﮫ اﻟﻄﺒﯿﻌﯿﺔ وﻣﻦ ﺧﻼل اﻟﻤﺰارع اﻟﻤﺎﺋﯿﺔ أﯾﻀﺎ ....ﺣﯿﺚ ﺗﻢ ﻟﻘﺎء ﻋﺪد ﻣﻦ اﻟﺨﺒﺮاء اﻟﺬﯾﻦ ﯾﻌﻤﻠﻮن ﻓﻲ ھﺬا اﻟﻤﺮﻛﺰ وزﯾﺎرة ﻣﻌﺎﻣﻠﮭﻢ، وﻋﻠﻰ رأﺳﮭﻢ ﺑﺮوﻓﯿﺴﻮر Hunerﻣﺪﯾﺮ اﻟﻤﺮﻛﺰ واﻟﺬي ﯾﻌﺘﺒﺮ راﺋﺪ ﺑﺤﻮث اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻓﻲ اﻟﻮﻻﯾﺎت اﻟﻤﺘﺤﺪة اﻷﻣﺮﯾﻜﯿﺔ ورﺋﯿﺲ اﻻﺗﺤﺎد اﻟﺪوﻟﻲ ﻟﻌﻠﻮم اﻻرﺑﯿﺎن ﻣﻨﺬ ﻋﺎم ....1972وﻛﺎﻧﺖ ﻛﻠﻤﺘﮫ اﻟﺸﮭﯿﺮة ﻟﻨﺎ واﻟﺘﻲ ﻏﯿﺮت ﻣﻦ اﺗﺠﺎه ﺗﻔﻜﯿﺮﻧﺎ اﻟﻌﻠﻤﻲ واﻟﺒﺤﺜﻲ ﺗﺠﺎه ھﺬا اﻟﺤﯿﻮان؛ وھﻰ " أن اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻗﺪ دﺧﻞ ﻧﮭﺮ اﻟﻨﯿﻞ وﺳﻮف ﻻ ﯾﺨﺮج ﻣﻨﮫ أﺑﺪا...ﺣﺎوﻟﻮا أن ﺗﺘﻐﻠﺒﻮا ﻋﻠﻰ ﺳﻠﺒﯿﺎﺗﮫ ﻋﻦ ﻃﺮﯾﻖ اﺳﺘﻐﻼل اﯾﺠﺎﺑﯿﺎﺗﮫ" .وﺑﺎﻟﻔﻌﻞ ﻛﺎﻧﺖ أﻣﺎﻣﻨﺎ ھﺬه اﻟﻤﻘﻮﻟﺔ اﻟﺘﻲ رﺳﻤﺖ وﺧﻄﻄﺖ ﻟﺒﺤﻮث اﻟﻤﺸﺮوع. وﻋﻦ ﻛﯿﻔﯿﺔ دﺧﻮل ھﺬا اﻟﺤﯿﻮان اﻟﻘﺸﺮي إﻟﻰ ﺑﯿﺌﺘﻨﺎ اﻟﻤﺼﺮﯾﺔ ،ﺗﺒﯿﻦ ﺑﺎﻟﺪراﺳﺔ واﻟﺒﺤﺚ أﻧﮫ دﺧﻞ ﺧﻼل ﻓﻲ ﻣﻨﻄﻘﺔ ﻋﺎم 1983وﻟﻢ ﯾﺠﻠﺐ إﻟﯿﮭﺎ ﺑﻄﺮﯾﻖ ﻣﺸﺮوع ،ﺑﻞ أن أﺣﺪ أﺻﺤﺎب اﻟﻤﺰارع اﻟﺴﻤﻜﯿﺔ اﻟﺠﯿﺰة ﻗﺪ ﺟﻠﺒﮫ ﻣﻦ اﻟﺨﺎرج ﻋﻠﻰ أﺳﺎس أﻧﮫ ﺟﻤﺒﺮي ﻣﯿﺎه ﻋﺬﺑﺔ ،وﻟﻤﺎ ﻧﻤﺎ وﻇﮭﺮ ﺷﻜﻠﮫ اﻟﻤﻐﺎﯾﺮ وﻛﻼﺑﺎﺗﮫ اﻟﻘﺎﺑﻀﺔ اﻟﻀﺨﻤﺔ ﺗﺨﻠﺺ ﻣﻨﮫ ﺑﺈﻟﻘﺎﺋﮫ دون وﻋﻰ أو ﻣﺴﺌﻮﻟﯿﺔ ﻓﻲ ﻣﯿﺎه ﻧﮭﺮ اﻟﻨﯿﻞ ﻗﺮب اﻟﺠﯿﺰة وﻣﻨﮭﺎ ﺗﺴﺮب ﻣﻊ ﺗﯿﺎر اﻟﻤﺎء إﻟﻰ ﺷﺒﻜﺔ اﻟﺮي ﺑﻤﺤﺎﻓﻈﺎت اﻟﺪﻟﺘﺎ ﺟﻤﯿﻌﺎ ﺛﻢ اﺗﺠﮫ ﻟﯿﺴﯿﺮ ﻋﻜﺲ اﻟﺘﯿﺎر ﻓﻲ اﺗﺠﺎه ﻣﺤﺎﻓﻈﺎت اﻟﺼﻌﯿﺪ وﺳﺠﻞ ﻣﻨﮫ ﺟﻤﺎﻋﺎت ﻛﺒﯿﺮة ﺑﻌﺪ ذﻟﻚ ﻓﻲ اﻟﻔﯿﻮم وﺑﻨﻲ ﺳﻮﯾﻒ واﻟﻤﻨﯿﺎ ﺛﻢ ﻓﻲ أﺳﯿﻮط وﻗﻨﺎ إﻟﻰ ﺑﺎﻗﻲ ﻣﯿﺎه ﻧﮭﺮ اﻟﻨﯿﻞ ﺣﺘﻰ أﺳﻮان ﻛﻤﺎ ﺗﻢ رﺻﺪ ﺟﻤﺎﻋﺎت ﻣﺤﺪودة ﻣﻨﮫ ﻓﻲ ﺑﻌﺾ ﻗﻨﻮات اﻟﺮي ﺑﻮﺳﻂ ﺳﯿﻨﺎء ﻣﺆﺧﺮا. وﻓﻲ اﻟﺒﺪاﯾﺔ ﺗﻢ اﻟﺘﻌﺮف ﻋﻠﻰ ﻧﻮﻋﯿﻦ ﻣﻦ ھﺬا اﻟﺤﯿﻮان ﻓﻲ ﻣﯿﺎه اﻟﺪﻟﺘﺎ ھﻤﺎ: اﺳﺘﺎﻛﻮزا اﻟﻤﺴﺘﻨﻘﻌﺎت اﻷﺣﻤﺮ Red Swamp Crayfish, Procambarus clarkii 154
واﻷﺳﺘﺎﻛﻮزا اﻟﻨﮭﺮي اﻷﺑﯿﺾ White River Crayfish, Procambarus zonangulus وﻣﻮﻃﻨﮭﻤﺎ اﻷﺻﻠﻲ ھﻮ ﺟﻨﻮب اﻟﻮﻻﯾﺎت اﻟﻤﺘﺤﺪة اﻷﻣﺮﯾﻜﯿﺔ ووﺳﻂ وﺷﻤﺎل أﻣﺮﯾﻜﺎ اﻟﺠﻨﻮﺑﯿﺔ . وﻗﺪ ﺗﻢ ﻣﻦ ﺧﻼل اﻟﻤﺸﺮوع ﺗﺴﺠﯿﻞ وﺟﻮد ﻧﻮﻋﻲ اﻻﺳﺘﺎﻛﻮزا ﻣﺘﻼزﻣﯿﻦ ﻓﻲ ﻛﺜﯿﺮ ﻣﻦ ﻣﻨﺎﻃﻖ اﻟﺪﻟﺘﺎ ، وﻟﻜﻦ ﻛﺜﺎﻓﺔ اﻟﻨﻮع اﻷﺣﻤﺮ ﻛﺎﻧﺖ أﻋﻠﻰ ﺑﻜﺜﯿﺮ ﻣﻦ اﻷﺑﯿﺾ ،وﺑﻌﺪ ﻋﺎﻣﯿﻦ أﺧﺘﻔﻲ ﺗﻤﺎﻣﺎً اﻟﻨﻮع اﻷﺧﯿﺮ ﻟﻌﺪم ﯾﻼﺋﻤﮭﺎ اﻟﻨﻮع اﻷﺧﺮ اﻟﻤﻌﺮوف ﺑﺎﺳﺘﺎﻛﻮزا ﺗﻮاؤﻣﮫ ﻣﻊ ﺑﯿﺌﺔ اﻟﻤﯿﺎه ﻏﯿﺮ اﻟﺠﺎرﯾﺔ ﻓﻲ ﻧﮭﺮ اﻟﻨﯿﻞ واﻟﺘﻲ اﻟﻤﺴﺘﻨﻘﻌﺎت .وأوﺿﺤﺖ اﻟﺪراﺳﺔ أﯾﻀﺎً أن ﺑﯿﺌﺔ ﻧﮭﺮ اﻟﻨﯿﻞ أﻓﻀﻞ ﻟﻤﻌﯿﺸﺔ ھﺬا اﻟﺤﯿﻮان ﺣﺘﻰ ﻋﻦ ﻣﻮﻃﻨﮫ اﻷﺻﻠﻲ ،ﺣﯿﺚ أﺻﺒﺢ أﻛﺜﺮ ﺧﺼﻮﺑﺔ ﻓﻲ اﻟﺒﯿﺌﺔ اﻟﺠﺪﯾﺪة. و ﯾﺘﺮاوح وﺗﻀﻊ أﻧﺜﻲ اﻻﺳﺘﺎﻛﻮزا ﺑﯿﻀﮭﺎ ﻣﺮﺗﯿﻦ ﻓﻲ اﻟﻌﺎم .ﻓﻲ ﻣﻨﺘﺼﻒ أﺑﺮﯾﻞ وﻣﻨﺘﺼﻒ ﻧﻮﻓﻤﺒﺮ ، ﻋﺪده ﺑﯿﻦ 600 – 200ﺑﯿﻀﺔ ،ﺛﻢ ﺗﺪﺧﻞ اﻷﻧﺜﻰ ﻓﻲ ﻗﻨﻮات ﻣﺘﺸﺎﺑﻜﺔ ﺗﺤﻔﺮھﺎ ﻓﻲ ﺟﺴﻮر اﻟﻘﻨﻮات اﻟﺘﻲ ﺗﻌﯿﺶ ﻓﯿﮭﺎ و يﺻﻞ ﻃﻮﻟﮭﺎ إﻟﻲ ﻣﺘﺮ ﺣﺘﻰ ﻣﺘﺮﯾﻦ وﻧﺼﻒ ،وﯾﻔﻘﺲ اﻟﺒﯿﺾ إﻟﻰ اﻟﺼﻐﺎر ﻣﺒﺎﺷﺮة ﺑﻌﺪ ﺣﻮاﻟﻲ أﺳﺒﻮﻋﯿﻦ. واﻧﺘﺸﺎره اﻟﻤﺘﺴﺎرع ﻓﯿﮭﺎ -إﻟﻰ وﯾﻌﺰى ﻧﺠﺎح ھﺬا اﻟﺤﯿﻮان اﻟﺪﺧﯿﻞ ﻓﻲ ﻏﺰو اﻟﺒﯿﺌﺔ اﻟﻤﺎﺋﯿﺔ اﻟﻤﺼﺮﯾﺔ ﺗﻜﻮﯾﻦ ﻋﺸﺎﺋﺮ ﻛﺒﯿﺮة ﻣﺴﺘﺪﯾﻤﺔ ﻓﻲ ﻧﮭﺮ اﻟﻨﯿﻞ ،ﻣﻊ ﻣﻘﺎوﻣﺘﮫ ﻟﻠﺠﻔﺎف ﻋﻨﺪﻣﺎ ﯾﺨﺘﺒﺊ ﻓﻲ اﻟﺤﻔﺮ اﻟﻤﺸﺎر إﻟﯿﮭﺎ ، وﻃﺮﯾﻘﺔ ﻏﺬاﺋﮫ اﻟﺮﻣﯿﺔ واﻟﻤﺘﻨﻮﻋﺔ ،وﺳﺮﻋﺔ ﻧﻤﻮه ،وﺧﺼﻮﺑﺘﮫ اﻟﻌﺎﻟﯿﺔ وﻣﻘﺎوﻣﺘﮫ ﻟﻸﻣﺮاض واﻟﻄﻔﯿﻠﯿﺎت . وﻗﺪ ﺻﻤﻤﺖ ﻋﺪة ﺗﺠﺎرب ﻣﻌﻤﻠﯿﺔ ﻟﺪراﺳﺔ اﻟﺴﻠﻮك اﻟﻐﺬاﺋﻲ ﻟﮭﺬا اﻟﺤﯿﻮان اﻟﻘﺸﺮي اﻟﺪﺧﯿﻞ ،أﺳﺘﻨﺘﺞ ﻣﻨﮭﺎ أﻧﮫ ﯾﺴﺘﻄﯿﻊ اﻟﺘﮭﺎم أﻧﻮاع ﻣﺨﺘﻠﻔﺔ ﻣﻦ اﻟﻨﺒﺎﺗﺎت اﻟﻤﺎﺋﯿﺔ ،واﻷﺳﻤﺎك واﻟﺮﺧﻮﯾﺎت ،ﺧﺎﺻﺔ اﻟﻘﻮاﻗﻊ اﻟﻨﺎﻗﻠﺔ ﻟﻤﺮض اﻟﺒﻠﮭﺎرﺳﯿﺎ وﻏﯿﺮھﺎ ،ﻣﻤﺎ ﯾﻌﺪ ﻣﺆﺷﺮاً إﯾﺠﺎﺑﯿﺎً ﻟﮭﺬا اﻟﺤﯿﻮان وإﻣﻜﺎﻧﯿﺔ اﺳﺘﺨﺪاﻣﮫ ﻓﻲ اﻟﻤﻜﺎﻓﺤﺔ اﻟﺒﯿﻮﻟﻮﺟﯿﺔ ﻟﻨﺎﻗﻼت ھﺬا اﻟﻤﺮض وﻏﯿﺮه ﻓﻲ اﻟﻘﻨﻮات اﻟﻤﺎﺋﯿﺔ اﻟﻤﺼﺎﺑﺔ ﺑﮭﺎ .وﻗﺪ أﺷﺎرت ﻧﺘﺎﺋﺞ اﻟﻤﺴﺢ اﻟﺤﻘﻠﻲ إﻟﻰ ﻧﻘﺺ ﻛﺒﯿﺮ أو اﺧﺘﻔﺎء ﻛﺎﻣﻞ ﻟﻠﻘﻮاﻗﻊ اﻟﻤﺬﻛﻮرة ﻣﻦ ھﺬه اﻟﻘﻨﻮات اﻟﺘﻲ دﺧﻠﺖ ﻓﯿﮭﺎ اﻻﺳﺘﺎﻛﻮزا ﺑﯿﻨﻤﺎ ﺳﺠﻠﺖ اﻟﻤﺠﺎري اﻟﻤﺎﺋﯿﺔ اﻟﺘﻲ ﻻ ﺗﺄوي ھﺬا اﻟﺤﯿﻮان ﻛﺜﺎﻓﺔ ﻋﺎﻟﯿﺔ ﻣﻦ ﺗﻠﻚ اﻟﻘﻮاﻗﻊ. ﻛﻤﺎ أن ﻣﺨﺰون ھﺬا اﻟﺤﯿﻮان ﻓﻲ ﻧﮭﺮ اﻟﻨﯿﻞ ﻣﺎزال دون اﻻﺳﺘﻐﻼل اﻷﻣﺜﻞ ،ﺣﯿﺚ ﯾﻤﻜﻦ اﻟﺤﺼﻮل ﻋﻠﻲ ئ ﻣﻦ اﻟﺴﻠﻚ ھﺮﻣﯿﺔ اﻟﺸﻜﻞ ﺗﻌﺮف ﺑﺎﻟﺠﻮﺑﯿﺎ اﻟﮭﺮﻣﯿﺔ ،ﻣﻤﺎ ﺣﻮاﻟﻲ 5ﻃﻦ ﻣﻨﮫ ﺳﻨﻮﯾﺎً ﻣﻦ ﺧﻼل ﻣﺼﺎ د ﯾﻀﯿﻒ ﻣﺼﺪراً ﺟﺪﯾﺪا ﻣﻦ ﻣﺼﺎدر اﻟﺒﺮوﺗﯿﻦ اﻟﺤﯿﻮاﻧﻲ اﻟﺮﺧﯿﺺ ﻓﻲ ﻣﺼﺮ. وﻟﻜﻦ ﻟﻸﺳﻒ ﻓﺈن وﺳﺎﺋﻞ اﻹﻋﻼم ﺗﻨﺎوﻟﺖ ھﺬا اﻟﻤﻮﺿﻮع ﺑﻄﺮﯾﻘﺔ ﺧﺎﻃﺌﺔ وﻏﯿﺮ ﻋﻠﻤﯿﺔ ،ﺣﯿﺚ ﺗﻢ ﺗﺴﻤﯿﺔ باﻟﺤﺸﺮة ھﺬا اﻟﺤﯿﻮان ﻣﺮة ﺑﺼﺮﺻﻮر اﻟﺒﺤﺮ اﻟﺬي ﯾﻐﺰو اﻟﻨﯿﻞ وﯾﻠﺘﮭﻢ اﻷﺳﻤﺎك دون رﺣﻤﺔ ،وﻣﺮة اﻟﺴﺎﻣﺔ اﻟﻘﺎدﻣﺔ ﻣﻦ إﺳﺮاﺋﯿﻞ وأﻣﺮﯾﻜﺎ ،واﻹﻋﻼن ﻋﻦ ﻗﯿﺎم وزارة اﻟﺘﻤﻮﯾﻦ ﺑﺤﺮق أﻃﻨﺎن ﻣﻦ ھﺬا اﻟﺤﯿﻮان ﻟﺨﻄﻮرﺗﮫ ﻋﻠﻰ ﺻﺤﺔ اﻟﻤﺴﺘﮭﻠﻜﯿﻦ دون وﻋﻰ ﺑﺄھﻤﯿﺘﮫ وﻓﻮاﺋﺪه اﻻﻗﺘﺼﺎدﯾﺔ. ﻟﺬﻟﻚ ﻛﺎن ﻻﺑﺪ ﻣﻦ إﻋﺪاد ﺑﺮﻧﺎﻣﺞ وﻃﻨﻲ ﯾﮭﺪف إﻟﻰ زﯾﺎدة اﻟﺘﻮﻋﯿﺔ ﺑﺄھﻤﯿﺔ ھﺬا اﻟﺤﯿﻮان اﻗﺘﺼﺎدﯾﺎ ﻛﻤﺼﺪر ﺟﺪﯾﺪ ورﺧﯿﺺ ﻟﻠﺒﺮوﺗﯿﻦ اﻟﺤﯿﻮاﻧﻲ ،وكوﺳﯿﻠﺔ ﻟﻠﻤﻜﺎﻓﺤﺔ اﻟﺒﯿﻮﻟﻮﺟﯿﺔ ﻟﻠﻘﻮاﻗﻊ اﻟﻨﺎﻗﻠﺔ ﻟﻸﻣﺮاض وﻛﻤﺼﺪر إﺿﺎﻓﻲ ﻓﻲ ﺻﻨﺎﻋﺔ ﻋﻼﺋﻖ اﻟﺪواﺟﻦ واﻷﺳﻤﺎك ،ﻛﻤﺎ ﯾﺘﻢ ﻓﻲ ﺑﻼد أﺧﺮى اﺳﺘﺨﺪام أﺣﺠﺎﻣﮫ اﻟﺼﻐﯿﺮة ﻛﻄﻌﻢ ﻟﺼﯿﺪ اﻷﺳﻤﺎك ،وﻓﻲ ﻣﺨﺘﻠﻒ اﻟﺪراﺳﺎت واﻟﺘﺠﺎرب اﻟﺒﯿﻮﻟﻮﺟﯿﺔ ﻧﻈﺮا ﻟﺘﻔﻮﻗﮫ ﻋﻠﻰ ﻏﯿﺮه ﻣﻦ ﺣﯿﻮاﻧﺎت اﻟﺘﺠﺎرب ﻓﻲ ﺗﺤﻤﻞ ﻇﺮوف اﻟﺒﯿﺌﺔ اﻟﻤﺨﺘﻠﻔﺔ.
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وﻟﺬﻟﻚ وﺿﻊ اﻟﺨﺒﺮاء اﻟﺬﯾﻦ ﺷﺎرﻛﻮا ﻓﻲ دراﺳﺎت ﻣﺴﺘﻔﯿﻀﺔ ﺣﻮل ذﻟﻚ اﻟﺤﯿﻮان اﻟﺪﺧﯿﻞ ﺑﺮﻧﺎﻣﺠﺎ ﺷﺎﻣﻼ لﻣﻮاﺟﮭﺔ ﺳﻠﺒﯿﺎﺗﮫ ﺧﺼﻮﺻﺎً ﺗﮭﺪﯾﺪه ﻷﻧﻈﻤﺔ اﻟﺮي ﻋﻠﻰ ﻃﻮل ﻣﺠﺮى ﻧﮭﺮ اﻟﻨﯿﻞ ،ﺗﺒﻨﺎه اﻟﺒﺮﻧﺎﻣﺞ ا ﻹﻧﻤﺎئي اﻟﺘﺎﺑﻊ ﻟﻸﻣﻢ اﻟﻤﺘﺤﺪة )ﻣﺸﺮوع اﻟﻤﻨﺢ اﻟﺼﻐﯿﺮة ( ﻋﺎم 2007ﻓﻰ ﻣﻘﺘﺮح ﺑﺤﺜﻰ ﺟﺪﯾﺪ .وﻛﺎﻧﺖ ﻣﻦ أھﻢ أھﺪاف ھﺬا اﻟﻤﺸﺮوع ﻣﺎ ﯾﻠﻲ: .١إﻋﺪاد ﻗﺎﻋﺪة ﺑﯿﺎﻧﺎت ﺗﺸﻤﻞ ﺟﻤﯿﻊ اﻟﻨﻮاﺣﻲ اﻟﺨﺎﺻﺔ ﺑﺎﻟﺪراﺳﺎت اﻟﺒﯿﺌﯿﺔ ﻟﮭﺬا اﻟﺤﯿﻮان داﺧﻞ ﻣﺼﺮ. .٢دراﺳﺔ ﻣﻌﺪل اﻧﺘﺸﺎر ھﺬا اﻟﺤﯿﻮان ﻓﻲ ﻣﯿﺎه اﻟﻨﯿﻞ ورواﻓﺪه ﻓﻲ اﻟﺴﻨﻮات اﻷﺧﯿﺮة اﺳﺘﻜﻤﺎﻻ ﻟﻠﺪراﺳﺎت اﻟﺴﺎﺑﻘﺔ . .٣دراﺳﺔ اﻟﺠﻮاﻧﺐ اﻟﺴﻠﺒﯿﺔ ﻟﮭﺬا اﻟﺤﯿﻮان ﻓﻲ اﻟﺒﯿﺌﺔ اﻟﻤﺼﺮﯾﺔ وﺗﻘﺪﯾﺮ ﻣﺪى اﻟﻀﺮر اﻟﺤﺎدث ﺑﺴﺒﺐ اﻧﺘﺸﺎره اﻟﻤﺘﺰاﯾﺪ واﻟﻌﺸﻮاﺋﻲ ﻓﻲ ﺷﺒﻜﺔ اﻟﺮي اﻟﻤﺼﺮﯾﺔ . .٤دراﺳﺔ اﻟﻘﯿﻤﺔ اﻟﻐﺬاﺋﯿﺔ ﻟﮭﺬا اﻟﺤﯿﻮان وﺗﻘﺪﯾﺮ اﻟﻤﻜﻮﻧﺎت اﻟﻐﺬاﺋﯿﺔ ﺑﮫ وﻣﻘﺎرﻧﺘﮭﺎ ﺑﺎﻷﻧﻮاع اﻟﻤﺨﺘﻠﻔﺔ ﻣﻦ اﻷﺳﻤﺎك واﻟﻘﺸﺮﯾﺎت اﻟﺘﻲ ﺗﺆﻛﻞ ﻓﻲ اﻟﺒﯿﺌﺔ اﻟﻤﺼﺮﯾﺔ. .٥ﺗﻘﺪﯾﺮ ﻣﺪى ﺗﺮﻛﯿﺰ اﻟﻌﻨﺎﺻﺮ اﻟﺜﻘﯿﻠﺔ واﻟﻤﻠﻮﺛﺎت اﻟﻀﺎرة ﻓﻲ ھﺬا اﻟﺤﯿﻮان وﺗﺮاﻛﻤﮭﺎ ﺑﺎﻟﻨﺴﺒﺔ ﻟﻠﺤﺠﻢ ﻓﻲ اﻟﻌﻀﻼت واﻟﮭﯿﻜﻞ اﻟﺨﺎرﺟﻲ وﺗﻮاﺟﺪ اﻟﻜﺎﺋﻨﺎت اﻟﺪﻗﯿﻘﺔ اﻟﻀﺎرة ﻣﻦ ﻋﺪﻣﮫ وذﻟﻚ ﻟﻺﺟﺎﺑﺔ ﻋﻠﻲ اﻟﺴﺆال اﻟﮭﺎم؛ ھﻞ ھﺬا اﻟﺤﯿﻮان ﺻﺎﻟﺢ ﻟﻶﻛﻞ ﻓﻲ اﻟﺒﯿﺌﺔ اﻟﻤﺼﺮﯾﺔ ﻛﻤﺎ ھﻮ ﻓﻲ ﻣﻮﻃﻨﮫ اﻷﺻﻠﻲ ؟ .٦ﻛﯿﻔﯿﺔ اﺳﺘﻐﻼل ھﺬا اﻟﻜﺎﺋﻦ ﻓﻲ اﻟﻤﻜﺎﻓﺤﺔ اﻟﺒﯿﻮﻟﻮﺟﯿﺔ ﻟﺒﻌﺾ اﻟﻘﻮاﻗﻊ اﻟﻨﺎﻗﻠﺔ ﻟﻤﺮض اﻟﺒﻠﮭﺎرﺳﯿﺎ واﻟﺪودة اﻟﻜﺒﺪﯾﺔ وﻏﯿﺮھﻤﺎ ﻓﻲ اﻟﻤﺠﺎري اﻟﻤﺎﺋﯿﺔ اﻟﻤﺼﺮﯾﺔ. .٧ﺳﺒﻞ اﻻﺳﺘﻔﺎدة ﻣﻦ اﻟﺨﺒﺮات اﻟﺴﺎﺑﻘﺔ ﻟﺘﺮﺑﯿﺔ واﺳﺘﺰراع ھﺬا اﻟﺤﯿﻮان ﻓﻲ ﺑﯿﺌﺘﮫ اﻷﺻﻠﯿﺔ ﻓﻲ وﻻﯾﺔ ﻟﻮﯾﺰﯾﺎﻧﺎ اﻷﻣﺮﯾﻜﯿﺔ ﻛﻨﻤﻮذج اﻣﺜﻞ ﻻﺳﺘﻐﻼل ھﺬا اﻟﺤﯿﻮان اﻟﺬي ﯾﻌﺘﺒﺮ ﻣﺼﺪرا ﻏﺬاﺋﯿﺎ ﻏﻨﯿﺎ ﺗﻘﻮم ﻋﻠﯿﮫ ﺻﻨﺎﻋﺔ واﺳﺘﺜﻤﺎرات واﺳﻌﺔ ھﻨﺎك. .٨ﻧﺸﺮ اﻟﻮﻋﻲ ﺑﯿﻦ اﻟﺼﯿﺎدﯾﻦ واﻟﻤﺰارﻋﯿﻦ واﻷھﺎﻟﻲ ﺑﺄھﻤﯿﺔ اﻻﺳﺘﻔﺎدة ﻣﻦ ھﺬا اﻟﺤﯿﻮان ﻛﻤﺼﺪر ﻟﻠﺒﺮوﺗﯿﻦ رﺧﯿﺺ اﻟﺜﻤﻦ . .٩ﺗﻮﺣﯿﺪ اﻟﺠﮭﻮد اﻟﻤﺒﺬوﻟﺔ ﻓﻲ ﻣﺨﺘﻠﻒ اﻟﺠﮭﺎت اﻟﺒﺤﺜﯿﺔ واﻟﻌﻠﻤﯿﺔ واﻟﺤﻜﻮﻣﯿﺔ اﻟﺘﻲ ﺗﺠﺮى ﺣﻮل دراﺳﺔ ھﺬا اﻟﺤﯿﻮان وﺳﺒﻞ اﻻﺳﺘﻔﺎدة ﻣﻦھﺎ. إﻗﺎﻣﺔ .١٠دراﺳﺔ إﻣﻜﺎﻧﯿﺔ اﺳﺘﻐﻼل اﻷراﺿﻲ اﻟﺒﻮر اﻟﻤﻮﺟﻮدة ﻓﻲ اﻟﺒﯿﺌﺔ اﻟﻤﺼﺮﯾﺔ ﻓﻲ ﻣﺰارع ﻟﻸﺳﺘﺎﻛﻮزا واﻟﺘﻲ ﺗﺘﻤﯿﺰ ﺑﻘﻠﺔ ﺗﻜﻠﻔﺘﮭﺎ وﻏﺰارة إﻧﺘﺎﺟﮭﺎ ﻣﻘﺎرﻧﮫ ﺑﺎﻷﻧﻮاع اﻷﺧﺮى ﻣﻦ اﻟﻤﺰارع اﻟﺴﻤﻜﯿﺔ. .١١إﺻﺪار اﻟﺘﺸﺮﯾﻌﺎت اﻟﻼزﻣﺔ ﻟﻠﺤﺪ ﻣﻦ إدﺧﺎل أي ﻛﺎﺋﻦ ﻏﺮﯾﺐ ﻋﻦ اﻟﺒﯿﺌﺔ اﻟﻤﺼﺮﯾﺔ دون دراﺳﺔ ﻣﺴﺘﻔﯿﻀﺔ ﻵﺛﺎره اﻟﻤﺘﻌﺪدة ﻓﻲ اﻟﺒﯿﺌﺔ اﻟﺠﺪﯾﺪة. اﻟﺘﻌﺎوﻧﻲ .١٢زﯾﺎدة ﻣﺸﺎرﻛﺔ اﻟﺠﮭﺎت اﻟﺘﻨﻔﯿﺬﯾﺔ ﻣﺜﻞ ھﯿﺌﺔ ﺗﻨﻤﯿﺔ اﻟﺜﺮوة اﻟﺴﻤﻜﯿﺔ واﻻﺗﺤﺎد ﻟﻠﺜﺮوة اﻟﻤﺎﺋﯿﺔ ﻣﻊ اﻟﺠﻤﻌﯿﺔ إﻟﻰ ﺟﺎﻧﺐ اﻟﺨﺒﺮاء واﻟﻤﮭﺘﻤﯿﻦ ﺑﺘﻨﻤﯿﺔ اﻟﺜﺮوة اﻟﺴﻤﻜﯿﺔ واﻟﺒﯿﺌﺔ
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اﻟﻤﺎﺋﯿﺔ ﺑﺎﻟﺠﺎﻣﻌﺎت واﻟﻤﺮاﻛﺰ اﻟﺒﺤﺜﯿﺔ ﻓﻲ ﻋﻘﺪ اﻟﻌﺪﯾﺪ ﻣﻦ اﻟﻨﺪوات وﺣﻤﻼت اﻟﺘﻮﻋﯿﺔ ﻟﻤﻮاﺟﮭﺔ ھﺬه اﻟﻤﺸﻜﻠﺔ. ) ﻛﻤﺎ أن ﻣﺸﺎرﻛﺔ اﻟﻘﺎﻋﺪة اﻟﺸﻌﺒﯿﺔ اﻟﻤﺘﻤﺜﻠﺔ ﻓﻲ اﻟﻔﺌﺎت اﻟﻤﺘﻀﺮرة ﻣﻦ وﺟﻮد ھﺬا اﻟﺤﯿﻮان اﻟﺼﯿﺎدﯾﻦ واﻟﻤﺰارﻋﯿﻦ ( ﻓﻲ ﺗﻨﻔﯿﺬ ﺗﻮﺻﯿﺎت ھﺬا اﻟﻤﺸﺮوع وﺣﻤﻼت اﻟﺘﻮﻋﯿﺔ ،ﻗﺪ ﺳﺎھﻢ إﻟﻲ ﺣﺪ ﻛﺒﯿﺮ ﻓﻲ ﺑﺤﺚ اﻟﺤﻠﻮل ودراﺳﺔ ﺳﺒﻞ ﺗﻄﺒﯿﻘﮭﺎ وﺗﺼﻤﯿﻢ ﺣﻤﻼت اﻟﺘﻮﻋﯿﺔ اﻟﻼزﻣﺔ ﻟﻠﻤﺴﺘﻔﯿﺪﯾﻦ ﻣﻦ ھﺬا اﻟﻤﺸﺮوع وإﻧﺸﺎء ﻗﺎﻋﺪة ﺑﯿﺎﻧﺎت ﻛﺎﻣﻠﺔ ﺗﺘﯿﺢ ﻟﻠﻤﺴﺌﻮﻟﯿﻦ وﺻﺎﻧﻌﻲ اﻟﻘﺮار اﻹﺟﺎﺑﺔ ﻋﻠﻰ ﻛﺜﯿﺮ ﻣﻦ اﻟﺘﺴﺎؤﻻت اﻟﻤﻄﺮوﺣﺔ ﺣﻮل اﻧﺘﺸﺎر ھﺬا اﻟﺤﯿﻮان اﻟﺪﺧﯿﻞ ﻓﻲ اﻟﺒﯿﺌﺔ اﻟﻤﺎﺋﯿﺔ اﻟﻤﺼﺮﯾﺔ. وﻗﺪ ﺗﺒﯿﻦ ﺑﻌﺪ ﺳﻨﻮات ﻣﻦ اﻟﺪراﺳﺎت واﻟﺒﺤﻮث اﻟﺘﻲ أﺟﺮﯾﺖ ﻋﻠﻰ ھﺬا اﻟﺤﯿﻮان ﺿﺮورة وﺟﻮد ﻣﺮﺟﻊ ﻣﻮﺛﻖ ﯾﺠﻤﻊ ﻧﺘﺎﺋﺞ ھﺬه اﻟﺪراﺳﺎت ،ﺣﻮل ﻣﺪى ﺗﻮزﯾﻌﮫ اﻟﺠﻐﺮاﻓﻲ ﻓﻲ ﻣﺼﺮ....و ﻃﺮق ﺗﻐﺬﯾﺘﮫ ،وﺗﻜﺎﺛﺮه وﻧﻤﻮه وإﻣﻜﺎﻧﯿﺔ اﺳﺘﺰراﻋﮫ وﻣﻼءﻣﺘﮫ اﻟﻔﺴﯿﻮﻟﻮﺟﯿﺔ وﺳﻠﻮﻛﮫ ﻓﻲ ﺑﯿﺌﺘﮫ اﻟﺠﺪﯾﺪة...وﻋﻦ اﻹﺳﺘﺮاﺗﯿﺠﯿﺔ اﻟﻌﻠﻤﯿﺔ اﻟﺘﻲ ﯾﺠﺐ أن ﻧﺘﺒﻌﮭﺎ ﺣﺘﻰ ﻧﺴﺘﻄﯿﻊ اﻻﺳﺘﻔﺎدة اﻟﻘﺼﻮى ﻣﻨﮫ ھﺬه واﻟﺤﺪ ﻣﻦ ﺳﻠﺒﯿﺎﺗﮫ ﻋﻠﻰ ﺑﯿﺌﺔ ﻧﮭﺮ اﻟﻨﯿﻞ وھﺎ ﻧﺤﻦ ﻧﻘﺪم ﻓﻲ ھﺬا اﻟﻜﺘﺎب ﻣﻮﺟﺰا ﻷھﻢ ﻧﺘﺎﺋﺞ اﻟﺪراﺳﺎت وذﻟﻚ ﻛﻤﺎ ﯾﻠﻲ: اﻟﺸﻜﻞ اﻟﺨﺎرﺟﻲ واﻟﺘﺸﺮﯾﺢ اﻟﺪاﺧﻠﻲ: ﯾﺘﻜﻮن ﺟﺴﻢ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻣﻦ ﻋﺸﺮﯾﻦ ﻋﻘﻠﺔ ،وﺗﻠﺘﺤﻢ اﻷرﺑﻊ ﻋﺸﺮة ﻋﻘﻠﺔ اﻷ ﻣﺎﻣﯿﺔ ﻣﻜﻮﻧﺔ رأﺳﺼﺪر ) (cephalothoraxﯾﻤﺜﻞ اﻟﺮأس واﻟﺼﺪر ،اﻟﻠﺬان ﯾﻠﺘﺤﻤﺎ ﻇﮭﺮﯾﺎ وﺟﺎﻧﺒﯿﺎ ،وﻟﻜﻦ ﻻ ﯾﺰال اﻟﺘﻘﺴﯿﻢ واﺿﺤﺎ ﻋﻠﻰ اﻟﺴﻄﺢ اﻟﺒﻄﻨﻲ .وﯾﺘﺮﻛﺐ اﻟﺒﻄﻦ ﻣﻦ ﺳﺖ ﺣﻠﻘﺎت واﺿﺤﺔ ﯾﻤﻜﻦ ﻣﻼﺣﻈﺘﮭﺎ ﺑﺴﮭﻮﻟﺔ ﻣﻦ اﻟﺨﺎرج. اﺟﺰ اء اﻟﺠﺴﻢ ﻣﻜﻮﻧﺎ ھﯿﻜﻼ واﻟﺠﻠﯿﺪ اﻟﺬي ﺗﻔﺮزه اﻟﺒﺸﺮة اﻟﺘﻲ ﺗﺤﺘﮫ ،ﯾﻐﻄﻰ ﻛﻞ ﺧﺎرﺟﯿﺎ ) (exoskeletonﯾﺘﺼﻠﺐ ﺑﺸﻜﻞ ﺧﺎص ﻧﺘﯿﺠﺔ ﺗﺪﻋﯿﻤﮫ ﺑﺄﻣﻼح اﻟﺠﯿﺮ .وﯾﻘﺪم اﻟﺠﻠﯿﺪ ﻧﻮﻋﺎ ﻣﻦ اﻟﺪﻋﺎﻣﺔ اﻟﺨﺎرﺟﯿﺔ ﻟﻠﺠﺴﻢ ﺑﻮﺳﺎﻃﺔ أﻟﻮاح رﻗﯿﻘﺔ ﻣﻦ اﻟﻜﯿﺘﯿﻦ ﺗﻔﺮزھﺎ ﻃﯿﺎت داﺧﻠﯿﺔ ﻣﻦ اﻟﺒﺸﺮة، وﺗﺰﯾﺪ ھﺬه اﻷﻟﻮاح ﻣﺴﺎﺣﺔ ﺳﻄﺢ اﻟﺘﺼﺎق اﻟﻌﻀﻼت ،وﺗﺤﻤﻲ أﻋﻀﺎء ھﺎﻣﺔ .وﯾﻜﻮن اﻟﺠﻠﯿﺪ اﻟﻤﺘﺼﻠﺐ ﻋﻠﻰ ﺳﻄﺢ اﻟﺮأﺳﺼﺪر وﺟﺎﻧﺒﯿﮫ درﻋﺎ واﻗﯿﺎ ﻛﺒﯿﺮا – ﯾﻌﺮف ﺑﺎﻟﺪرﻗﺔ ). (carapace واﻟﺠﻠﯿﺪ ﻓﻲ ﻣﻨﻄﻘﺔ اﻟﺒﻄﻦ رﻗﯿﻖ ﺑﯿﻦ اﻟﺤﻠﻘﺎت وﺑﺬا ﯾﺴﻤﺢ ﺑﺎﻧﺜﻨﺎء اﻟﺠﺴﻢ .وأﻗﻞ اﻟﺰواﺋﺪ ﺗﺤﻮرا ھﻲ زواﺋﺪ اﻟﺒﻄﻦ ،وﺗﺘﺮﻛﺐ ﻛﻞ ﻣﻨﮭﺎ ﻣﻦ ﻗﻄﻌﺔ أوﻟﯿﺔ ) (protopoditeﺗﺤﻤﻞ ﻋﻨﺪ ﻧﮭﺎﯾﺘﮭﺎ اﻟﻄﻠﯿﻘﺔ ﻓﺮﻋﺎ ﺧﺎرﺟﯿﺎ ) (exopoditeوﻓﺮﻋﺎ داﺧﻠﯿﺎ ). (endopodite وﯾﺘﺮﻛﺐ اﻟﺮأس ﻛﻤﺎ ﻓﻲ ﻛﻞ اﻟﻘﺸﺮﯾﺎت ﻣﻦ ﺳﺖ ﻋﻘﻼت ،اﻷوﻟﻰ ﻣﻨﮭﺎ ﺗﺤﻤﻞ زوﺟﺎ ﻣﻦ اﻟﻌﯿﻮن اﻟﻤﺮﻛﺒﺔ ﻣﺤﻤﻮﻟﺔ ﻛﻞ ﻣﻨﮭﺎ ﻋﻠﻰ ﺳﺎق ﻣﺘﻤﻔﺼﻠﺔ وﻗﺎﺑﻠﺔ ﻟﻠﺤﺮﻛﺔ .وﯾﻮﺟﺪ ﻋﻠﻰ اﻟﻌﻘﻠﺔ اﻟﺜﺎﻧﯿﺔ ﻗﺮﻧﺎ ﻟﻼﺳﺘﺸﻌﺎر اﻷوﻻن وھﻤﺎ ﺗﺮﻛﯿﺒﺎن ﺣﺴﯿﺎن ﻟﻜﻞ ﻣﻨﮭﻤﺎ ﺳﻮﻃﺎن .وﻗﺮﻧﺎ اﻻﺳﺘﺸﻌﺎر اﻟﺜﺎﻧﯿﺎن ﻣﻮﺟﻮدان ﻋﻠﻰ اﻟﻌﻘﻠﺔ اﻟﺜﺎﻟﺜﺔ ،وﻟﮭﻤﺎ ﻓﺮع واﺣﺪ ﻓﻘﻂ ﻃﻮﯾﻞ ،ﯾﺘﺸﺎﺑﮫ ﺗﺮﻛﯿﺒﯿﺎ ﻣﻊ اﻟﻔﺮع اﻟﺪاﺧﻠﻲ ﻟﻠﺰواﺋﺪ اﻷﺧﺮى ،واﻟﻔﺮ ع اﻟﺨﺎرﺟﻲ ﯾﺸﺒﮫ اﻟﺤﺮﺷﻔﺔ .وﺗﺤﻤﻞ اﻟﻌﻘﻠﺔ اﻟﺮاﺑﻌﺔ ﻣﻦ اﻟﺮأس زوﺟﺎ ﻣﻦ ﻓﻜﻮك ذات أﺳﻨﺎن ﻟﺴﺤﻖ اﻟﻄﻌﺎم وﻋﻠﻰ اﻟﺤﻠﻘﺘﯿﻦ اﻟﺨﺎﻣﺴﺔ واﻟﺴﺎدﺳﺔ ﯾﻮﺟﺪ اﻟﻔﻜﺎن اﻟﻤﺴﺎﻋﺪان 157
اﻷول واﻟﺜﺎﻧﻲ ) (first and second maxillaeاﻟﻠﺬان ﯾﺪﻓﻌﺎن اﻟﻄﻌﺎم ﻟﻠﻔﻢ .واﻟﻔﻚ اﻟﻤﺴﺎﻋﺪ اﻟﺜﺎﻧﻲ ﻋﺒﺎرة ﻋﻦ ﻟﻮح رﻗﯿﻖ ذي ﻓﺼﻮص ،وﻋﻤﻠﮫ اﻟﺮﺋﯿﺴﻲ ﺗﻨﻔﺴﻲ إذ ﯾﺘﺤﺮك إﻟﻰ اﻷﻣﺎم واﻟﺨﻠﻒ ﺑﺎﺳﺘﻤﺮار ﻓﯿﻮﻟﺪ ﺗﯿﺎرا ﯾﺠﺪد اﻟﻤﺎء ﻧﺤﻮ اﻟﺘﺠﻮﯾﻒ اﻟﺘﻨﻔﺴﻲ. وﻓﻲ ﻋﻘﻼت اﻟﺼﺪر اﻟﺜﻤﺎﻧﯿﺔ ﯾﻮﺟﺪ زوج ﻣﻦ اﻟﺰواﺋﺪ ﻋﻠﻰ ﻛﻞ ﻋﻘﻠﺔ .وﺗﺤﻤﻞ اﻟﻌﻘﻼت اﻟﺜﻼﺛﺔ اﻷوﻟﻰ اﻷرﺟﻞ اﻟﻔﻜﯿﺔ ) (maxillipedsاﻷوﻟﻰ واﻟﺜﺎﻧﯿﺔ واﻟﺜﺎﻟﺜﺔ ،وھﻰ زواﺋﺪ ﺣﺴﯿﺔ ﻟﺤﺪ ﻣﺎ، وﻟﻜﻦ ﻋﻤﻠﮭﺎ اﻟﺮﺋﯿﺴﻲ ھﻮ ﻣﻌﺎﻟﺠﺔ اﻟﻄﻌﺎم ﻓﺘﻄﺤﻨﮫ أوﻻ ﺛﻢ ﺗﻤﺮره إﻟﻰ اﻟﻔﻢ .واﻟﺮﺟﻞ اﻟﻔﻜﯿﺔ اﻟﺜﺎﻟﺜﺔ ھﻰ اﻟﻮﺣﯿﺪة اﻟﺘﻲ ﺗﻘﻮى ﻋﻠﻰ اﻟﻘﯿﺎم ﺑﻤﻀﻎ ﺣﻘﯿﻘﻲ إﻻ إذا ﻛﺎن اﻟﻄﻌﺎم رﺧﻮا .وﺗﺤﻤﻞ اﻟﻘﻄﻌﺔ اﻟﻘﺎﻋﺪﯾﺔ ﻓﻲ ﻛﻞ رﺟﻞ ﻓﻜﯿﺔ ورﯾﻘﺔ زاﺋﺪﯾﺔ ) (epipoditeﯾﺘﺼﻞ ﺑﮭﺎ ﺧﯿﺸﻮم ﻓﻲ ﻛﻞ ﻣﻦ اﻟﺮﺟﻞ اﻟﻔﻜﯿﺔ اﻟﺜﺎﻧﯿﺔ واﻟﺜﺎﻟﺜﺔ .وﺗﻌﻤﻞ ھﺬه اﻟﻮرﯾﻘﺎت ﻋﻠﻰ ﻓﺼﻞ اﻟﺨﯿﺎﺷﯿﻢ ﻋﻦ ﺑﻌﻀﮭﺎ وﺣﻤﺎﯾﺘﮭﺎ .وﺗﺤﻤﻞ اﻟﻌﻘﻠﺔ اﻟﺼﺪرﯾﺔ اﻟﺮاﺑﻌﺔ اﻟﻤﺨﺎﻟﺐ اﻟﻘﻮﯾﺔ أو اﻟﻜﻼﺑﺎت اﻟﻘﺎ بﺿﺔ ) (chelipedsوھﻲ ﺗﺴﺘﻌﻤﻞ ﻓﻲ ).(walking legs اﻟﺪﻓﺎع واﻟﮭﺠﻮم .وﻟﻜﻞ ﻣﻦ اﻷرﺑﻊ ﺣﻠﻘﺎت اﻟﺘﺎﻟﯿﺔ زوج ﻣﻦ زواﺋﺪ اﻟﻤﺸﻲ وﺗﮭﺰ زواﺋﺪ اﻟﻤﺸﻲ اﻟﺨﯿﺎﺷﯿﻢ ﻓﻲ أﺛﻨﺎء ﺳﯿﺮ اﻟﺤﯿﻮان ،ﺣﺘﻰ ﺗﺤﺮك اﻟﻤﺎء ﻓﻲ اﻟﺘﺠﻮﯾﻒ اﻟﺨﯿﺸﻮﻣﻲ ﺗﺤﺖ اﻟﺪرﻗﺔ. وﺗﺤﻤﻞ ﻛﻞ ﻋﻘﻠﺔ ﻣﻦ ﻋﻘﻞ اﻟﺒﻄﻦ ﻋﺪا اﻟﻌﻘﻠﺔ اﻷﺧﯿﺮة زوﺟﺎ ﻣﻦ اﻟﺰواﺋﺪ ،واﻟﺰوج اﻷول ﻣﺨﺘﻠﻒ ﻓﻲ اﻟﺠﻨﺴﯿﻦ ،ﻓﻔﻲ اﻟﺬﻛﺮ ﯾﺘﺤﻮر ﻣﻜﻮﻧﺎ ﺗﺮﻛﯿﺒﺎ ﯾﺸﺒﮫ اﻟﻘﻨﺎة ﯾﺴﺘﻌﻤﻞ ﻓﻲ ﻧﻘﻞ اﻟﺤﯿﻮاﻧﺎت اﻟﻤﻨﻮﯾﺔ ﻓﻲ أﺛﻨﺎء ﻋﻤﻠﯿﺔ اﻟﺴﻔﺎد ،وﻓﻲ اﻷﻧﺜﻰ ﯾﻜﻮن ﻣﺨﺘﺰﻻ وﺗﺤﻤﻞ اﻟﺤﻠﻘﺎت اﻷرﺑﻊ اﻟﺘﺎﻟﯿﺔ زواﺋﺪ ﻣﺘﺸﺎﺑﮭﺔ ذات ﻓﺮﻋﯿﻦ ھﻰ زواﺋﺪ اﻟﺴﺒﺎﺣﺔ ) ، (swimmeretsوﺗﺴﺘﻌﻤﻞ ﻓﻲ اﻟﺴﺒﺎﺣﺔ إﻟﻰ اﻷﻣﺎم ﻛﻤﺎ ﺗﺴﺘﻌﻤﻞ ؛ اﻟﺰواﺋﺪ ﻓﻲ اﻷﻧﺜﻰ ﻛﻤﻮﺿﻊ ﻻﻟﺘﺼﺎق اﻟﺒﯿﺾ ﺑﻌﺪ وﺿﻌﮫ .أﻣﺎ زواﺋﺪ اﻟﺤﻠﻘﺔ اﻟﺒﻄﻨﯿﺔ اﻟﺴﺎدﺳﺔ اﻟﺬﯾﻠﯿﺔ ) (uropodsﻓﮭﻲ ﺗﺸﺒﮫ زواﺋﺪ ﻋﻮم ﻣﺘﻀﺨﻤﺔ ﻣﺘﺤﻮرة ،ﺗﺴﺘﻌﻤﻞ ﻓﻲ اﻟﺴﺒﺎﺣﺔ إﻟﻰ اﻟﺨﻠﻒ. ) اﻟﺠﺰء وﻣﻦ أھﻢ أﺟﺰاء ﺟﺴﻢ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ اﻟﺪاﺧﻠﯿﺔ ھﻲ اﻟﻌﻀﻼت اﻟﺒﻄﻨﯿﺔ اﻟﻜﺒﯿﺮة اﻟﺬي ﻧﺄﻛﻠﮫ ﻣﻦ اﻟﺤﯿﻮان( ،وھﻲ ﻣﺮﺗﺒﺔ ﺗﺮﺗﯿﺒﺎ ﻋﻘﻠﯿﺎ ،وﺗﺸﻤﻞ ﻋﻀﻼت ﻟﺘﺤﺮﯾﻚ زواﺋﺪ اﻟﻌﻮم، وﻋﻀﻼت ﺑﺎﺳﻄﺔ ﻟﻔﺮد اﻟﺒﻄﻦ ،وﻋﻀﻼت ﻣﺜﻨﯿﺔ أﻛﺒﺮ ﺑﻜﺜﯿﺮ ،وھﻲ اﻟﻤﺼﺪر اﻟﺮﺋﯿﺴﻲ ﻟﻠﻘﻮة اﻟﻼزﻣﺔ ﻟﻠﺤﺮﻛﺔ .وﻓﻲ اﻟﺤﺮﻛﺔ اﻟﺴﺮﯾﻌﺔ ﯾﺜﻨﻰ اﻻﺳﺘﺎﻛﻮزا ﺑﻄﻨﮫ إﻟﻰ أﺳﻔﻞ ﺑﻘﻮة ﺷﺪﯾﺪة ﻟﺪرﺟﺔ أن اﻟﺤﯿﻮان ﻛﻠﮫ ﯾﻨﺪﻓﻊ ﻟﻠﺨﻠﻒ ﻓﻲ اﻟﻤﺎء .وﻓﻲ اﻟﺮأﺳﺼﺪر ﺗﻮﺟﺪ ﻋﻀﻼت ﻋﺪﯾﺪة ﻟﺘﺤﺮﯾﻚ اﻟﺰواﺋﺪ وأﻋﻀﺎء أﺧﺮى. وﯾﺘﺮﻛﺐ ﺟﮭﺎز اﻟﮭﻀﻢ ﻓﻲ اﻻﺳﺘﺎﻛﻮزا ﻣﻦ ﺛﻼﺛﺔ أﺟﺰاء وﺗﻀﻢ اﻟﻤﻊى اﻷﻣﺎﻣﻲ ﻓﺎﻟﻤﺘﻮﺳﻂ ﺛﻢ اﻟﻤﻊى اﻟﺨﻠﻔﻲ إلى ﺟﺎﻧﺐ اﻟﻐﺪة اﻟﮭﺎﺿﻤﺔ .وﺗﺘﻜﻮن ﻛﻞ ﻣﻦ اﻟﻤﻊ ى اﻷﻣﺎﻣﻲ واﻟﺨﻠﻔﻲ ﻛﻨﻤﻮ داﺧﻠﻲ أﻧﺒﻮﺑﻲ ﻣﻦ ﻃﻼﺋﯿﺔ اﻻﻛﺘﻮدرم ،وﺑﺬا ﻓﮭﻤﺎ ﻣﺒﻄﻨﺘﺎن ﺑﺠﻠﯿﺪ ﻣﺘﺼﻞ ﺑﺎﻟﮭﯿﻜﻞ اﻟﺨﺎرﺟﻲ ﯾﻨﺰﻋﮫ اﻟﺤﯿﻮان ﻋﻨﺪ اﻧﺴﻼﺧﮫ ،أﻣﺎ اﻟﻤﻌﻰ اﻟﻤﺘﻮﺳﻂ ﻓﻘﺼﯿﺮ وﻏﯿﺮ ﻣﻐﻄﻰ ﺑﺠﻠﯿﺪ وﯾﺘﺼﻞ ﺑﺎﻟﻐﺪة اﻟﮭﺎﺿﻤﺔ اﻟﻜﺒﯿﺮة واﻟﺘﻲ ﺗﻘﻮم ﺑﺎﻟﮭﻀﻢ واﻻﻣﺘﺼﺎص .وﯾﺘﻤﺰق اﻟﻄﻌﺎم إﻟﻰ ﻗﻄﻊ ﺻﻐﯿﺮة ﺑﻮﺳﺎﻃﺔ اﻷرﺟﻞ اﻟﻔﻜﯿﺔ واﻟﻔﻜﻮك اﻟﻤﺴﺎﻋﺪة ،ﺛﻢ ﺗﺤﻄﻤﮫ اﻟﻔﻜﻮك ﻗﺒﻞ أن ﯾﺪﺧﻞ اﻟﻔﻢ وﻛﻤﺎ ﻟﻮ أن ذﻟﻚ ﻏﯿﺮ ﻛﺎف ﻓﺈن ﺟﺰءا ﻣﻦ اﻟﻤﻌﺪة ﻣﺘﺨﺼﺺ ﻛﻘﺎﻧﺼﺔ ﻣﺒﻄﻨﺔ ﺑﺄﺳﻨﺎن ﻛﯿﺘﯿﻨﯿﺔ ﺻﻠﺒﺔ ﺗﺤﺮﻛﮭﺎ ﻣﺠﻤﻮﻋﺎت ﻋﺪة ﻣﻦ اﻟﻌﻀﻼت وﻓﻲ اﻟﻤﻌﺪة ﯾﺘﺤﻮل اﻟﻄﻌﺎم إﻟﻰ ﻓﺘﺎت دﻗﯿﻖ ﺛﻢ ﯾﺼﻔﻰ وﯾﺨﺘﺰن .وﺗﻤﺮ أﺻﻐﺮ اﻟﺠﺰﯾﺌﺎت ﻓﻲ ﺗﯿﺎر ﺳﺎﺋﻞ 158
إﻟﻰ ﻏﺪة اﻟﮭﻀﻢ اﻟﻜﺒﯿﺮة ﺣﯿﺚ ﯾﺘﻢ ھﻀﻤﮭﺎ واﺧﺘﺰاﻧﮭﺎ وﺗﻤﺮ اﻟﺠﺰﯾﺌﺎت اﻷﻛﺒﺮ ﻓﻲ ﺗﯿﺎر ﻣﺴﺘﻤﺮ إﻟﻰ اﻷﻣﻌﺎء ﻟﯿﻌﺎد ھﻀﻤﮭﺎ. واﻟﺴﻄﺢ اﻟﺘﻨﻔﺴﻲ اﻟﻤﺘﺴﻊ اﻟﺬي ﯾﺤﺘﺎﺟﮫ ﺣﯿﻮان ﻗﺸﺮى ﻛﺒﯿﺮ وﻧﺸﻂ ﻛﺎﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﯾﻮﻓﺮه ﻋﺸﺮون زوﺟﺎ ﻣﻦ اﻟﺨﯿﺎﺷﯿﻢ وھﻲ اﻣﺘﺪادات رﯾﺸﯿﺔ ﻣﻦ ﺟﺪار اﻟﺠﺴﻢ ﻣﻤﻠﻮءة ﺑﻘﻨﻮات ﺗﺤﻤﻞ اﻟﺪم. واﻟﺨﯿﺎﺷﯿﻢ ﻣﺘﺼﻠﺔ ﺑﻘﻮاﻋﺪ اﻟﺰواﺋﺪ وﺑﺎﻷﻏﺸﯿﺔ ﺑﯿﻦ اﻟﺰواﺋﺪ وﺑﺠﺪار اﻟﺼﺪر .وﺗﻮﺟﺪ ﻋﻠﻰ ﺟﺎﻧﺒﻲ اﻟﺠﺴﻢ ﻓﻲ ﺗﺠﻮﯾﻒ ﯾﻐﻄﯿﮫ ﺟﺎﻧﺐ اﻟﺪر ﻗﺔ وﯾﺪﺧﻞ اﻟﻤﺎء إﻟﻰ اﻟﺘﺠﻮﯾﻒ ﻋﻨﺪ ﻃﺮف اﻟﺪر ﻗﺔ اﻟﻄﻠﯿﻘﺔ، وﯾﻤﺮ إﻟﻰ أﻋﻠﻰ وإﻟﻰ اﻷﻣﺎم ﻋﻠﻰ اﻟﺨﯿﺎﺷﯿﻢ ،وﯾﻤﺮ إﻟﻰ اﻟﺨﺎرج ﻓﻲ ﺗﯿﺎر ﯾﺤﺪﺛﮫ اﻟﻔﺮع اﻟﺨﺎرﺟﻲ اﻟﻤﻨﺒﺴﻂ ﻟﻠﻔﻚ اﻟﻤﺴﺎﻋﺪ اﻟﺜﺎﻧﻲ. واﻟﺠﮭﺎز اﻟﺪوري ﺟﮭﺎز ﻣﻔﺘﻮح واﻟﻘﻠﺐ ﻋﻀﻠﻲ وﯾﻮﺟﺪ ﻇﮭﺮﯾﺎ ﻓﻲ ﺗﺠﻮﯾﻒ ﻣﻤﻠﻮء ﺑﺎﻟﺪم وھﻮ ﺳﺎﺋﻞ ﺷﻔﺎف ﯾﺤﻤﻞ ﺻﺒﻐﺔ ھﯿﻤﻮﺳﯿﺎﻧﯿﻦ ،وﯾﻮﺟﺪ ﻓﻲ ﺟﻮاﻧﺐ اﻟﻘﻠﺐ ﺛﻼﺛﺔ أزواج ﻣﻦ الﻓﺘﺤﺎت ﯾﻤﺮ ﺧﻼﻟﮭﺎ اﻟﺪم ﻣﻦ اﻟﺘﺠﻮﯾﻒ إﻟﻰ اﻟﻘﻠﺐ ﻓﻲ أﺛﻨﺎء ارﺗﺨﺎﺋﮫ ،وﻋﻨﺪﻣﺎ ﯾﺘﻖ ﺑﺾ اﻟﻘﻠﺐ ﻻ ﯾﺮﺗﺪ اﻟﺪم إﻟﻰ اﻟﻔﺘﺤﺎت ﻟﻮﺟﻮد ﺻﻤﺎﻣﺎت ﺗﻤﻨﻊ ذﻟﻚ ،وﻟﻜﻨﮫ ﯾﺪﻓﻊ ﻓﻲ ﺷﺮاﯾﯿﻦ ﺗﻤﺪ أﻧﺴﺠﺔ اﻟﺠﺴﻢ .وﻻ ﺗﻔﺘﺢ اﻟﻔﺮوع اﻟﺼﻐﯿﺮة ﻟﻠﺸﺮاﯾﯿﻦ إﻟﻰ أوردة وﻟﻜﻦ إﻟﻰ ﺗﺠﺎوﯾﻒ اﻟﺪم ﺑﯿﻦ اﻷﻧﺴﺠﺔ واﻟﺘﻲ ﺗﺴﻤﻰ ﺟﯿﻮب دﻣﻮﯾﺔ .وﯾﺘﺠﻤﻊ اﻟﺪم اﻟﻌﺎﺋﺪ ﻣﻦ اﻷﻧﺴﺠﺔ ﻓﻲ ﺟﯿﺐ ﺑﻄﻨﻲ ﻛﺒﯿﺮ ،وﻣﻦ ھﻨﺎك ﯾﺪﺧﻞ اﻟﻰ اﻟﺨﯿﺎﺷﯿﻢ ﺣﯿﺚ ﯾﺘﺨﻠﺺ ﻣﻦ ﺛﺎﻧﻲ أﻛﺴﯿﺪ اﻟﻜﺮﺑﻮن وﯾﺄﺧﺬ اﻷﻛﺴﺠﯿﻦ ،ﺛﻢ ﯾﻌﻮد ﻋﻦ ﻃﺮﯾﻖ ﻋﺪد ﻣﻦ اﻷوردة إﻟﻰ اﻟﺠﯿﺐ اﻟﺘﺎﻣﻮري اﻟﻤﺤﯿﻂ ﺑﺎﻟﻘﻠﺐ. وﺗﺘﻜﻮن أﻋﻀﺎء اﻹﺧﺮاج ﻣﻦ زوج ﻣﻦ اﻟﻐﺪد ﺗﺴﻤﻰ اﻟﻐﺪد اﻟﺨﻀﺮاء ﺑﺴﺒﺐ ﻟﻮﻧﮭﺎ اﻷﺧﻀﺮ أو اﻟﻐﺪد اﻟﺰﺑﺎﻧﯿﺔ ﻟﻮﺟﻮدھﺎ ﻓﻲ ﻗﺎﻋﺪة اﻟﺰﺑﺎن أوﻗﺮن اﻻﺳﺘﺸﻌﺎر اﻟﺜﺎﻧﻲ .وﺗﺘﻜﻮن ﻛﻞ ﻏﺪة ﻣﻦ ﻛﯿﺲ ﻏﺪي وأﻧﺒﻮﺑﺔ ﻣﻠﺘﻔﺔ ﺗﻔﺘﺢ ﻓﻲ ﻣﺜﺎﻧﺔ ﻋﻀﻠﯿﺔ .وﺗﺴﺘﺨﻠﺺ ﻓﻀﻼت ھﺪم اﻟﻄﻌﺎم ﻣﻦ اﻟﺪم وﺗﻤﺮ إﻟﻰ اﻟﻤﺜﺎﻧﺔ وﻣﻦ ھﻨﺎك إﻟﻰ اﻟﺨﺎرج ﺧﻼل ﺛﻘﺐ ﻋﻨﺪ ﻗﺎﻋﺪة ﻗﺮن اﻻﺳﺘﺸﻌﺎر اﻟﺜﺎﻧﻲ. واﻟﻄﺮاز اﻟﻌﺎم ﻟﻠﺠﮭﺎز اﻟﻌﺼﺒﻲ ﻓﻰ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﯾﺸﺒﮫ ذﻟﻚ اﻟﻤﻮﺟﻮد ﻓﻲ اﻟﻘﺸﺮﯾﺎت اﻟﻜﺒﯿﺮة ﺣﯿﺚ ﺗﻮﺟﺪ ﻋﻘﺪة ﻣﺨﯿﺔ ﻣﺰدوﺟﺔ ﻓﻲ اﻟﺮأس ﻗﺮب اﻟﻌﯿﻨﯿﻦ ﺗﻤﺘﺪ ﻣﻨﮭﺎ وﺻﻠﺘﺎن إﻟﻰ اﻟﺴﻄﺢ اﻟﺒﻄﻨﻲ؛ وﺻﻠﺔ ﻋﻠﻰ ﻛﻞ ﺟﺎﻧﺐ ﻟﻠﻤﺮيء ،ﺗﺘﺤﺪان ﺗﺤﺖ اﻟﻤﺮيء وﺗﻜﻮﻧﺎن ﻋﻘﺪة ﻣﺰدوﺟﺔ ھﻲ اﻟﻌﻘﺪة اﻟﺒﻄﻨﯿﺔ اﻷوﻟﻰ اﻟﺘﻲ ﯾﻤﺘﺪ ﻣﻨﮭﺎ إﻟﻰ اﻟﺨﻠﻒ اﻟﺤﺒﻞ اﻟﻌﺼﺒﻲ اﻟﻤﺰدوج اﻟﺬي ﯾﻨﺘﻔﺦ ﻣﻜﻮﻧﺎ ﻋﻘﺪا ﻣﺰدوﺟﺔ ﻓﻲ ﻛﻞ ﺣﻠﻘﺔ ﻣﻦ ﺣﻠﻘﺎت اﻟﺠﺴﻢ .وأﻛﺒﺮ أﻋﻀﺎء اﻟﺤﺲ ﻇﮭﻮرا ھﻲ ﻗﺮون اﻻﺳﺘﺸﻌﺎر واﻟﻌﯿﻮن اﻟﻤﺮﻛﺒﺔ ﺑﺎﻹﺿﺎﻓﺔ إﻟﻰ ﺷﻌﯿﺮات ﺣﺴﺎﺳﺔ ﻣﻨﺘﺸﺮة ﻋﻠﻰ أﺳﻄﺢ ﻗﺮون اﻻﺳﺘﺸﻌﺎر واﻟﺠﺴﻢ، واﻟﺰواﺋﺪ .وﯾﺒﻠﻎ ﻋﺪد ھﺬه اﻟﺸﻌﯿﺮات ﻣﻦ ﺧﻤﺴﯿﻦ أﻟﻒ إﻟﻰ ﻣﺎﺋﺔ أﻟﻒ ﻋﻠﻰ اﻟﻜﻼﺑﺎت وزواﺋﺪ اﻟﻤﺸﻲ ﻓﻘﻂ .وﯾﺸﻐﻞ اﻟﻘﻄﻌﺔ اﻟﻘﺎﻋﺪﯾﺔ ﺑﻜﻞ ﻣﻦ ﻗﺮﻧﻲ اﻻﺳﺘﺸﻌﺎر اﻷوﻟﯿﻦ ﻋﻀﻮ اﺗﺰان ﯾﺤﺲ ﺑﻮاﺳﻄﺘﮫ اﻟﺤﯿﻮان درﺟﺔ ﺗﻮازﻧﮫ ﻓﻲ اﻟﻤﺎء. وﯾﺘﻜﻮن ﺟﮭﺎز اﻟﺘﻨﺎﺳﻞ ﻣﻦ زوج ﻣﻦ اﻟﺨﺼﻲ ﻓﻲ اﻟﺬﻛﺮ أو اﻟﻤﺒﺎﯾﺾ ﻓﻲ اﻷﻧﺜﻰ وﺗﻘﻊ ﻓﻲ اﻟﺠﺰء اﻟﻈﮭﺮي ﻣﻦ اﻟﺠﺴﻢ ،وﯾﻤﺘﺪ ﻣﻨﮭﺎ زوج ﻣﻦ اﻟﻘﻨﻮات ﻛﻞ ﻣﻨﮭﺎ ﺗﻔﺘﺢ ﺑﻔﺘﺤﺔ ﺧﺎرﺟﯿﺔ ﻋﻠﻰ ﻗﺎﻋﺪة زاﺋﺪة اﻟﻤﺸﻲ اﻟﺜﺎﻟﺜﺔ ﻓﻲ اﻷﻧﺜﻰ وزاﺋﺪة اﻟﻤﺸﻲ اﻟﺨﺎﻣﺴﺔ ﻓﻲ اﻟﺬﻛﺮ .وﯾﻤﻜﻦ ﺗﻤﯿﯿﺰ اﻟﺠﻨﺴﯿﻦ ﻣﻦ ﻣﻜﺎن اﻟﻔﺘﺤﺎت اﻟﺘﻨﺎﺳﻠﯿﺔ ،وﻛﺬﻟﻚ ﺑﺘﺮﻛﯿﺐ اﻟﺰاﺋﺪة اﻟﺒﻄﻨﯿﺔ اﻷوﻟﻰ .وﻓﻲ ﻋﻤﻠﯿﺔ اﻟﺴﻔﺎد ﯾﻀﻊ اﻟﺬﻛﺮ 159
اﻟﺤﯿﻮاﻧﺎت اﻟﻤﻨﻮﯾﺔ ﻓﻲ ﺣﻮاﻓﻆ ﻣﻐﺰﻟﯿﺔ اﻟﺸﻜﻞ ﺗﻌﺮف ﺑﺤﺎﻣﻼت اﻟﻤﻨﻰ ﯾﻮﺟﮭﮭﺎ ﻗﺮب ﻓﺘﺤﺎت اﻷﻧﺜﻰ، وﯾﺘﻢ إﺧﺼﺎب اﻟﺒﻮﯾﻀﺎت ﺧﻼل ﻣﺮورھﺎ ﻟﻠﺨﺎرج ،وﺗﻠﺘﺼﻖ اﻟﺒﻮﯾﻀﺎت اﻟﻤﺨﺼﺒﺔ ﺑﺈﻓﺮاز ﻟﺰج ﺑﺰواﺋﺪ اﻟﻌﻮم ﻓﻲ اﻷﻧﺜﻰ ،وﺗﺒﻘﻰ ﻟﺬﻟﻚ ﺟﯿﺪة اﻟﺘﮭﻮﯾﺔ ﻧﺘﯿﺠﺔ ﺣﺮﻛﺔ زواﺋﺪ اﻟﻌﻮم.وﯾﻔﻘﺲ اﻟﺼﻐﺎر ﻣﻦ اﻟﺒﯿﺾ ﻓﻲ ﺷﻜﻞ ﻗﺮﯾﺐ اﻟﺸﺒﮫ ﺑﺎﻟﺤﯿﻮان اﻟﺒﺎﻟﻎ.
اﻟﺘﻜﺎﺛﺮ واﻟﻨﻤﻮ أوﺿﺤﺖ اﻟﺪراﺳﺎت اﻟﺘﻲ ﺗﻤﺖ ﻋﻠﻰ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻓﻲ ﻣﺼﺮ أن ﻟﮫ ﻣﻌﺪل ﻧﻤﻮ ﺳﺮﯾﻊ أﻛﺜﺮ ﻣﻤﺎ ﺗﻢ ﺗﺴﺠﯿﻠﮫ ﻓﻲ ﺑﯿﺌﺘﮫ اﻷﺻﻠﯿﺔ ﺑﺠﻨﻮب أﻣﺮﯾﻜﺎ اﻟﺸﻤﺎﻟﯿﺔ ،وذﻟﻚ ﺑﻌﺪ أن رﺳﻤﺖ ﻣﻨﺤﻨﯿﺎت اﻟﻨﻤﻮ اﻟﻄﺒﯿﻌﻲ ﻟﻠﺤﯿﻮان ﻓﻲ ﻣﺤﺎﻓﻈﺘﯿﻦ ھﻤﺎ اﻟﻘﺎھﺮة واﻟﻘﻠﯿﻮﺑﯿﺔ ،وﻣﻦ ﺧﻼل ﺗﺤﻠﯿﻞ اﻷﻃﻮال ﺷﮭﺮﯾﺎً .ﻛﻤﺎ أﺷﺎرت دراﺳﺔ ﻗﯿﻢ ﻣﻌﺎﻣﻞ اﻟﺤﺎﻟﺔ ) ( Coefficient Conditionﻟﻠﺤﯿﻮان إﻟﻰ ﻣﻼءﻣﺔ ﺑﯿﺌﺘﮫ اﻟﺠﺪﯾﺪة ) ﺷﺒﻜﺔ ﻧﮭﺮ اﻟﻨﯿﻞ ( ﻟﺒﻘﺎﺋﮫ وﻧﻤﻮه وﺗﻜﺎﺛﺮه ﻣﻦ ﺣﯿﺚ ﺗﻮاﻓﺮ اﻟﻐﺬاء اﻟﻤﻨﺎﺳﺐ ﻣﻊ ﺑﺎﻗﻲ اﻟﻈﺮوف اﻟﻤﻌﯿﺸﯿﺔ اﻟﻤﻄﻠﻮﺑﺔ ﻟﮫ ﻣﻊ ﻏﯿﺎب أﻋﺪاﺋﮫ اﻟﻄﺒﯿﻌﯿﺔ. وﯾﺨﺘﻠﻒ ﺣﺠﻢ وﻧﻤﻮ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻣﻦ ﻣﻜﺎن إﻟﻰ آﺧﺮ ،ﻓﻘﺪ وﺟﺪ أﻧﮫ يﺻﻞ إﻟﻰ ﺣﻮاﻟﻲ 105م م ﻓﻲ اﻟﻄﻮل ،وﯾﻌﯿﺶ ﻟﻤﺪة ﺛﻼث ﺳﻨﻮات ﺗﻘﺮﯾﺒﺎ ﻓﻲ ﺑﻌﺾ اﻟﺒﯿﺌﺎت ،وﻟﻤﺪة ﻣﻦ 2– 1ﻋﺎم أو ﻓﻘﻂ ﻓﻲ ﻣﻨﺎﻃﻖ أﺧﺮى .وﺗﻨﻤﻮ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﺑﺼﻮرة ﻣﺘﻘﻄﻌﺔ ﺗﺘﺨﻠﻠﮭﺎ ﻋﻤﻠﯿﺔ ﺧﻠﻊ اﻧﺴﻼخ اﻟﮭﯿﻜﻞ اﻟﺨﺎرﺟﻲ ،وﺗﺒﺪأ ھﺬه اﻟﻌﻤﻠﯿﺔ ﺑﺤﺪوث ﺷﻖ ﻓﻲ اﻟﻨﺎﺣﯿﺔ اﻟﻈﮭﺮﯾﺔ ﻣﻦ اﻟﮭﯿﻜﻞ اﻟﺨﺎرﺟﻲ ﺑﯿﻦ ﻣﻨﻄﻘﺔ اﻟﺒﻄﻦ وﻣﻨﻄﻘﺔ اﻟﺼﺪر وﯾﺴﺤﺐ اﻟﺤﯿﻮان ﻧﻔﺴﮫ ﻣﻦ ﺧﻼل ھﺬا اﻟﺸﻖ ﺗﺎرﻛﺎً اﻟﻘﺸﺮة اﻟﺼﻠﺒﺔ ،وﯾﺒﺪأ اﻟﺤﯿﻮان ﻓﻲ ﺗﻜﻮﯾﻦ ھﯿﻜﻞ ﺧﺎرﺟﻲ ﺟﺪﯾﺪ ﺑﻌﺪ أن ﯾﺄوي إﻟﻰ ﻣﻜﺎن آﻣﻦ ﻧﻈﺮا ﻟﺮﺧﺎوة اﻟﮭﯿﻜﻞ ﻣﻤﺎ ﯾﻌﺮﺿﮫ ﻟﺨﻄﺮ اﻻﻓﺘﺮاس ﺧﻼل ﺗﻠﻚ اﻟﻔﺘﺮة. وﺗﺆﺛﺮ اﻟﻈﺮوف واﻟﻌﻮاﻣﻞ اﻟﺒﯿﺌﯿﺔ ﻓﻲ ﻋﻤﻠﯿﺔ اﻻﻧﺴﻼخ واﻟﻨﻤﻮ وﺗﺘﺎﺑﻊ ﻣﺮاﺣﻞ دورة ﺣﯿﺎة اﻻﺳﺘﺎﻛﻮزا ﺑﻮﺟﮫ ﻋﺎم .وأھﻢ ھﺬه اﻟﻌﻮاﻣﻞ درﺟﺔ اﻟﺤﺮارة اﻟﺘﻲ ﺗﺆﺛﺮ ﺑﺪرﺟﺔ ﻣﺒﺎﺷﺮة ﻋﻠﻰ ﺟﻤﯿﻊ اﻟﻌﻤﻠﯿﺎت اﻟﺤﯿﻮﯾﺔ ﻟﻠﺤﯿﻮان وﺑﺨﺎﺻﺔ ﻧﻤﻮه وﺗﻜﺎﺛﺮه ،وﻣﻦ اﻟﺪراﺳﺎت اﻟﺘﻲ أﺟﺮﯾﺖ ﺗﺒﯿﻦ أﻧﮫ ﻛﻠﻤﺎ ﺗﺰﯾﺪ درﺟﺔ اﻟﺤﺮارة ﯾﺰﯾﺪ اﻟﻨﻤﻮ إﻟﻰ اﻟﺤﺎﻟﺔ اﻟﻤﺜﻠﻰ ﺑﻌﺪھﺎ ﺗﺰﯾﺪ ﻧﺴﺒﺔ اﻟﻤﻮت ،وﯾﺘﻜﻮن ﻣﺎ ﯾﺴﻤﻲ ﺑﻤﻨﺤﻨﻰ اﻟﺠﺮس .ﻛﻤﺎ ﺳﺠﻞ ھﺬا اﻟﻨﻮع ﻣﻦ اﻻﺳﺘﺎﻛﻮزا أﻋﻠﻰ ﻣﻌﺪﻻت ﻧﻤﻮ ﺑﯿﻦ درجﺗﻰ 30 ، 25 ﻣﺌﻮﯾﺔ ﺗﺤﺖ اﻟﻈﺮوف اﻟﻤﻌﻤﻠﯿﺔ . أﻣﺎ ﻋﻦ ﺗﺄﺛﯿﺮ اﻷﻛﺴﺠﯿﻦ اﻟﺬاﺋﺐ ﻓﻘﺪ وﺟﺪ أﻧﮫ ﯾﺠﺐ أن ﯾﻜﻮن ﺗﺮﻛﯿﺰه أﻋﻠﻰ ﻣﻦ 3ﺟﺰء ﻓﻲ اﻟﻤﻠﯿﻮن ﻟﻜﻲ ﯾﻨﻤﻮ اﻟﺤﯿﻮان أﻓﻀﻞ ﻧﻤﻮ ﻛﻤﺎ ﺗﺘﺮاوح درﺟﺔ اﻷس اﻟﮭﯿﺪروﺟﯿﻨﻲ اﻟﻤﺜﻠﻰ ﻟﺒﻘﺎﺋﮫ وﻧﻤﻮه ﺑﯿﻦ . 7.5 – 6.5ﻛﻤﺎ وﺟﺪ أﯾﻀﺎ أن ﻋﻨﺼﺮ اﻟﻜﺎﻟﺴﯿﻮم ﻣﻦ أھﻢ اﻟﻌﻨﺎﺻﺮ اﻟﺘﻲ ﻟﮭﺎ دور اﯾﺠﺎﺑﻲ وھﺎم ﻓﻲ ﻋﻤﻠﯿﺔ إﻋﺎدة ﺑﻨﺎء اﻟﮭﯿﻜﻞ اﻟﺨﺎرﺟﻲ ﻟﻠﺤﯿﻮان اﻟﻤﻨﺴﻠﺦ .ﺣﯿﺚ ﯾﺪﺧﻞ ﻓﻲ ﺑﻨﺎء اﻟﻜﯿﻮﺗﯿﻦ اﻟﻤﺘﺼﻠﺐ اﻟﺬي ﯾﺤﻤﻲ ﺟﺴﻢ اﻟﺤﯿﻮان. 160
ﻛﻤﺎ ﯾﻈﮭﺮ ﺗﺄﺛﯿﺮ اﻟﻜﺜﺎﻓﺔ اﻟﻌﺪدﯾﺔ ﻋﻠﻰ ﻧﻤﻮ وﺑﻘﺎء اﻻﺳﺘﺎﻛﻮزا ﻣﻦ ﺧﻼل ﺑﻌﺾ اﻟﺪراﺳﺎت اﻟﺘﻲ أﺟﺮﯾﺖ ﺗﺤﺖ اﻟﻈﺮوف اﻟﻤﻌﻤﻠﯿﺔ ،وﺗﺒﯿﻦ أن اﻟﻜﺜﺎﻓﺎت اﻟﻌﺪدﯾﺔ اﻟﻌﺎﻟﯿﺔ ﺗﺜﺒﻂ اﻟﻨﻤﻮ وﺗﺰﯾﺪ ﻣﻦ ﻧﺴﺒﺔ اﻟﻤﻮت ﻟﮭﺬا اﻟﺤﯿﻮان . وﺗﺒﯿﻦ ﻛﺬﻟﻚ أن ﻧﻮﻋﯿﺔ اﻟﻄﻌﺎم واﻟﺘﻐﺬﯾﺔ ﻟﮭﻤﺎ ﺗﺄﺛﯿﺮ ﻣﺒﺎﺷﺮ ﻋﻠﻰ ﻋﻤﻠﯿﺔ ﻧﻤﻮ اﻻﺳﺘﺎﻛﻮزا ،وﺗﺘﻤﺜﻞ و اﻟﺪھﻮن اﻟﺘﻐﺬﯾﺔ ﻓﻲ اﺣﺘﯿﺎﺟﺎت اﻻﺳﺘﺎﻛﻮزا ﻣﻦ اﻟﻌﻨﺎﺻﺮ اﻟﻐﺬاﺋﯿﺔ اﻟﻤﺨﺘﻠﻔﺔ ،ﻣﺜﻞ اﻟﺒﺮوﺗﯿﻦ واﻟﻜﺮﺑﻮھﯿﺪرات وﻏﯿﺮھﺎ ﻣﻦ اﻟﻌﻨﺎﺻﺮ اﻟﻐﺬاﺋﯿﺔ اﻷﺧﺮى .ﻓﻔﻲ دراﺳﺔ ﻣﻌﻤﻠﯿﺔ أﻇﮭﺮت اﻟﻨﺘﺎﺋﺞ ان أﻓﻀﻞ ﻧﺴﺐ ﻟﺘﻐﺬﯾﺔ ھﺬا اﻟﺤﯿﻮان ھﻲ ﻣﻦ % 26 -22ﺑﺮوﺗﯿﻦ % 6 ،دھﻮن ،ﻣﻦ % 41 – 36 ﻛﺮﺑﻮھﯿﺪرات وﻣﻦ 2.9 – 2.4ﻛﺎﻟﻮرى ﻟﻜﻞ ﺟﺮام ﻃﺎﻗﺔ .وﻓﻰ دراﺳﺔ ﻣﻌﻤﻠﯿﺔ أﺧﺮى ﺗﺒﯿﻦ أن ﻧﺴﺒﺔ اﻟﺪھﻮن ، % 10 – 2و %30ﺑﺮوﺗﯿﻦ ﻓﻲ اﻟﻌﻠﯿﻘﺔ ،ﺗﺜﺒﻂ ﻧﻤﻮ اﻻﺳﺘﺎﻛﻮزا ﺑﯿﻨﻤﺎ ﻧﻔﺲ اﻟﻨﺴﺒﺔ ﻓﻲ ﻋﻠﯿﻖ ﺑﮭﺎ %40ﺑﺮوﺗﯿﻦ ﺗﺤﺴﻦ ﻣﻦ ﻧﻤﻮ اﻟﺤﯿﻮان .ﻛﻤﺎ أن إﺿﺎﻓﺔ اﻟﻔﯿﺘﺎﻣﯿﻨﺎت ) ( %3 –2.8ﺗﺤﺴﻦ ة ﻣﻦ ﻋﻤﻠﯿﺔ اﻟﻨﻤﻮ .وﻣﻦ ﻧﺎﺣﯿﺔ أﺧﺮى وﺟﺪ أن ﻋﺪم إﺿﺎﻓﺔ أي ﻓﯿﺘﺎﻣﯿﻨﺎت ﯾﺜﺒﻂ ﻧﻤﻮ اﻟﺤﯿﻮان .وﻋﻠﻰ اﻟﻌﻜﺲ ﻋﺪم إﺿﺎﻓﺔ اﻷﻣﻼح اﻟﻤﻌﺪﻧﯿﺔ ﻓﻲ ﻋﻠﯿﻘﮫ اﻻﺳﺘﺎﻛﻮزا ﻟﯿﺲ ﻟﮫ ﺗﺄﺛﯿﺮ اﯾﺠﺎﺑﻲ ﻋﻠﻰ اﻟﻨﻤﻮ. أﻣﺎ م ن ﻧﺎﺣﯿﺔ اﻟﺨﺼﻮﺑﺔ ﻓﻘﺪ وﺟﺪ أن ھﺬا اﻟﺤﯿﻮان ﻓﻲ اﻟﺒﯿﺌﺔ اﻟﻤﺼﺮﯾﺔ ﻟﮫ ﻣﻮﺳﻤﺎن ﻣﻨﻔﺼﻼن ﻟﻠﺘﻜﺎﺛﺮ ﺣﯿﺚ ﺗﻀﻊ اﻷﻧﺜﻰ اﻟﺒﯿﺾ ﻓﻲ ﻣﻨﺘﺼﻒ اﻟﺮﺑﯿﻊ ) اﺑﺮﯾﻞ ( وﻓﻰ ﻧﮭﺎﯾﺔ اﻟﺨﺮﯾﻒ )ﻧﻮﻓﻤﺒﺮ( ، وﯾﺘﺮاوح ﻋﺪد اﻟﺒﯿﺾ ﺑﯿﻦ 700 -100ﺑﯿﻀﺔ ،ﺛﻢ ﺗﺪﺧﻞ اﻷﻧﺜﻰ ﻓﻲ ﻗﻨﻮات ﺗﺤﻔﺮھﺎ ﻓﻲ ﺑﺪاﯾﺔ 1ﻣﺘﺮ إﻟﻰ 2.5ﻣﺘﺮ وﯾﻔﻘﺲ ﻓﺼﻞ اﻟﺸﺘﺎء ﻋﻠﻰ ﺣﻮاف اﻟﻤﺠﺮى اﻟﻤﺎﺋﻲ ﻗﺪ ﯾﺼﻞ ﻃﻮﻟﮭﺎ ﻣﻦ اﻟﺒﯿﺾ إﻟﻰ اﻟﺼﻐﺎر ﺑﻌﺪ ﺣﻮاﻟﻲ أﺳﺒﻮﻋﯿﻦ إﻟﻲ ﺛﻼﺛﺔ ،وﯾﻌﺘﻤﺪ اﻟﻔﻘﺲ أﯾﻀﺎ ﻋﻠﻰ اﻟﻈﺮوف اﻟﺒﯿﺌﯿﺔ اﻟﻤﺤﯿﻄﺔ . وﻗﺪ ﺻﻤﻤﺖ ﻋﺪة دراﺳﺎت ﻣﻌﻤﻠﯿﺔ ﺗﻮﺿﺢ ﺗﺄﺛﯿﺮ اﻟﻈﺮوف اﻟﺒﯿﺌﯿﺔ اﻟﻤﺤﯿﻄﺔ ﺑﺎﻟﺤﯿﻮان ﻋﻠﻰ ﻋﻤﻠﯿﺔ اﻟﺘﻜﺎﺛﺮ واﻟﺘﺰاوج ﺛﻢ وﺿﻊ اﻟﺒﯿﺾ .وأوﺿﺤﺖ أن اﻟﺘﺰاوج اﻻﺧﺘﯿﺎري ﯾﻨﺠﺢ ﺑﻨﺴﺒﺔ %100وﻻ ﯾﺘﺠﺎوز % 10وﻓﯿﺎت وﯾﻨﺘﺞ ﺣﻮاﻟﻲ 600ﺑﯿﻀﺔ أﻣﺎ اﻟﺘﺰاوج اﻻﺟﺒﺎرى ﻓﻼ ﺗﺰﯾﺪ ﻧﺴﺒﺔ ﻧﺠﺎﺣﮫ ﻋﻦ ، % 50وﺳﺠﻞ أﻛﺜﺮ ﻣﻦ %50وﻓﯿﺎت وﻧﺎﺗﺞ ﺣﻮاﻟﻲ 250ﺑﯿﻀﺔ ) %80ﻓﺎﻗﺪ ﻓﻲ اﻟﺒﯿﺾ( . ﻛﻤﺎ ﺗﺒﯿﻦ أﯾﻀﺎ أن ﻋﺪد اﻟﺒﯿﺾ ﯾﺘﻨﺎﺳﺐ ﺗﻨﺎﺳﺒﺎً ﻃﺮدﯾﺎ ﻣﻊ ﺣﺠﻢ اﻷﻧﺜﻰ ،ﺣﯿﺚ أن اﻷﻧﺜﻰ اﻟﺘﻲ ﻣﺘﻮﺳﻂ ﺣﺠﻤﮭﺎ ) اﻟﻄﻮل اﻟﻜﻠﻰ ( 60ﻣﻢ ﺗﻀﻊ 250ﺑﯿﻀﺔ ،أﻣﺎ اﻟﺘﻲ ﻃﻮﻟﮭﺎ 90ﻣﻢ ﻓﺘﻀﻊ ﺣﻮاﻟﻲ 300ﺑﯿﻀﺔ وﯾﺼﻞ ﻋﺪد اﻟﺒﯿﺾ إﻟﻰ 600ﺑﯿﻀﺔ ﻟﻸﻧﺜﻰ اﻟﺘﻲ ﻣﺘﻮﺳﻂ ﻃﻮﻟﮭﺎ اﻟﻜﻠﻰ 120ﻣﻢ . وﯾﺘﺮاوح ﻗﻄﺮ اﻟﺒﯿﻀﺔ ﻣﻦ 3 – 1ﻣﻢ . وﺗﺘﺤﺪد ﻋﻤﻠﯿﺔ اﻟﻨﻀﺞ اﻟﺠﻨﺴﻲ ﻟﻸﻧﺜﻰ ﺑﺎﻟﺘﻐﯿﺮات اﻟﺘﻲ ﺗﺤﺪث ﻓﻲ اﻟﻤﻨﺎﺳﻞ ﻣﻦ ﺣﯿﺚ ﺣﺠﻢ وﺗﻐﯿﺮ ﻓﻲ ﻟﻮن الم ﺑﯿﺾ ،ﻓﻔﻲ اﻟﺒﺪاﯾﺔ ﯾﻜﻮن ﻟﻮن اﻟﻤﺒﯿﺾ ﻓﺎﺗﺤﺎ ﺛﻢ ﯾﺼﺒﺢ داﻛﻨﺎً ﺗﺪرﯾﺠﯿﺎً و ﯾﻜﺒﺮ ﻓﻲ اﻟﺤﺠﻢ ﻗﺒﻞ ﻋﻤﻠﯿﺔ اﻟﺘﻜﺎﺛﺮ . وﺗﺤﺘﺎج اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ إﻟﻰ 11اﻧﺴﻼخ ﻋﻠﻰ اﻷﻗﻞ ﻟﺘﺼﻞ إﻟﻰ اﻟﻨﻀﺞ اﻟﺠﻨﺴﻲ وﯾﻌﺘﻤﺪ ھﺬا أﯾﻀﺎ ﻋﻠﻰ اﻟﻈﺮوف اﻟﺒﯿﺌﯿﺔ اﻟﻤﺤﯿﻄﺔ اﻟﺘﻲ ﺳﺒﻖ ذﻛﺮھﺎ .
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ﻛﻤﺎ ﺗﻌﺘﻤﺪ ﻋﻤﻠﯿﺔ ﻧﻀﻮج اﻟﻤﻨﺎﺳﻞ ﻋﻠﻰ اﻟﮭﺮﻣﻮﻧﺎت اﻟﺠﻨﺴﯿﺔ اﻟﺘﻲ ﯾﻔﺮزھﺎ ﻛﻞ ﻣﻦ اﻟﺬﻛﺮ واﻷﻧﺜﻰ ، وﻓﻲ اﻟﺬﻛﺮ ﯾﻜﻮن ﻣﺴﺘﻮى ھﺮﻣﻮن اﻟﺘﯿﺴﺘﻮﺳﺘﯿﺮون أﻋﻠﻰ ﻣﻦ ھﺮﻣﻮن اﻻﺳﺘﺮادﯾﻮل .وﯾﻜﻮن ﻣﻌﻈﻢ ﺗﺮﻛﯿﺰ ھﺮﻣﻮن اﻻﺳﺘﺮادﯾﻮل ﻓﻲ ﺳﺎق اﻟﻌﯿﻦ وﻛﻤﯿﺔ ﻗﻠﯿﻠﺔ ﻣﻨﮫ ﺗﻔﺮزھﺎ اﻟﻤﻨﺎﺳﻞ .وأﺛﻨﺎء ﻋﻤﻠﯿﺔ اﻻﻧﺴﻼخ ﺗﺘﺄرﺟﺢ ﻧﺴﺐ اﻟﮭﺮﻣﻮﻧﺎت اﻟﺠﻨﺴﯿﺔ .ﻓﻔﻲ ﺑﺪاﯾﺔ اﻻﻧﺴﻼخ ﯾﺰﯾﺪ ھﺮﻣﻮن اﻻﺳﺘﺮادﯾﻮل اﻟﻰ % 50ﻓﻲ اﻟﻤﻨﺎﺳﻞ واﻟﻐﺪة اﻟﮭﺎﺿﻤﺔ واﻟﺤﺒﻞ اﻟﻌﺼﺒﻲ واﻟﻌﻀﻼت ،ﺑﯿﻨﻤﺎ ﯾﺰﯾﺪ اﻟﺘﯿﺴﺘﻮﺳﺘﯿﺮون ﺑﻨﺴﺒﺔ % 79 -11ﻓﻲ ھﺬه اﻷﻋﻀﺎء ،وﯾﻘﻞ ﻟﻠﺜﻠﺚ ﻓﻲ ﺳﺎق اﻟﻌﯿﻦ واﻟﻐﺪد اﻟﺨﻀﺮاء .وﺑﻌﺪ ﻋﻤﻠﯿﺔ اﻻﻧﺴﻼخ ﯾﺰﯾﺪ اﻻﺳﺘﺮادﯾﻮل إﻟﻰ %60ﻓﻲ اﻟﻘﻠﺐ ،واﻟﻐﺪة اﻟﮭﺎﺿﻤﺔ وﺳﺎق اﻟﻌﯿﻦ واﻟﮭﯿﻜﻞ اﻟﺨﺎرﺟﻲ ،ﺑﯿﻨﻤﺎ ﯾﻘﻞ اﻟﺘﯿﺴﺘﻮﺳﺘﯿﺮون إﻟﻰ % 66ﻓﻲ اﻟﻤﻨﺎﺳﻞ واﻟﻰ %42ﻓﻰ اﻟﻌﻀﻼت . وﯾﺘﻀﺢ ﺟﻠﯿﺎً ﻣﻤﺎ ﺳﺒﻖ أن ﻋﻤﻠﯿﺔ ﻧﻤﻮ وﺗﻜﺎﺛﺮ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﯾﺘﺤﻜﻢ ﻓﯿﮭﺎ اﻟﻈﺮوف اﻟﺒﯿﺌﯿﺔ اﻟﻤﺤﯿﻄﺔ إﻟﻰ ﺟﺎﻧﺐ ﻋﻮاﻣﻞ ﻓﺴﯿﻮﻟﻮﺟﯿﺔ وﺣﯿﻮﯾﺔ داﺧﻞ اﻟﺤﯿﻮان ﻧﻔﺴﮫ .وﻟﺬﻟﻚ ﯾﺠﺐ إﺟﺮاء اﻟﻤﺰﯾﺪ ﻣﻦ اﻟﺪراﺳﺎت ﻟﺠﻤﻊ ﻣﻌﻠﻮﻣﺎت ﻛﺎﻓﯿﺔ ﺣﻮل ھﺬا اﻟﺤﯿﻮان اﻟﺬي اﺳﺘﻮﻃﻦ ﻣﯿﺎھﻨﺎ اﻟﻤﺼﺮﯾﺔ. اﻟﺘﻜﯿﻒ اﻟﻔﺴﯿﻮﻟﻮﺟﻲ ﻣﻊ اﻟﺒﯿﺌﺔ واﻟﻤﻨﺎﻋﺔ ) (١اﺳﺘﻘﺒﺎل وﻧﻘﻞ اﻟﻤﺆﺛﺮات اﻟﺨﺎرﺟﯿﺔ : ﯾﻮﺟﺪ ﻋﻠﻰ ﺟﺴﻢ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻣﺠﺴﺎت ﺧﺎرﺟﯿﺔ ﺗﺴﺘﻄﯿﻊ ﻣﻦ ﺧﻼﻟﮭﺎ رﺻﺪ اﻟﺘﻐﯿﺮات اﻟﺒﯿﺌﯿﺔ ،وﻛﻞ ﻣﻨﮭﺎ ﻋﺒﺎرة ﻋﻦ ﻣﺴﺘﻘﺒﻞ ﺣﺴﻲ أو ﻣﺠﻤﻮﻋﺔ ﻣﻦ اﻟﺨﻼﯾﺎ اﻟﻤﺘﺨﺼﺼﺔ اﻟﺘﻲ ﺗﺴﺘﺠﯿﺐ ﻟﻠﺘﻐﯿﺮات اﻟﺒﯿﺌﯿﺔ اﻟﻜﯿﻤﯿﺎﺋﯿﺔ واﻟﺤﺮارﯾﺔ. وﯾﺘﻢ اﺳﺘﻘﺒﺎل اﻹﺷﺎرات اﻟﺨﺎرﺟﯿﺔ ﻣﻦ ﺧﻼل اﻟﻤﺴﺘﻘﺒﻼت اﻟﻤﻮﺟﻮدة ﻋﻠﻰ اﻟﺴﻄﺢ اﻟﺨﺎرﺟﻲ ﻟﻠﺨﻼﯾﺎ ..ﻓﮭﻨﺎك ﺑﻌﺾ اﻟﻤﺴﺘﻘﺒﻼت اﻟﺘﻲ ﺗﺘﺄﺛﺮ ﺑﺄي ﺗﻐﯿﺮ ﺑﺴﯿﻂ ﻓﻲ اﻟﺒﯿﺌﺔ اﻟﻤﺤﯿﻄﺔ وھﻨﺎك ﻧﻮع آﺧﺮ ﯾﺤﺘﻮى ﻋﻠﻰ ﺑﻌﺾ اﻟﺠﺰﯾﺌﺎت اﻟﺘﻲ يﺗﻐﯿﺮ ﺷﻜﻠﮭﺎ ﻧﺘﯿﺠﺔ ﻟﻠﻤﺆﺛﺮ اﻟﺨﺎرﺟﻲ ..ﻋﻠﻰ ﺳﺒﯿﻞ اﻟﻤﺜﺎل اﻟﻤﺴﺘﻘﺒﻼت اﻟﺒﺼﺮﯾﺔ اﻟﻤﻮﺟﻮدة ﻓﻲ اﻟﻌﯿﻦ اﻟﻤﺮﻛﺒﺔ ﻻﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﺣﯿﺚ ﺗﻮﺟﺪ ﺟﺰﯾﺌﺎت اﻟﺮودوﺑﺴﯿﻦ ) (Rhodopsinاﻟﺘﻲ ﺗﺘﻔﺎﻋﻞ ﻣﻊ ﻓﻮﺗﻮﻧﺎت اﻟﻀﻮء ﻣﺤﺪﺛﺔ ﺗﻐﯿﺮ ﻓﻲ ﺷﻜﻞ اﻟﺠﺰء اﻟﺬي ﯾﻨﺘﺞ ﻋﻨﮫ ﺗﻐﯿﺮ ﻓﻲ ﻧﺸﺎط اﻟﺨﻠﯿﺔ وﺑﺪء ﺳﻠﺴﻠﺔ ﻣﻦ اﻟﺘﻔﺎﻋﻼت اﻟﻜﯿﻤﯿﺎﺋﯿﺔ ﻋﻠﻰ ﻏﺸﺎء اﻟﺨﻠﯿﺔ ،ﺣﯿﺚ ﯾﺘﺒﻊ ذﻟﻚ ﺗﻐﯿﺮ ﻓﻲ ﺗﻮزﯾﻊ اﻻﯾﻮﻧﺎت ﻣﻦ ﺧﻼل ﻏﻠﻖ وﻓﺘﺢ ﻗﻨﻮات ﻣﻌﯿﻨﺔ وھﺬه اﻟﺘﻐﯿﺮات ھﻲ اﻟﻨﺘﯿﺠﺔ اﻟﻨﮭﺎﺋﯿﺔ ﻟﻠﻤﺆﺛﺮ اﻟﺨﺎرﺟﻲ اﻟﺬي ﯾﻤﺜﻞ اﻟﻄﺮﯾﻘﺔ اﻟﺘﻲ ﺗﻨﺘﻘﻞ ﺑﮭﺎ ھﺬه اﻟﻤﺆﺛﺮات ﻣﻦ اﻟﺨﺎرج إﻟﻰ ﺧﻼﯾﺎ اﻟﺠﺴﻢ . وﯾﺘﻢ ﺗﺮﺟﻤﺔ اﻹﺷﺎرات اﻟﺨﺎرﺟﯿﺔ ﻷوﺿﺢ ﺻﻮرة ﺗﻌﺒﺮ ﻋﻦ ﺷﻜﻞ وﺷﺪة ھﺬا اﻟﻤﺆﺛﺮ ﺣﺘﻰ ﯾﺴﺘﻄﯿﻊ اﻟﺠﮭﺎز اﻟﻌﺼﺒﻲ اﻟﺘﻌﺎﻣﻞ ﻣﻌﮫ . ) (2اﻟﺘﺄﻗﻠﻢ اﻟﻔﺴﯿﻮﻟﻮﺟﻲ : ﺗﺘﻢ اﻟﺘﮭﻮﯾﺔ ﻓﻲ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻋﻦ ﻃﺮﯾﻖ ﺣﺪوث ذﺑﺬﺑﺎت واﻧﺤﺮاف اﻟﻐﻄﺎء اﻟﺨﯿﺸﻮﻣﻲ اﻟﻤﺘﺼﻞ ﺑﺎﻟﻐﺮﻓﺔ الﺧﯿﺸﻮﻣﻲة ﻣﻦ ﺧﻼل ﻓﺘﺤﺘﯿﻦ ﻋﻠﻰ ﺟﺎﻧﺒﻲ ا ﻟﺮأس .وﯾﺘﻢ اﺧﺬ اﻷﻛﺴﺠﯿﻦ ﻣﻦ اﻟﻮﺳﻂ اﻟﺨﺎرﺟﻲ ﻋﻦ ﻃﺮﯾﻖ اﻟﺘﺪرج ﻓﻲ ﻧﺴﺒﺔ اﻷﻛﺴﺠﯿﻦ اﻟﻤﻮﺟﻮد ﻓﻰ اﻟﮭﯿﻤﻮﻟﯿﻒ ) (haemolymphواﻟﻤﯿﺎه اﻟﻤﺴﺘﻘﺒﻠﺔ ﺑﻮاﺳﻄﺔ ﻧﻈﺎم اﻟﺘﺒﺎدل ﻣﺘﻌﺪد اﻟﺸﺮاﯾﯿﻦ ..ﯾﺘﻢ ﻧﻘﻞ اﻷﻛﺴﺠﯿﻦ ﻋﻦ ﻃﺮﯾﻖ اﻟﮭﯿﻤﻮﺳﯿﺎﻧﯿﻦ) (haemocyaninوﻓﯿﮫ ﯾﺘﻢ اﺗﺤﺎد ﺟﺰئ ﻣﻦ اﻟﻨﺤﺎس ﻣﻊ ﻋﺪﯾﺪ
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اﻟﮭﺴﺘﺎدﯾﻦ ﻟﺘﻜﻮﯾﻦ ﺟﺮاب ﯾﺘﺤﺪ ﺑﮫ اﻷﻛﺴﺠﯿﻦ .و ﯾﺘﻢ اﻣﺘﺼﺎص اﻷﻛﺴﺠﯿﻦ ﺑﻮاﺳﻄﺔ اﻟﺨﯿﺎﺷﯿﻢ وإﻃﻼﻗﮫ ﻟﻸﻧﺴﺠﺔ ﺑﺼﻮرة ﺳﺮﯾﻌﺔ وﻓﻌﺎﻟﺔ ﻧﺘﯿﺠﺔ ﻟﻠﺘﻐﯿﺮات اﻟﺪﻗﯿﻘﺔ ﻓﻲ ﺟﺰﯾﺌﺎت اﻟﺒﯿﺌﺔ . ﻛﻤﺎ ﯾﺘﻢ إﺧﺮاج ﺛﺎﻧﻲ أﻛﺴﯿﺪ اﻟﻜﺮﺑﻮن اﻟﻨﺎﺗﺞ ﻋﻦ ﻋﻤﻠﯿﺔ ﺗﻨﻔﺲ اﻟﺨﻼﯾﺎ ﻣﻦ ﺧﻼل اﻟﮭﯿﻤﻮﻟﯿﻤﻒ ﺑﻮاﺳﻄﺔ اﻟﺨﯿﺎﺷﯿﻢ ﻣﺮة أﺧﺮى وﯾﺘﻢ ﺿﺦ اﻟﮭﯿﻤﻮﻟﯿﻤﻒ ﻓﻲ ﺟﺴﻢ اﻟﺤﯿﻮان ﺑﻮاﺳﻄﺔ أذﯾﻦ ﻋﻀﻠﻲ واﺣﺪ ﻣﺘﻌﻠﻖ ﻓﻲ ﻏﺮﻓﺔ ﺟﺎﻣﻌﺔ داﺧﻞ ﺗﺠﻮﯾﻒ اﻟﺘﺎﻣﻮر .وأﺛﻨﺎء ﻋﻤﻠﯿﺔ اﻻﻧﻘﺒﺎض ﯾﺘﻢ ﺿﺦ اﻟﺪم إﻟﻰ أﺟﺰاء اﻟﺠﺴﻢ اﻟﻤﺨﺘﻠﻔﺔ ﻋﻦ ﻃﺮﯾﻖ ﻗﻨﻮات ﺷﺮﯾﺎﻧﯿﺔ ﻣﺘﻔﺮﻋﺔ إﻟﻰ ﻗﻨﻮات اﺻﻐﺮ داﺧﻞ اﻷﻧﺴﺠﺔ .وﯾﺘﻢ ﺟﻤﻊ اﻟﮭﯿﻤﻮﻟﯿﻤﻒ ﺑﻮاﺳﻄﺔ ﺟﯿﻮب ﺻﻐﯿﺮة ﺗﺘﺠﻤﻊ ﻟﺘﻜﻮﯾﻦ ﺟﯿﺐ ﻛﺒﯿﺮ ﺟﺎﻣﻊ وﻣﻨﮫ إﻟﻰ اﻟﺨﯿﺎﺷﯿﻢ ﺣﯿﺚ ﯾﺘﻢ ﺗﻨﻘﯿﺘﮫ ﻣﻦ ﺧﻼل اﻷوردة اﻟﺮﺋﻮﯾﺔ اﻟﻘﻠﺒﯿﺔ وﺗﺼﻞ ﻓﻲ اﻟﻨﮭﺎﯾﺔ إﻟﻰ ﺗﺠﻮﯾﻒ اﻟﻘﻠﺐ وﯾﺪﺧﻞ اﻟﮭﯿﻤﻮﻟﯿﻤﻒ إﻟﻰ اﻷذﯾﻦ ﺧﻼل اﻻﻧﺒﺴﺎط . وﯾﺘﻢ اﻟﺘﺤﻜﻢ ﻓﻲ ﺗﻨﻈﯿﻢ اﻟﻀﻐﻂ اﻷﯾﻮﻧﻲ واﻻﺳﻤﻮ زى ﻓﻲ اﻻﺳﺘﺎﻛﻮزا ﻣﻦ ﺧﻼل اﻟﻐﺸﺎء اﻟﻜﯿﺘﯿﻨﻰ اﻟﺬي ﯾﺤﯿﻂ ﺑﺎﻟﺠﺴﻢ ﺣﯿﺚ اﻧﮫ ﯾﺤﺪد اﻣﺘﺼﺎص اﻟﻤﺎ ء وﻓﻘﺪ اﻷﻣﻼح .وﻓﻲ اﻷﻣﺎﻛﻦ اﻟﺘﻲ ﯾﻜﻮن ﻓﯿﮭﺎ ﻏﺸﺎء اﻟﻜﯿﺘﯿﻦ رﻗﯿﻘﺎ ﻣﺜﻞ اﻟﺨﯿﺎﺷﯿﻢ ﺗﻜﻮن اﻟﻨﻔﺎذﯾﺔ ﻗﻠﯿﻠﺔ ﻧﺴﺒﯿﺎً وﻗﺪ ﯾﻌﻮض ھﺬه اﻟﻨﺴﺒﺔ اﻟﻘﻠﯿﻠﺔ ﻣﻦ ذة. ﺧﻼل ﻋﻤﻠﯿﺔ اﻣﺘﺼﺎص ﻧﺸﻄﺔ ﻓﻲ اﻷﻏﺸﯿﺔ اﻟﻤﻦف وﯾﺘﻢ اﻟﺘﺨﻠﺺ ﻣﻦ اﻟﻤﯿﺎه اﻟﺰاﺋﺪة ﻋﻦ ﻃﺮﯾﻖ ﺟﮭﺎز اﻹﺧﺮاج وھﻮ ﻋﺒﺎرة ﻋﻦ اﻟﻐﺪة اﻟﺨﻀﺮاء أو اﻟﺰﺑﺎﻧﯿﺔ ﻓﻲ ﻗﺎﻋﺪة ﻗﺮن اﻻﺳﺘﺸﻌﺎر اﻟﺜﺎﻧﻲ ،ﻛﻤﺎ ﯾﺘﻢ إﻋﺎدة اﻣﺘﺼﺎص اﻷﻣﻼح ﻣﺮة أﺧﺮى ﻣﻦ ﺧﻼﻟﮭﺎ ،ﺣﯿﺚ ﯾﻮﺟﺪ ﺑﮭﺎ ﻣﺎدة ﻛﯿﺘﯿﻨﯿﺔ وﺑﻌﺾ اﻷﻟﯿﺎف اﻟﺘﻲ ﺗﻌﻤﻞ ﻛﻤﺮﺷﺢ ﯾﺘﻢ ﻣﻦ ﺧﻼﻟﮭﺎ ﻣﺮور اﻟﺠﺰﯾﺌﺎت ذات اﻟﻮزن اﻟﺠﺰﺋﻲ اﻟﺼﻐﯿﺮ ﻛﺎﻟﻤﺎء واﻷﯾﻮﻧﺎت واﻟﻔﻀﻼت اﻟﻨﯿﺘﺮوﺟﯿﻨﯿﺔ وﺑﻌﺾ اﻟﻤﺨﻠﻔﺎت اﻷﺧﺮى وﻻ ﺗﺴﻤﺢ ﺑﻤﺮور اﻟﺨﻼﯾﺎ واﻟﺠﺰﯾﺌﺎت ذات اﻟﺤﺠﻢ اﻟﻜﺒﯿﺮ ﻣﺜﻞ اﻟﺒﺮوﺗﯿﻨﺎت . اﻟﻤﻨﺎﻋﺔ : ﯾﺨﺘﻠﻒ ﺟﮭﺎز اﻟﻤﻨﺎﻋﺔ ﻓﻲ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻋﻦ ﻧﻈﯿﺮه ﻓﻲ اﻟﻔﻘﺎرﯾﺎت ﻓﻲ اﻧﮫ ﯾﻌﺘﻤﺪ ﻋﻠﻰ اﻟﻤﻨﺎﻋﺔ اﻟﺬاﺗﯿﺔ ﻟﺼﺪ ھﺠﻮم اﻟﻜﺎﺋﻨﺎت اﻟﺪﻗﯿﻘﺔ اﻟﻐﺎزﯾﺔ ﻛﻤﺎ ﻻ ﯾﻮﺟﺪ ﻓﻲ ﺟﮭﺎز اﻟﻤﻨﺎﻋﺔ أﺟﺴﺎم ﻣﻀﺎدة وﻻ ﻛﺮات دم ﺑﯿﻀﺎء ،ﻟﺬﻟﻚ ﯾﻘﻮم اﻟﮭﯿﻤﻮﺳﯿﺎﻧﯿﻦ ﺑﺎﻟﺪور اﻟﺘﻌﻮﯾﻀﻲ ﻓﻲ ﻧﻘﻞ اﻷﻛﺴﺠﯿﻦ ﻣﻦ اﻟﺠﮭﺎز اﻟﺪوري إﻟﻰ اﻷﻧﺴﺠﺔ .وﻋﻠﻰ اﻟﺮﻏﻢ ﻣﻦ ﻋﺪم وﺟﻮد ﺟﻠﻮﺑﯿﻮﻟﯿﻦ ﻣﻨﺎﻋﻲ ) (Immunoglobulin ﺗﺴﺘﻄﯿﻊ اﻻﺳﺘﺎﻛﻮزا اﻟﺘﻌﺮف ﻋﻠﻰ ﻣﻜﻮﻧﺎت أﻏﺸﯿﺔ اﻟﺨﻼﯾﺎ اﻟﻐﺮﯾﺒﺔ ﻓﻲ اﻟﺒﻜﺘﺮﯾﺎ أو اﻟﻔﻄﺮﯾﺎت ،وﯾﺘﻢ اﻟﺘﻔﺎﻋﻞ اﻟﻤﻨﺎﻋﻲ ﻋﻦ ﻃﺮﯾﻖ ﻣﺎ ﯾﺄﺗﻰ: ) (1ﺗﻜﻮﯾﻦ ﺑﺮوﺗﯿﻦ اﻟﺘﻌﺎرف Pattern recognition proteins ﻋﻨﺪ دﺧﻮل ﺟﺴﻢ ﻏﺮﯾﺐ ﻛﺎﻟﺒﻜﺘﺮﯾﺎ أو اﻟﻔﻄﺮﯾﺎت ﻓﻲ ﺟﺴﻢ اﻻﺳﺘﺎﻛﻮزا ﺗﺴﺘﻄﯿﻊ أن ﺗﺘﻌﺮف ھﺬا اﻟﺒﺮوﺗﯿﻦ اﻟﻐﺮﯾﺐ ﺣﯿﺚ ﺗﺨﺮج ﻧﻮﻋﺎ ﻣﻦ اﻟﺒﻼزﻣﺎ ﺑﺮوﺗﯿﻦ ﻣﻦ اﻟﮭﯿﻤﻮﻟﯿﻤﻒ ﯾﻄﻠﻖ ﻋﻠﯿﮫ BGBP اﻟﺬي ﯾﺘﻌﺮف ﻋﻠﻰ اﻟﺒﺮوﺗﯿﻦ وﯾﺘﺤﺪ ﻣﻌﮫ وﯾﻜﻮن ﻣﺮﻛﺒﺎ ﯾﺘﺤﺪ ﻣﻊ ﻣﺴﺘﻘﺒﻞ ﻣﻌﯿﻦ ﻋﻠﻰ ﺟﺪار اﻟﺠﯿﻮب اﻟﺪﻣﻮﯾﺔ اﻟﺬي ﯾﻨﺸﻂ ﺟﮭﺎز اﻟﻤﻨﺎﻋﺔ .وﯾﺴﺘﻄﯿﻊ ﺑﺮوﺗﯿﻦ اﻟﺘﻌﺎرف ﺗﻤﯿﯿﺰ اﻟﻨﻤﺎذج اﻟﻤﺨﺘﻠﻔﺔ ﻣﻦ ﺑﺮوﺗﯿﻨﺎت اﻟﻤﯿﻜﺮوﺑﺎت . ) (2ﺗﻜﻮﯾﻦ اﻟﺠﻠﻄﺔ Clotting reaction
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ﻧﺘﯿﺠﺔ ﻟﻮﺟﻮد ﺟﮭﺎز دوري ﻣﻔﺘﻮح ﻓﻲ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻓﮭﻲ ﺗﺤﺘﺎج إﻟﻰ أﻧﻈﻤﺔ ﻣﺨﺘﻠﻔﺔ ﻟﺤﺪوث اﻟﺘﺠﻠﻂ ﻟﺤﻤﺎﯾﺘﮭﺎ ﻣﻦ ﻓﻘﺪ اﻟﺪم .وﯾﺘﻜﻮن ﺟﮭﺎز اﻟﺘﺠﻠﻂ ﻓﻲ اﻻﺳﺘﺎﻛﻮزا ﻣﻦ ﻣﺠﻤﻮﻋﺔ ﻣﻦ اﻟﻌﻨﺎﺻﺮ اﻟﻤﻮﺟﻮدة ﻓﻲ اﻟﺒﻼزﻣﺎ واﻟﺨﻼﯾﺎ ،ﺣﯿﺚ ﺗﺤﺘﻮى اﻟﺒﻼزﻣﺎ ﻋﻠﻰ ﻧﻮع ﻣﻦ اﻟﺪھﻮن اﻟﺒﺮوﺗﯿﻨﯿﺔ ﻋﺎﻟﯿﺔ اﻟﻜﺜﺎﻓﺔ ﯾﺴﻤﻰ ﺑﺮوﺗﯿﻦ اﻟﺘﺠﻠﻂ .وﻟﺘﻜﻮﯾﻦ اﻟﺠﻠﻄﺔ ﯾﺘﻢ إﻃﻼق إﻧﺰﯾﻢ ﻣﻌﯿﻦ داﺧﻞ ﺧﻼﯾﺎ اﻟﺪم اﻟﺬي ﯾﻌﺘﻤﺪ ﻧﺸﺎﻃﮫ ﻋﻠﻰ وﺟﻮد اﻟﻜﺎﻟﺴﯿﻮم وﯾﺘﻢ إﻃﻼق ھﺬا اﻹﻧﺰﯾﻢ ﻧﺘﯿﺠﺔ ﻟﺤﺪوث اﻟﺠﺮوح أو اﻟﻌﺪوى اﻟﻤﯿﻜﺮوﺑﯿﺔ .ﺣﯿﺚ ﺗﺘﺤﺪ ﺟﺰﯾﺌﺎت ﺑﺮوﺗﯿﻦ اﻟﺘﺠﻠﻂ ﻣﻊ ﺑﻌﻀﮭﺎ ﻓﻲ وﺟﻮد اﻟﻜﺎﻟﺴﯿﻮم واﻷﻧﺰﯾﻢ ﻟﺘﻜﻮﯾﻦ ﺳﻠﺴﻠﺔ ﻛﺒﯿﺮة ﻣﻦ اﻟﺨﯿﻮط اﻟﻤﺘﺸﺎﺑﻜﺔ ﺗﻮﻗﻒ اﻟﻨﺰﯾﻒ . ) (3اﻟﻤﻨﺎﻋﺔ اﻟﺨﻠﻮﯾﺔ Cellular immunity ﯾﺘﻢ اﻟﺪﻓﺎع اﻟﺨﻠﻮي ﻓﻲ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻋﻦ ﻃﺮﯾﻖ اﻟﺘﮭﺎم أو اﺑﺘﻼع اﻷﺟﺴﺎم اﻟﺪﻗﯿﻘﺔ اﻟﺪﺧﯿﻠﺔ واﻟﻤﯿﻜﺮوﺑﺎت وﺗﻜﻮﯾﻦ ﺣﻮﺻﻠﺔ ﻣﻦ اﻟﺨﻼﯾﺎ ﺣﻮﻟﮭﺎ .وھﺬه اﻟﻌﻤﻠﯿﺔ ھﻲ اﻟﺸﺎﺋﻌﺔ ﻓﻲ ﻣﻌﻈﻢ اﻟﻼﻓﻘﺎرﯾﺎت .وﯾﻮﺟﺪ ﻓﻲ اﻟﮭﯿﻤﻮﻟﻤﻒ ﺛﻼﺛﺔ أﻧﻮاع ﻣﻦ اﻟﺨﻼﯾﺎ ھﻲ اﻟﻤﺤﺒﺒﺔ ) (granularواﻟﺸﻔﺎﻓﺔ ) (hyalineوﻧﺼﻒ اﻟﻤﺤﺒﺒﺔ ) .(semigranularوھﺬه اﻟﺨﻼﯾﺎ ﻗﺎدرة ﻋﻠﻰ اﻟﺘﮭﺎم اﻷﺟﺴﺎم ، opsoninوھﻰ ﻣﻦ أﻧﻮاع ﺑﺮوﺗﯿﻦ اﻟﻐﺮﯾﺒﺔ دﻗﯿﻘﺔ اﻟﺤﺠﻢ وﻛﺬﻟﻚ ﯾﻮﺟﺪ ﻓﻲ اﻟﺒﻼزﻣﺎ ﻣﺎدة اﻟﺘﻌﺎرف ﯾﺴﺎﻋﺪ ﻓﻲ ﻋﻤﻠﯿﺔ اﻻﺑﺘﻼع .وﻋﻨﺪﻣﺎ ﯾﻜﻮن اﻟﻄﻔﯿﻠﻲ ﻛﺒﯿﺮ اﻟﺤﺠﻢ وﻻ ﯾﻤﻜﻦ اﺑﺘﻼﻋﮫ ﺗﺘﻜﻮن ﺣﻮﯾﺼﻠﺔ أو ﺗﺠﻤﻊ ﻣﻦ اﻟﺨﻼﯾﺎ ﺣﻮﻟﮫ ﻟﻮﻗﻒ ﺣﺮﻛﺘﮫ وﻣﻨﻊ اﻧﺘﺸﺎره ﻓﻲ اﻟﺪم وھﺬه اﻟﻌﻤﻠﯿﺔ ﺗﺴﻤﻰ اﻟﺘﺤﻮﺻﻞ ).(encapsulation ﺗﻐﺬﯾﺔ واﺳﺘﺰراع اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﺳﻠﻮك اﻟﺘﻐﺬﯾﺔ : اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﺣﯿﻮان ﻣﺘﻌﺪد اﻷﻏﺬﯾﺔ .....ﻓﮭﻮ ﯾﺘﻐﺬى ﻋﻠﻰ ﺑﻌﺾ اﻟﺤﯿﻮاﻧﺎت...ﻣﺜﻞ اﻷﺳﻤﺎك واﻟﻘﻮاﻗﻊ ،واﻟﻨﺒﺎﺗﺎت اﻟﻤﺎﺋﯿﺔ اﻟﻤﻐﻤﻮرة أو اﻟﺘﻲ ﺗﮭﺒﻂ إﻟﻰ اﻟﻘﺎع ﺣﯿﺚ ﻻ ﺗﺘﻤﻜﻦ اﻻﺳﺘﺎﻛﻮزا ﻣﻦ اﻟﺒﻘﺎء ﻃﻮﯾﻼً ﻋﻨﺪ ﺳﻄﺢ اﻟﻤﺎء ﻟﻜﻲ ﺗﺘﻐﺬى ﻋﻠﻰ اﻟﻨﺒﺎﺗﺎت اﻟﻄﺎﻓﯿﺔ. وﺑﺎﻟﻨﺴﺒﺔ ﻟﻠﻘﻮاﻗﻊ ﻓﺈن اﻻﺳﺘﺎﻛﻮزا ﺗﻠﺘﮭﻢ ﻣﺎ ﯾﻨﺎﺳﺒﮭﺎ ﻣﻨﮭﺎ ﺑﻨﺎءً ﻋﻠﻰ ﻋﺪة ﻋﻮاﻣﻞ؛ ﻣﺜﻞ ﺣﺠﻢ اﻟﻘﻮﻗﻊ ودرﺟﺔ ﺻﻼﺑﺔ اﻟﺼﺪﻓﺔ اﻟﺨﺎرﺟﯿﺔ ﻟﻠﻘﻮﻗﻊ ووﺟﻮد ﻏﻄﺎء اﻟﺼﺪﻓﺔ ﻣﻦ ﻋﺪﻣﮫ وﻗﺪرﺗﮭﺎ ﻋﻠﻰ اﻹﻣﺴﺎك ﺑﮭﺎ. وﯾﻌﺘﻤﺪ اﻓﺘﺮاس اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻟﻸﺳﻤﺎك ﻋﻠﻰ ﺳﮭﻮﻟﺔ اﻹﻣﺴﺎك ﺑﺎﻟﻔﺮﯾﺴﺔ ،ﺣﯿﺚ ﻣﻦ اﻟﺼﻌﺐ ﻋﻠﯿﮭﺎ اﻗﺘﻨﺎص اﻷﺳﻤﺎك اﻟﻤﺘﺤﺮﻛﺔ وھﻰ ﺣﯿﺔ ،وﻟﻜﻨﮭﺎ ﺗﻠﺘﮭﻢ اﻷﺳﻤﺎك اﻟﻨﺎﻓﻘﺔ ﻓﻘﻂ أو %10ﻣﻦ ﻣﺤﺘﻮى اﻟﻤﻌﺪة اﻟﻌﺎﺟﺰة ﻋﻦ اﻟﺤﺮﻛﺔ واﻟﮭﺮب ﻛﻤﺎ ﻓﻲ ﺷﺒﺎك اﻟﺼﯿﺪ .ﻛﻤﺎ وﺟﺪ أن ﻣﺼﺪره ﺣﯿﻮاﻧﻲ وﻛﺎﻧﺖ اﻟﻨﺒﺎﺗﺎت اﻟﺨﻀﺮاء ھﻲ اﻟﻤﺼﺪر اﻟﺜﺎﻧﻲ اﻟﻤﺴﺘﮭﻠﻚ. وﺗﻌﺘﻤﺪ ﺻﻐﺎر اﻻﺳﺘﺎﻛﻮزا ) 9 – 0.5و 1ﺳﻢ ﻃﻮل اﻟﺪرﻗﺔ( ﻓﻲ ﻏﺬاﺋﮭﺎ ﻋﻠﻰ اﻟﮭﺎﺋﻤﺎت اﻟﺤﯿﻮاﻧﯿﺔ، واﻟﺤﺠﻢ اﻟﻤﺘﻮﺳﻂ ) 4 .9 – 2ﺳﻢ ﻃﻮل اﻟﺪرﻗﺔ( ﯾﻔﻀﻞ اﻟﺤﯿﻮاﻧﺎت اﻟﺼﻐﯿﺮة ﻣﻊ اﻟﻨﺒﺎﺗﺎت ،أﻣﺎ اﻷﺣﺠﺎم اﻟﻜﺒﯿﺮة )ﻓﻮق 5ﺳﻢ ﻃﻮل اﻟﺪرﻗﺔ( ﻓﺘﻌﺘﻤﺪ ﻓﻲ ﻏﺬاﺋﮭﺎ ﻋﻠﻰ اﻷﺳﻤﺎك وﻏﯿﺮھﺎ ﻣﻦ اﻟﺤﯿﻮاﻧﺎت اﻟﻤﺎﺋﯿﺔ .وﯾﺮﺗﺒﻂ ﻗﻠﺔ اﻓﺘﺮاﺳﮭﺎ ﻟﻸﺳﻤﺎك اﻟﺤﯿﺔ ﺑﺴﺮﻋﺔ ﺣﺮﻛﺔ وھﺮوب اﻷﺳﻤﺎك .وﺗﻌﺘﻤﺪ 164
اﻟﺘﺮﺑﯿﺔ اﻻﻗﺘﺼﺎدﯾﺔ ﻷﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻋﻠﻰ اﻟﺘﻐﺬﯾﺔ اﻟﻄﺒﯿﻌﯿﺔ ﻣﻦ اﻟﻐﺬاء اﻟﻄﺒﯿﻌﻲ اﻟﻤﻮﺟﻮد ﻓﻲ اﻟﺒﯿﺌﺔ اﻟﻤﺤﯿﻄﺔ. اﻻﺣﺘﯿﺎﺟﺎت اﻟﻐﺬاﺋﯿﺔ : ﺗﺸﺒﮫ اﻻﺣﺘﯿﺎﺟﺎت اﻟﻐﺬاﺋﯿﺔ ﻷﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻓﻲ اﻟﻨﻈﺎم اﻟﻤﻐﻠﻖ ﻣﺎ ﺗﺤﺘﺎﺟﮫ أﺳﻤﺎك اﻟﻘﺮﻣﻮط ﻓﻲ ﺗﻐﺬﯾﺘﮭﺎ .وﻓﻰ اﻟﺘﺠﺎرب اﻟﻤﻌﻤﻠﯿﺔ )ﺑﺪون ﻏﺬاء ﻃﺒﯿﻌﻲ( وﺟﺪ أن ھﺎ ﺗﺤﺘﺎج إﻟﻰ ﻋﻼﺋﻖ ﺻﻨﺎﻋﯿﺔ ﺗﺤﺘﻮى ﻣﻦ 20إﻟﻰ %30ﺑﺮوﺗﯿﻦ وأن %20 -15ﻣﻦ اﻟﺒﺮوﺗﯿﻦ ﯾﻜﻮن ﺣﯿﻮاﻧﻲ اﻟﻤﺼﺪر وأﯾﻀﺎً اﻟﻄﺎﻗﺔ ﺣﻮاﻟﻲ 2500ﻛﯿﻠﻮ ﻛﺎﻟﻮرى /ﻛﯿﻠﻮﺟﺮام وزن اﻟﺠﺴﻢ ﻟﯿﻌﻄﻰ أﻋﻠﻰ ﻧﻤﻮ وﺗﺮاﻛﻢ ﺑﺮوﺗﯿﻦ. اﻻﺳﺘﺰراع و اﻟﺘﺮﺑﯿﺔ : ﯾﻤﻜﻦ أن ﺗﺮﺑﻰ أو ﺗﺴﺘﺰرع اﻻﺳﺘﺎﻛﻮزا ﻓﻲ أﺣﻮاض ﻛﺒﯿﺮة ،ﺣﯿﺚ ﯾﻮﺟﺪ ﻧﻮﻋﺎن ﻣﻨﮭﺎ ؛ أﺣﻮاض ﻣﻔﺘﻮﺣﺔ أو أﺣﻮاض ﻣﻐﻄﺎة ﺑﺎﻟﻨﺒﺎت .اﻷﺣﻮاض اﻟﻤﻔﺘﻮﺣﺔ ﯾﻐﻠﺐ ﻋﻠﯿﮭﺎ اﻟﻨﺒﺎﺗﺎت اﻟﻤﺎﺋﯿﺔ ،وﯾﻤﻜﻦ أن ﯾﺘﻢ ذﻟﻚ ﻓﻲ ﻣﺰارع اﻷرز ﻣﻊ ﺑﻌﺾ اﻷﻋﺸﺎب اﻟﻤﺎﺋﯿﺔ .أﻣﺎ اﻷﺣﻮاض اﻟﻤﺸﺠﺮة ﻓﺘﺤﺘﻮى ﻣﺠﻤﻮﻋﺔ ﻣﻦ اﻟﺸﺠﯿﺮات واﻷﺷﺠﺎر .وﺗﺼﻤﻢ اﻷﺣﻮاض اﻟﻤﺨﺼﺼﺔ ﻟﺘﺮﺑﯿﺔ اﻻﺳﺘﺎﻛﻮزا ﻓﻲ أﺣﻮاض ﻃﯿﻨﯿﺔ ﺗﺨﺘﻠﻒ ﻓﻲ اﻟﻤﺴﺎﺣﺔ ﺑﺤﯿﺚ ﯾﻜﻮن ارﺗﻔﺎع اﻟﻤﺎء ﺑﮭﺎ ﺣﻮاﻟﻲ 30إﻟﻰ 75ﺳﻢ. وﻗﺪ ﺗﺴﺒﺐ وﺟﻮد اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻓﻲ ﺧﺰاﻧﺎت وﻗﻨﻮات اﻟﺮي وﻓﻰ ﺣﻘﻮل اﻷرز ﻓﻲ ﻇﮭﻮر ﺑﻌﺾ اﻟﻤﺸﺎﻛﻞ ﻓﻲ زراﻋﺔ اﻷرز ﺑﺴﺒﺐ اﻟﺘﻨﻘﯿﺐ وﺗﻌﺪد ﻇﺮوف ﺗﻐﺬﯾﺘﮭﺎ .ﻛﻤﺎ ﯾﺴﺒﺐ ﺗﻨﻘﯿﺐ أو ﺣﻔﺮ اﻷﻧﻔﺎق ﻓﻘﺪا ﻓﻲ اﻟﻤﺎء ﻣﻦ اﻟﺨﺰاﻧﺎت وﺣﻘﻮل اﻷرز وﺑﺎﻟﺘﺎﻟﻲ ﯾﻘﻞ إﻧﺘﺎج اﻷرز .وﻓﻰ ﺑﻌﺾ ﺣﻘﻮل اﻷرز ﯾﺴﺘﺨﺪم اﻟﻤﺰارﻋﻮن ﻣﺒﯿﺪات ﺣﺸﺮﯾﺔ ﻟﻠﺘﺤﻜﻢ ﻓﻲ ﺗﻜﺎﺛﺮ اﻻﺳﺘﺎﻛﻮزا ،ﻣﻤﺎ ﯾﺆدى إﻟﻰ ﺗﻠﻮث اﻟﻤﯿﺎه واﻟﺒﯿﺌﺔ ﻋﺎﻣﺔ. وﯾﺒﺪأ ﻣﻮﺳﻢ اﺳﺘﺰراع اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻓﻲ ﻣﻌﻈﻢ اﻟﺪول اﻟﺘﻲ ﺗﺴﺘﺰرﻋﮫ ﻣﻦ ﻧﺼﻒ أﺑﺮﯾﻞ إﻟﻰ آﺧﺮه ،وﯾﺨﺘﻠﻒ ﻣﻌﺪل اﻟﺘﺨﺰﯾﻦ ﻣﻦ 22إﻟﻰ 28ﻛﯿﻠﻮ/ھﻜﺘﺎر ﻣﻊ ﺗﻮاﻓﺮ اﻟﻨﺒﺎﺗﺎت أو ﻣﻦ 65 إﻟﻰ 112ﻛﯿﻠﻮ/ھﻜﺘﺎر ﻓﻲ أﺣﻮاض ﺑﺪون ﻧﺒﺎﺗﺎت .وﺗﺨﺰن اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ اﻟﻨﺎﺿﺠﺔ ﺑﻨﺴﺒﺔ 1:1ﻣﻦ اﻟﺠﻨﺴﯿﻦ. وﺗﺘﺰاﻣﻦ اﻟﻔﺘﺮة ﻣﻦ ﻣﻨﺘﺼﻒ ﺳﺒﺘﻤﺒﺮ إﻟﻰ أواﺧﺮ ﻧﻮﻓﻤﺒﺮ ﻣﻊ إﻧﺘﺎج اﻟﺒﯿﺾ ﻟﻺﻧﺎث وﻣﻦ أھﻢ اﻟﻌﻮاﻣﻞ اﻟﺘﻲ ﺗﺆﺛﺮ ﻋﻠﻰ إﻧﺘﺎج اﻟﺰرﯾﻌﺔ ھﻲ ﻣﻮاﺻﻔﺎت اﻟﻤﯿﺎه وأھﻤﮭﺎ ﺗﺮﻛﯿﺰ اﻷﻛﺴﺠﯿﻦ اﻟﺬاﺋﺐ ﺣﯿﺚ ﯾﺰداد ﻋﺪد اﻟﻮﻓﯿﺎت وﯾﻘﻞ اﻟﻨﻤﻮ ﺑﺴﺒﺐ ﻗﻠﺔ اﻷﻛﺴﺠﯿﻦ اﻟﺬاﺋﺐ ﻓﻲ اﻟﻤﺎء إﻟﻰ أﻗﻞ ﻣﻦ 1ﺟﺰء ﻓﻲ اﻟﻤﻠﯿﻮن ،وﻟﺬا ﯾﺠﺐ أن ﻻ ﯾﻘﻞ ﻋﻦ 3ﺟﺰء ﻓﻲ اﻟﻤﻠﯿﻮن .وﻣﻦ اﻟﻌﻮاﻣﻞ اﻟﺘﻲ ﻧﺤﺎﻓﻆ ﻋﻠﻰ اﻷﻛﺴﺠﯿﻦ اﻟﺬاﺋﺐ ﻓﻲ اﻟﻤﺎء ﺗﻮﻓﯿﺮ ﻛﻤﯿﺔ ﻣﻦ اﻟﻨﺒﺎﺗﺎت أو اﺳﺘﺨﺪام اﻟﺘﮭﻮﯾﺔ اﻟﺼﻨﺎﻋﯿﺔ ﻣﻊ ﺗﻐﯿﺮ اﻟﻤﯿﺎه. اﻷھﻤﯿﺔ اﻻﻗﺘﺼﺎدﯾﺔ ودرﺟﺔ اﻷﻣﺎن اﻟﺒﯿﻮﻟﻮﺟﻲ ﻟﻤﻌﺮﻓﺔ ﻗﯿﻤﺘﮫ اﻻﻗﺘﺼﺎدﯾﺔ ﻋﻨﺪ اﺳﺘﻐﻼﻟﮫ ﻛﻐﺬاء آﻣﻦ ،ﺗﻢ ﺗﻘﯿﯿﻢ دﻗﯿﻖ ﻷﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻛﻤﺼﺪر ﻏﺬاﺋﻲ ﺟﯿﺪ ورﺧﯿﺺ اﻟﺜﻤﻦ ﻟﻺﻧﺴﺎن ﻣﻘﺎرﻧﺔ ﺑﺎﻟﺠﻤﺒﺮي اﻟﺒﺤﺮي ﻓﻲ ﻣﺼﺮ ،ﻓﻘﺪ ﺟﻤﻌﺖ ﻋﯿﻨﺎت ﻣﻦ ذﻛﻮر وإﻧﺎث اﻻﺳﺘﺎﻛﻮزا ﻣﻦ ﻧﮭﺮ اﻟﻨﯿﻞ ﻋﻨﺪ اﻟﻘﺎھﺮة ﻟﻤﻘﺎرﻧﺘﮭﺎ ﺑﻌﯿﻨﺎت ﻧﻮﻋﯿﻦ ﻣﻦ 165
ﺟﻤﺒﺮي اﻟﻤﯿﺎه اﻟﻤﺎﻟﺤﺔ؛ أﺣﺪھﻤﺎ اﻟﺠﻤﺒﺮي اﻟﯿﺎﺑﺎﻧﻲ اﻟﺬي ﺟﻤﻊ ﻣﻦ ﺑﺤﯿﺮة ﻗﺎرون و اﻟﺜﺎﻧﻲ اﻟﺠﻤﺒﺮي اﻟﺴﻮﯾﺴﻲ اﻟﺬي ﺟﻤﻊ ﻣﻦ ﺧﻠﯿﺞ اﻟﺴﻮﯾﺲ.وﻗﺪ أوﺿﺤﺖ ﻧﺘﺎﺋﺞ ﺗﻘﻨﯿﺔ اﻟﺤﻤﻞ اﻟﻜﮭﺮﺑﻲ ﻟﺒﺮوﺗﯿﻨﺎت اﻟﻠﺤﻢ ﺗﺸﺎﺑﮭﺎ ﺑﯿﻦ اﻻﺳﺘﺎﻛﻮزا و اﻟﺠﻤﺒﺮي اﻟﺴﻮﯾﺴﻲ ﻋﻼوة ﻋﻠﻲ اﻟﺘﺸﺎﺑﮫ ﻓﻲ اﻟﺘﺮﻛﯿﺐ اﻟﻜﯿﻤﯿﺎﺋﻲ و ﻣﺤﺘﻮى اﻟﺒﺮوﺗﯿﻦ اﻟﻜﻠﻲ و اﻟﻔﻮﺳﻔﻮر و اﻟﻜﺎﻟﺴﯿﻮم و اﻟﺴﯿﻠﯿﻨﯿﻮم و اﻟﺰﻧﻚ ﺑﺎﻹﺿﺎﻓﺔ إﻟﻲ ﻓﯿﺘﺎﻣﯿﻨﺎت ب ، 1ب 2و ب. 5 وﻣﻊ ﺗﻨﻮع ﺑﯿﺌﺔ اﻟﻘﺸﺮﯾﺎت اﻟﺘﻲ ﺗﻢ دراﺳﺘﮭﺎ ﻣﻦ ﺑﯿﺌﺔ ﻣﯿﺎه ﻋﺬﺑﺔ ﻟﻸﺳﺘﺎﻛﻮزا إﻟﻰ ﻣﯿﺎه ﻣﺎﻟﺤﺔ ﻟﻠﺠﻤﺒﺮي اﻟﯿﺎﺑﺎﻧﻲ و اﻟﺴﻮﯾﺴﻲ ،و ﺑﺎﻟﺮﻏﻢ ﻣﻦ ﺗﺸﺎﺑﮫ ﻣﯿﺎه ﻣﻨﺎﻃﻖ ﺗﺠﻤﯿﻊ اﻟﻘﺸﺮﯾﺎت ﻓﻲ ﺗﺮﻛﯿﺰات اﻟﻌﻨﺎﺻﺮ اﻟﺜﻘﯿﻠﺔ )ﺣﺪﯾﺪ ،ﻧﺤﺎس ،رﺻﺎص ،زﻧﻚ ،ﻣﻨﺠﻨﯿﺰ و ﻛﺎدﻣﯿﻮم( ،إﻻ أﻧﮭﺎ ﺗﺮاﻛﻤﺖ ﺑﻨﺴﺐ وﺑﻨﺴﺐ ﻣﺴﻤﻮح ﺑﮭﺎ ﻣﻘﺎرﻧﺔ ﺑﻨﻮﻋﻲ اﻟﺠﻤﺒﺮي اﻗﻞ ﻓﻲ ﻋﻀﻼت اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ اﻟﻤﺬﻛﻮرﯾﻦ. ﻟﺬا أوﺻﺖ ﻣﻌﻈﻢ اﻟﺪراﺳﺎت اﻟﺘﺤﻠﯿﻠﯿﺔ ﺑﺎﺳﺘﺨﺪام اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻛﻤﺼﺪر ﻟﻠﺒﺮوﺗﯿﻦ اﻟﺤﯿﻮاﻧﻲ ﺑﺄﻧﮫ ﻏﺬاء ﻣﺘﻜﺎﻣﻞ ﺻﺤﻲ و آﻣﻦ ﻟﻺﻧﺴﺎن ﻣﻘﺎرﻧﺔ ﺑﺠﻤﺒﺮي اﻟﻤﯿﺎه اﻟﻤﺎﻟﺤﺔ اﻟﻤﺮﺗﻔﻊ اﻟﺜﻤﻦ .وإﻟﻲ ﺟﺎﻧﺐ ذﻟﻚ ﺗﺄﺗﻲ اﻷھﻤﯿﺔ اﻻﻗﺘﺼﺎدﯾﺔ ﻟﻠﻘﺸﺮة اﻟﻤﺘﺒﻘﯿﺔ ﻣﻦ اﻟﺤﯿﻮان )و ﺗﺸﻤﻞ اﻟﮭﯿﻜﻞ اﻟﺨﺎرﺟﻲ واﻷﺟﺰاء ﻏﯿﺮ اﻟﻘﺎﺑﻠﺔ ﻟﻠﺘﻐﺬﯾﺔ( و ﯾﻤﻜﻦ اﺳﺘﺨﺪاﻣﮭﺎ ﻛﺴﻤﺎد أو ﻛﻌﻠﻒ ﻟﻠﻄﯿﻮر واﻷﺳﻤﺎك. ﺣﯿﺚ ﺑﯿﻨﺖ ﻧﺘﺎﺋﺞ اﻟﺘﺤﻠﯿﻼت اﻟﻜﯿﻤﯿﺎﺋﯿﺔ أن اﻟﻘﺸﺮة اﻟﻤﺘﺒﻘﯿﺔ ﻣﻦ اﻟﺤﯿﻮان ﺗﺤﺘﻮي ﻋﻠﻰ ﻧﺴﺒﺔ ﻋﺎﻟﯿﺔ ﻣﻦ اﻟﺒﺮوﺗﯿﻦ و ﻣﺤﺘﻮى دھﻨﻲ ﻣﻨﺨﻔﺾ ﻣﻊ ﻧﺴﺒﺔ ﻋﺎﻟﯿﺔ ﻣﻦ اﻟﺮﻣﺎد اﻟﺬي ﯾﺤﻮي ﺑﻌﺾ اﻟﻤﻌﺎدن ﻣﺜﻞ اﻟﻜﺎﻟﺴﯿﻮم ،اﻟﻔﺴﻔﻮر ،اﻟﻤﺎﻏﻨﺴﯿﻮم ،اﻟﻤﻨﺠﻨﯿﺰ ،اﻟﺒﻮﺗﺎﺳﯿﻮم ،اﻟﺼﻮدﯾﻮم و اﻟﺤﺪﯾﺪ .ھﺬا و ﺗﻢ ﻣﻌﺎﻟﺠﺔ ﻗﺸﺮة اﻟﺤﯿﻮان ﺑﻌﺪ ﺣﺮﻗﮭﺎ ﻣﻤﺎ أدى إﻟﻰ ﺗﻘﻠﯿﻞ ﻧﺴﺒﺔ اﻟﺮﻣﺎد و ﺟﻌﻞ اﻟﻘﺸﺮة ذات ﻗﯿﻤﺔ ﻏﺬاﺋﯿﺔ ﻋﺎﻟﯿﺔ . وﻟﺘﺤﻘﯿﻖ اﻻﺳﺘﻔﺎدة ﻣﻦ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﺗﻢ اﻟﺤﺼﻮل ﻋﻠﻰ ﻣﻨﺘﺠﺎت ﻏﺬاﺋﯿﺔ وأﺧﺮى ﺗﺠﺎرﯾﺔ ﻣﻦ ھﺬا اﻟﺤﯿﻮان .ﯾﺸﻤﻞ اﻟﻤﻨﺘﺞ اﻷول )اﻟﻐﺬاﺋﻲ( ﻣﺠﻤﻞ اﻟﺤﯿﻮان اﻟﺤﻲ ﺳﻮاء ﻛﺎن ﺻﻐﯿﺮاً أو ﻛﺒﯿﺮ اﻟﺤﺠﻢ و ﻛﺬﻟﻚ اﻟﺤﯿﻮان اﻟﺴﻠﯿﻢ اﻟﻤﺜﻠﺞ )إﻣﺎ ﺳﺒﻖ ﻏﻠﯿﮫ أو ﻏﯿﺮ ﻣﻄﮭﻲ( .أﻣﺎ اﻟﻤﻨﺘﺠﺎت اﻟﺘﺠﺎرﯾﺔ ﻓﻘﺪ ﺗﻢ ﺗﺼﻨﯿﻔﮭﺎ إﻟﻰ ﺛﻼﺛﺔ ﻋﻨﺎﺻﺮ ،اﻷول ﯾﺸﻤﻞ اﻟﺤﯿﻮاﻧﺎت اﻟﺼﻐﯿﺮة )اﻟﺤﯿﺔ( اﻟﺘﻲ ﯾﻤﻜﻦ أن ﺗﺒﺎع ﻛﻄﻌﻢ ﻟﻠﺴﻤﻚ ،اﻟﺜﺎﻧﻲ اﺳﺘﺨﺪام اﻟﺤﯿﻮان ﻛﻨﻤﺎذج ﺑﯿﻮﻟﻮﺟﯿﺔ ﻓﻲ اﻟﻤﻌﺎﻣﻞ ﻟﻸﻏﺮاض اﻟﺒﺤﺜﯿﺔ واﻟﺘﺸﺮﯾﺤﯿﺔ ،أﻣﺎ اﻟﺜﺎﻟﺚ ﻓﮫي ﻧﻮاﺗﺞ اﻟﻘﺸﺮة اﻟﻤﺘﺒﻘﯿﺔ ﻣﻦ اﻟﺤﯿﻮان. وﯾﻤﻜﻦ ﺗﺴﻮﯾﻖ ھﺬا اﻟﺤﯿﻮان ﺑﺎﻷﺣﺠﺎم اﻟﻜﺒﯿﺮة ﻣﻦ ﺧﻼل ﺛﻼث ﻗﻨﻮات ﻟﻠﺘﻮزﯾﻊ :اﻷوﻟﻲ ھﻲ أﺳﻮاق اﻷﻏﺬﯾﺔ اﻟﺒﺤﺮﯾﺔ و ﻣﻨﮭﺎ إﻟﻰ اﻟﻤﺴﺘﮭﻠﻚ ،و اﻟﺜﺎﻧﯿﺔ اﻟﻤﻄﺎﻋﻢ و ﻣﻨﮭﺎ أﯾﻀﺎ إﻟﻰ اﻟﻤﺴﺘﮭﻠﻚ واﻟﺜﺎﻟﺜﺔ ھﻲ اﻟﺘﺼﺪﯾﺮ ﺣﯿﺔ إﻟﻰ اﻷﺳﻮاق اﻟﺨﺎرﺟﯿﺔ .ﺣﯿﺚ ﺗﺴﺘﻄﯿﻊ اﻻﺳﺘﺎﻛﻮزا اﻟﺒﻘﺎء ﺧﺎرج اﻟﻤﺎء ﻟﻌﺪة أﯾﺎم ﻣﻤﺎ ﯾﺴﮭﻞ ﺗﺠﮭﯿﺰھﺎ ﻓﻲ أﻛﯿﺎس ﻣﻦ اﻟﺨﯿﺶ وﻧﻘﻠﮭﺎ إﻟﻰ اﻟﺨﺎرج ﻟﻸﺳﻮاق اﻟﺘﻲ ﺗﺘﮭﺎﻓﺖ ﻋﻠﻰ ﺷﺮاﺋﮭﺎ.
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وﻟﺪراﺳﺔ ﻗﺪرة اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ اﻟﻤﻮﺟﻮدة ﻓﻲ اﻟﻨﯿﻞ ﻋﻠﻰ ﺗﺤﻤﻞ ﺑﻌﺾ اﻟﻌﻨﺎﺻﺮ اﻟﺜﻘﯿﻠﺔ اﻟﺘﻲ ﻗﺪ ﺗﻮﺟﺪ ﻓﯿﮫ ﻧﺘﯿﺠﺔ اﻟﺘﻠﻮث ،و دراﺳﺔ ﻣﺪى ﺻﻼﺣﯿﺘﮭﺎ ﻛﻐﺬاء ﻟﻺﻧﺴﺎن ﻓﻘﺪ ﺗﻢ اﺧﺘﯿﺎر أرﺑﻊ ﻣﻨﺎﻃﻖ ﻣﺨﺘﻠﻔﺔ ﻣﻦ ﻧﮭﺮ اﻟﻨﯿﻞ و ھﻲ ﻣﻨﻄﻘﺔ أﺑﻮ ﻛﺒﯿﺮ ﺑﻤﺤﺎﻓﻈﺔ اﻟﺸﺮﻗﯿﺔ وﻣﻨﻄﻘﺔ ﺣﻠﻮان ﺑﺠﻮار اﻟﻘﺎھﺮة و ﻣﻨﻄﻘﺔ اﻟﻔﯿﻮم و ﻣﻨﻄﻘﺔ أﺑﻮ رواش ﺑﻤﺤﺎﻓﻈﺔ اﻟﺠﯿﺰة ،و ﺗﻢ ﺟﻤﻊ ﻋﯿﻨﺎت ﻣﻦ اﻻﺳﺘﺎﻛﻮزا ﻣﻦ ﺗﻠﻚ اﻟﻤﻨﺎﻃﻖ .و ﻗﺪ اﺧﺘﯿﺮت أﻋﻀﺎء ﻣﺨﺘﻠﻔﺔ ﻣﻦ اﻟﺤﯿﻮان ﻟﺪراﺳﺔ ﺗﺮاﻛﻢ اﻟﻌﻨﺎﺻﺮ اﻟﺜﻘﯿﻠﺔ ﺑﺪاﺧﻠﮭﺎ و ھﻲ : .١اﻟﺨﯿﺎﺷﯿﻢ :ﺑﺎﻋﺘﺒﺎرھﺎ اﻟﮭﺪف اﻷول ﻟﺪﺧﻮل اﻟﻌﻨﺎﺻﺮ اﻟﺜﻘﯿﻠﺔ ﻟﺠﺴﻢ اﻟﺤﯿﻮان )ﺳﻮاء وذﻟﻚ ﻟﻮﺟﻮد ﻛﺎﻧﺖ ھﺬه اﻟﻌﻨﺎﺻﺮ ﻣﻮﺟﻮدة ﻓﻲ اﻟﻤﯿﺎه أو ﻓﻲ اﻟﺘﺮﺑﺔ اﻟﻤﺤﯿﻄﺔ ﺑﮫ ﺧﺎﺻﯿﺔ ﺣﻔﺮ اﻷﻧﻔﺎق ﻓﻲ ھﺬه اﻻﺳﺘﺎﻛﻮزا( . .٢اﻟﻐﺪة اﻟﮭﺎﺿﻤﺔ أو اﻟﻜﺒﺪﺑﻨﻜﺮﯾﺎس :و ﺗﻌﺘﺒﺮ أھﻢ وأﻛﺒﺮ ﻏﺪة ﻓﻲ اﻟﺤﯿﻮان وﺗﻘﻮم ﺑﻌﻤﻞ اﻟﻜﺒﺪ و اﻟﺒﻨﻜﺮﯾﺎس ﻓﻲ اﻟﺤﯿﻮاﻧﺎت اﻷﺧﺮى . .٣اﻟﻐﺪة اﻹﺧﺮاﺟﯿﺔ أو اﻟﺰﺑﺎﻧﯿﺔ اﻟﺨﻀﺮاء :و ھﻲ أﺻﻐﺮ و ﺛﺎﻧﻲ ﻏﺪة ﻓﻲ اﻟﺤﯿﻮان وﻟﮭﺎ أھﻤﯿﺔ اﻟﻜﻠﯿﺔ ﻓﻲ اﻟﻔﻘﺎرﯾﺎت وﺗﻮﺟﺪ ﻓﻲ ﻗﺎﻋﺪة ﻗﺮﻧﻲ اﻻﺳﺘﺸﻌﺎر. .٤اﻟﻌﻀﻼت اﻟﺒﻄﻨﯿﺔ :ﺑﺎﻋﺘﺒﺎرھﺎ أھﻢ ﺟﺰء ﻓﻲ ﺟﺴﻢ اﻟﺤﯿﻮان واﻟﺬي ﯾﻤﻜﻦ اﻻﺳﺘﻔﺎدة ﻣﻨﮫ ﻛﻐﺬاء ﻟﻺﻧﺴﺎن. ﻛﻤﺎ اﺧﺘﯿﺮت أرﺑﻌﺔ ﻋﻨﺎﺻﺮ ﺛﻘﯿﻠﺔ ﻟﺪراﺳﺔ ﺗﺮاﻛﻤﮭﺎ ﺑﺄﺟﺴﺎم اﻻﺳﺘﺎﻛﻮزا اﻟﻤﺠﻤﻌﺔ ﻣﻦ ﻣﻨﺎﻃﻖ اﻟﺪراﺳﺔ اﻟﻤﺨﺘﻠﻔﺔ و ھﻲ اﻟﻨﺤﺎس واﻟﺰﻧﻚ واﻟﺮﺻﺎص واﻟﻜﺎدﻣﯿﻮم .وﺗﻢ أﯾﻀﺎ دراﺳﺔ ﻧﻮﻋﯿﺔ اﻟﻤﯿﺎه و ﺗﺮﻛﯿﺰ ﻛﻞ ﻣﻦ ھﺬه اﻟﻌﻨﺎﺻﺮ ﻓﯿﮭﺎ .وأﻇﮭﺮت اﻟﻨﺘﺎﺋﺞ أﻋﻠﻰ درﺟﺔ ﻣﻦ ﻋﺴﺮ اﻟﻤﯿﺎه وﻣﻦ اﻟﻤﻠﻮﺣﺔ ﻓﻲ ﻣﻨﻄﻘﺔ اﻟﻔﯿﻮم ،ﻣﻤﺎ ﯾﺆﻛﺪ ﻗﺪرة ھﺬا اﻟﺤﯿﻮان ﻋﻠﻰ ﺗﺤﻤﻞ ھﺬه اﻟﻤﻠﻮﺣﺔ اﻟﻌﺎﻟﯿﺔ وﯾﻔﺴﺮ اﻧﺘﺸﺎر ھﺬا اﻟﺤﯿﻮان ﺑﺼﻮرة ﻛﺒﯿﺮة ﻓﻲ ﻣﺤﺎﻓﻈﺔ اﻟﻔﯿﻮم. ﻛﻤﺎ أﺛﺒﺘﺖ اﻟﻨﺘﺎﺋﺞ أن أﻋﻠﻲ ﺗﺮﻛﯿﺰ ﻟﻠﻨﺤﺎس و اﻟﺰﻧﻚ ﻛﺎن ﻓﻲ اﻟﻐﺪة اﻟﺰﺑﺎﻧﯿﺔ أو اﻟﺨﻀﺮاء ﻹﻧﺎث اﻻﺳﺘﺎﻛﻮزا .و ﯾﻤﻜﻦ إرﺟﺎع ذﻟﻚ إﻟﻰ ﻗﺪرة اﻹﻧﺎث ﻋﻠﻰ اﻟﺘﺨﻠﺺ ﻣﻦ اﻟﻤﻠﻮﺛﺎت أﺳﺮع ﻣﻦ اﻟﺬﻛﻮر .أﻣﺎ ﺑﺎﻟﻨﺴﺒﺔ ﻟﺘﺮاﻛﻢ ﻛﻞ ﻣﻦ ﻋﻨﺼﺮي اﻟﺮﺻﺎص و اﻟﻜﺎدﻣﯿﻮم ﻓﻲ ذﻛﻮر و إﻧﺎث اﻻﺳﺘﺎﻛﻮزا ﻓﻜﺎﻧﺎ ﺑﺄﻋﻠﻰ ﻗﯿﻢ ﻓﻲ اﻟﻐﺪة اﻟﺰﺑﺎﻧﯿﺔ ﻓﻲ اﻟﻌﯿﻨﺎت اﻟﺘﻲ ﺟﻤﻌﺖ ﻣﻦ ﺟﻤﯿﻊ ﻣﻨﺎﻃﻖ اﻟﺪراﺳﺔ .ﻣﻤﺎ ﯾﻔﺴﺮ أھﻤﯿﺔ ھﺬه اﻟﻐﺪة و أﻧﮭﺎ ﺗﻠﻌﺐ دورا ﻛﺒﯿﺮا ﻓﻲ اﻟﺘﺨﻠﺺ ﻣﻦ اﻟﻤﻠﻮﺛﺎت. و ﺑﺬﻟﻚ ﯾﺘﻀﺢ أن اﻻﺳﺘﺎﻛﻮزا اﻟﺤﻤﺮاء ﺑﺮوﻛﻤﺒﺎرس ﻛﻼرﻛﻲ ﻟﮭﺎ اﻟﻘﺪرة ﻋﻠﻰ اﻟﺘﻌﺎﯾﺶ ﻓﻲ ﻣﻨﺎﻃﻖ ﺑﯿﺌﯿﺔ ﻣﻠﻮﺛﺔ ﺑﺎﻟﻌﻨﺎﺻﺮ اﻟﺜﻘﯿﻠﺔ ،ﻛﻤﺎ أن ﻟﮭﺎ اﻟﻘﺪرة ﻋﻠﻰ ﺗﺮاﻛﻢ ﺗﻠﻚ اﻟﻌﻨﺎﺻﺮ ﻓﻲ ﺑﻌﺾ أﻋﻀﺎﺋﮭﺎ ﺧﺼﻮﺻﺎ اﻟﻐﺪة اﻟﺨﻀﺮاء اﻹﺧﺮاﺟﯿﺔ ،واﻟﺘﻲ أﻇﮭﺮت اﻟﻨﺘﺎﺋﺞ أﻧﮭﺎ ﺗﻠﻌﺐ دورا ﻛﺒﯿﺮا ﻓﻲ اﻟﺘﺨﻠﺺ ﻣﻦ اﻟﻤﻠﻮﺛﺎت ،ﻣﻤﺎ ﯾﻌﻨﻲ إﻣﻜﺎﻧﯿﺔ اﺳﺘﺨﺪام ھﺬا اﻟﺤﯿﻮان ﻛﺪﻟﯿﻞ ﺑﯿﻮﻟﻮﺟﻲ ) (bioindicator ﻟﻠﺘﻌﺮف ﻋﻠﻰ اﻟﻤﻨﺎﻃﻖ اﻟﻤﺎﺋﯿﺔ اﻟﻤﻠﻮﺛﺔ ﺑﺎﻟﻌﻨﺎﺻﺮ اﻟﺜﻘﯿﻠﺔ ﻛﻤﺎ اﺗﻀﺢ ﻓﻲ ﻣﻨﺎﻃﻖ اﻟﺪراﺳﺔ اﻟﻤﺨﺘﻠﻔﺔ .
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واﻟﺨﻼﺻﺔ إن اﻟﺒﺤﻮث ﺗﺆﻛﺪ ﺳﻼﻣﺔ اﻻﻋﺘﻤﺎد ﻋﻠﻰ ھﺬا اﻟﺤﯿﻮان اﻟﻘﺸﺮي ﺳﺮﯾﻊ اﻻﻧﺘﺸﺎر ﻛﻐﺬاء ﺑﺮوﺗﯿﻨﻲ رﺧﯿﺺ ﻋﻠﻰ أن ﯾﺘﻢ ﺻﯿﺪه ﻣﻦ ﻣﻨﺎﻃﻖ اﻟﻤﯿﺎه ﻏﯿﺮ اﻟﻤﻠﻮﺛﺔ أو ﻣﻦ اﻟﻤﺰارع اﻟﺨﺎﺻﺔ .ﻣﻊ اﺳﺘﺨﺪام ﺑﻘﺎﯾﺎ اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ اﻟﺘﻲ ﻻ ﺗﺆﻛﻞ ﻓﻲ ﺗﺼﻨﯿﻊ ﻋﻠﻒ اﻟﺤﯿﻮاﻧﺎت. وﻓﻰ ﻣﺤﺎوﻟﺔ ﻟﻼﺳﺘﻔﺎدة ﻣﻦ ھﺬا اﻟﺤﯿﻮان ﻓﻲ ﻣﺼﺮ ،ﺗﻢ دراﺳﺔ إﻣﻜﺎﻧﯿﺔ اﺳﺘﺰراﻋﮫ ﻓﻲ أﻣﺎﻛﻦ ﺑﻌﯿﺪة ﻋﻦ وادي اﻟﻨﯿﻞ ،واﺳﺘﻐﻼل اﻟﺠﺰء اﻟﺬي ﻻ ﯾﺆﻛﻞ ﻣﻨﮫ ﻓﻲ إﻧﺘﺎج ﻋﻠﻒ ﺣﯿﻮاﻧﻲ ﻟﻠﺪواﺟﻦ أو ﻋﻼﺋﻖ ﻟﻠﻤﺰارع اﻟﺴﻤﻜﯿﺔ .وﻗﺪ ﺧﻠﺼﺖ ھﺬه اﻟﺪراﺳﺔ إﻟﻰ ﻣﺎ ﯾﺄﺗﻲ: -1ﯾﻤﻜﻦ اﺳﺘﺰراع اﺳﺘﺎﻛﻮزا اﻟﻤﯿﺎه اﻟﻌﺬﺑﺔ ﻓﻲ ﻣﺼﺮ ،ﻣﻊ ﺗﻮﻓﯿﺮ اﻟﻈﺮوف اﻟﻤﻼﺋﻤﺔ ﻣﻦ ﺣﯿﺚ ﻛﺜﺎﻓﺔ اﻷﻓﺮاد اﻟﻤﻮﺟﻮدة ﻓﻲ ﻣﺴﺎﺣﺔ ﻣﻌﯿﻨﺔ ﯾﺘﻮاﻓﺮ ﺑﮭﺎ إﻣﻜﺎﻧﯿﺔ ﺣﻔﺮ أﻧﻔﺎق ﺟﺎﻧﺒﯿﺔ ﺗﺴﺘﻄﯿﻊ ﻣﻦ ﺧﻼﻟﮭﺎ اﻻﺧﺘﺒﺎء واﻟﺤﻤﺎﯾﺔ ﻣﻦ اﻟﮭﺠﻮم ﻋﻠﯿﮭﺎ ﻣﻦ اﻷﻧﻮاع اﻷﺧﺮى إﻟﻰ ﺟﺎﻧﺐ ﻣﺮاﻋﺎة ﻧﺴﺒﺔ اﻟﺬﻛﻮر ﻟﻺﻧﺎث ﻣﻊ ﻗﻮة و ﺳﻼﻣﺔ اﻷﻓﺮاد و أﺣﺠﺎم اﻷﻓﺮاد اﻟﺘﻲ ﺗﻮﺿﻊ ﻣﻌﺎ ﻓﻲ ﻣﻜﺎن واﺣﺪ وﻛﺬﻟﻚ ﺗﻮاﺟﺪ ﻣﺮاﺣﻞ ﻋﻤﺮﯾﺔ ﻣﺘﻘﺎرﺑﺔ ﻟﻸﻓﺮاد و درﺟﺔ ﺣﺮارة ﻣﻼﺋﻤﺔ وﻋﻤﻖ ﻣﻨﺎﺳﺐ ﻣﻦ اﻟﻤﺎء وﺗﻮاﻓﺮ ﺧﻠﯿﻂ ﻣﻦ ﻏﺬاء ﻧﺒﺎﺗﻲ و ﺣﯿﻮاﻧﻲ وﺣﺠﻢ اﻟﻐﺬاء اﻟﻤﻨﺎﺳﺐ ﻟﻌﺪد اﻷﻓﺮاد .ﻛﻤﺎ ﯾﻠﺰم ﻣﻌﺮﻓﺔ اﻟﻄﺮﯾﻘﺔ اﻟﺘﻲ ﯾﺘﻢ ﺑﮭﺎ اﻟﺘﺰاوج ﺑﯿﻦ اﻟﺬﻛﻮر و اﻹﻧﺎث ﻹﻧﺘﺎج ﻛﻤﯿﺔ ﻣﻨﺎﺳﺒﺔ ﻣﻦ اﻟﺒﯿﺾ و رﻋﺎﯾﺔ ھﺬا اﻟﺒﯿﺾ ﻟﺤﯿﻦ ﻣﺮﺣﻠﺔ اﻟﻔﻘﺲ و ﻣﻦ ﺛﻢ رﻋﺎﯾﺔ اﻟﺼﻐﺎر . -2ﯾﻤﻜﻦ اﺳﺘﺨﺪام ﻣﺨﻠﻔﺎت اﻟﺨﻀﺮ واﻟﻔﺎﻛﮭﺔ واﻟﻤﺤﺎﺻﯿﻞ اﻟﻤﺨﺘﻠﻔﺔ ﻓﻲ ﺗﺼﻨﯿﻊ اﻟﻌﻼﺋﻖ اﻟﺘﻲ ﺗﺘﻐﺬي ﻋﻠﯿﮭﺎ اﻻﺳﺘﺎﻛﻮزا ﺣﯿﺚ أن ھﺬه اﻟﻤﺨﻠﻔﺎت ﺗﻤﺜﻞ ﻋﺒﺌﺎ ﻋﻠﻰ اﻟﺒﯿﺌﺔ وﺑﺬﻟﻚ ﺗﺘﺤﻮل إﻟﻰ ﻣﻮرد ﻃﺒﯿﻌﻲ . -3ﻣﻦ اﻟﻤﻤﻜﻦ اﺳﺘﺨﺪام ﻣﺎ ﯾﺘﺒﻘﻰ ﻣﻦ ﺟﺴﻢ اﻻﺳﺘﺎﻛﻮزا وھﻮ اﻟﺠﺰء اﻟﺬي ﻻ ﯾﺆﻛﻞ ﻓﻲ ﺻﻮرة ﻣﺴﺤﻮق ﯾﺪﺧﻞ ﻓﻲ ﻋﻼﺋﻖ ﻟﺘﻐﺬﯾﺔ دﺟﺎج اﻟﺘﺴﻤﯿﻦ و اﻟﺪﺟﺎج اﻟﺒﯿﺎض ﻋﻠﻰ اﻟﺴﻮاء و ذﻟﻚ ﻟﻠﺤﺼﻮل ﻋﻠﻰ ﻣﻨﺘﺞ ﻋﺎﻟﻲ اﻹﻧﺘﺎﺟﯿﺔ ﻣﻊ ﺟﻮدة اﻟﻠﺤﻢ ﻓﻲ ﺣﺎﻟﺔ دﺟﺎج اﻟﺘﺴﻤﯿﻦ وﻣﻦ اﻟﺒﯿﺾ ﻓﻲ ﺣﺎﻟﺔ اﻟﺪﺟﺎج اﻟﺒﯿﺎض . -4أوﺿﺤﺖ اﻟﺪراﺳﺔ اﻻﻗﺘﺼﺎدﯾﺔ أن اﺳﺘﺨﺪام ﻣﺨﻠﻔﺎت اﻟﺨﻀﺮ ﻓﻲ اﻟﻌﻼﺋﻖ اﻟﻤﻐﺬﯾﺔ ﻟﻸﺳﺘﺎﻛﻮزا ﺳﺘﻘﻠﻞ ﺳﻌﺮ اﻟﻄﻦ ﺑﻨﺴﺒﺔ . %80و ﯾﻨﺘﺞ ﻋﻦ ھﺬه اﻟﺘﻐﺬﯾﺔ ﺣﻮاﻟﻲ 60ﻛﺠﻢ ﻣﻦ اﻻﺳﺘﺎﻛﻮزا ﺑﮭﺎ ﺣﻮاﻟﻲ 5000ﻓﺮد ﺑﺎﻟﻎ ﺑﻤﺎ ﯾﺴﺎوي 900ﺟﻨﯿﮫ إذا ﻣﺎ ﺑﯿﻌﺖ ﻓﻲ اﻷﺳﻮاق اﻟﻤﺤﻠﯿﺔ ﻟﻼﺳﺘﮭﻼك اﻵدﻣﻲ .أﻣﺎ اﻟﺠﺰء اﻟﺬي ﻻ ﯾﺆﻛﻞ )اﻟﮭﯿﻜﻞ اﻟﺨﺎرﺟﻲ وﻛﺘﻠﺔ اﻷﺣﺸﺎء( ﻓﺘﺴﺘﺨﺪم ﺑﻤﺎ ﯾﻘﺎرب 711ﻛﺠﻢ ﻓﻲ إﻧﺘﺎج ﻋﻼﺋﻖ ﻟﻠﺪﺟﺎج واﻷﺳﻤﺎك وﺑﺬﻟﻚ ﺗﻮﻓﺮ ﺣﻮاﻟﻲ 300ﺟﻨﯿﮫ ﻟﻜﻞ ﻃﻦ ﻛﺎن ﻣﻦ اﻟﻤﻤﻜﻦ إﻧﻔﺎﻗﮭﺎ إذا ﻣﺎ اﺳﺘﺨﺪم ﻣﺴﺤﻮق اﻟﺴﻤﻚ .
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