International Journal of Marine Science 2015, Vol.5, No.3, 1-7 http://ijms.biopublisher.ca
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First report on mass reproductive swarming of a polychaete worm, Dendronereis aestuarina (Annelida, Nereididae) Southern 1921, from a freshwater environment in the south west coast of India P.R. Jayachandran, M.P. Prabhakaran, C.V. Asha, Akhilesh Vijay, S. Bijoy Nandan Department of Marine Biology, Microbiology & Biochemistry, School of Marine Sciences, Cochin University of Science & Technology, Cochin-16, India Corresponding author email:
[email protected] International Journal of Marine Science, 2015, Vol.5, No.3 doi: 10.5376/ijms.2015.05.0003 Received: 25 Oct., 2014 Accepted: 23 Nov., 2014 Published: 05 Jan., 2015 Copyright © 2015 Jayachandran et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Jayachandran et al., 2015, First report on mass reproductive swarming of a polychaete worm, Dendronereis aestuarina (Annelida, Nereididae) Southern 1921, from a freshwater environment in the south west coast of India, International Journal of Marine Science, Vol.5, No.3 1-7 (doi: 10.5376/ijms.2015.05.0003)
Abstract In the present study we report the occurrence of red coloured mass reproductive swarms of Dendronereis aestuarina from Periyar River of the south west coast of India. It was observed in the freshwater zone of the river during the evening hours of August 31st, 2010. Reproductive swarming behaviour of D. aestuarina has been first reported by Southern, 1921 from brackishwater environment in the Gangetic delta, however present study reports first time from absolutely freshwater environment. The density of swarmed polychaete was ~14800 indls. m-2 with the average length of 86 ±16 mm. Male worms were dominated in the 60 specimens analyzed and the sex ratio was 3:1 (M/F). The average diameter of eggs collected from polychaete body was 0.33 ± 0.08 mm. Swarming was extended for two days; after successful mating and spawning they were died. Keywords Dendronereis aestuarina; Reproductive swarming; Periyar River; Cochin estuary; Kodungallure - Azhikode estuary
Introduction
aquatic environment and energy flow through different food chains (Nair et al. 1984). The breeding and spawning of polychaetes are induced by various biotic and abiotic factors such as temperature, endogenous and lunar timing, while swarming is controlled by daytime, tide, environmental and endocrine factors like pheromones (Gaston and Hall 2000, Andries 2001). Temperature is assumed to be one of the most important external factors synchronizing maturation and spawning in marine invertebrates (Tsuji and Hill 1983, Hardege et al. 1990, Fong and Pearse 1992, Ajmal Khan 2006, Lawrence and Soame 2009).
The polychaetes worms are generally found living in all marine environments, some floating freely near the surface or the bottom (pelagic fauna), some others, as part of the benthic fauna, burrowing in the mud, sand and rocks of seashores down to abyssal depths and they can even colonize non marine habitats, such as freshwater and others aquatic systems (Southern 1921, Fauvel 1953, Nyman et al. 1995, Hutchings 1998, Bakken and Wilson 2005). Over 10,000 species have been described to date, belonging to 83 recognized families, and various estimates have been made to the total polychaete fauna ranging from 25,000 to 30,000 (Snelgrove 1997, Rouse and Pleijel 2001). They exhibit considerable variations in recruitment both in time and space, which is then often reflected in adult distribution. The families and genera of polychaetes have wide distributions while, normally, species have discrete distributions (Hutchings 1998, Ajmal Khan and Murugesan 2005). A quantitatively enhanced population indicates that input of organic matter stimulates benthic productivity (Ansari et al. 1986). They are involved in demineralization and recycling processing of organic and inorganic matters in the
The Nereididae (Blainville, 1818) is among the most diverse of polychaete families, comprising over 540 species and 43 genera (Beesley et al. 2000). They are most common in shallow marine habitats, but the Nereididae are the ones that have been more commonly found in freshwater environments compared to other polychaete families (Bakken and Wilson 2005). The variety of Nereididae species being commercially harvested for fish bait and used as test organisms in research related to physiology, endocrinology and the environment (Nithart 2000, 1
International Journal of Marine Science 2015, Vol.5, No.3, 1-7 http://ijms.biopublisher.ca Bakken and Wilson 2005). These organisms are important in the form of diet for many fishes and invertebrates (Gottfried Pillai 1965, Chan 2009, Bijoy Nandan et al. 2012, Jayachandran et al. 2013). Some species commonly live in large numbers in the intertidal zone of estuarine and brackish waters, normally in sediments of medium to high organic content (Bent 1967).
of the south west coast of India (Ramachandra et al. 1984, Sarala Devi et al. 1991a, Prabhu et al. 1993, Sheeba 2000, Feebarani 2009). Among the 34 estuaries of the south west coast of India, the largest number of polychaetes species (19) were recorded in the Cochin estuary (Ajmal Khan and Murugesan 2005). However, there were no previous reports on reproductive swarming of Dendronereis aestuarina Southern, 1921 in the estuarine and riverine conditions of the south west coast of India. The present study is the first report on mass reproductive swarming of D. aestuarina on purely freshwater environment and second report on mass reproductive swarming.
Nereididae species exhibit a wide range of reproductive modes, including external brooding, viviparity and hermaphroditism (Dorresteijn and Westheide 1999). Most species undergo morphological and physiological modifications when they become sexually mature, suiting many of them for a brief pelagic existence and improving the chances that sexual partners will find each other (Chatelain et al. 2008). All Nereididae polychaetes have a semelparous life cycle; they reproduce once in a lifetime and die soon after spawning (Dorresteijn and Westheide 1999). The reproductive swarming of the Nereididae to the surface waters of marine and estuarine environments is a well-known phenomenon (Tampi 1958, Read 1974). A conspicuous breeding behaviour, swarming (mass aggregation of sexually matured adults for spawning in the surface water), with or without typical metamorphosis to the pelagic epitokal (heteronereis) form, is known in many Nereididae species (Hanafiah et al. 2006). Metamorphosis of the immature worm into a special reproductive form is known as epitoky (Chatelain et al. 2008). This is the formation of pelagic, reproductive individuals, known as epitokes, from benthic non-reproductive individuals, or atokes. The production of epitokes usually occurs synchronously in an entire population, correlated with lunar and tidal cycles (Rouse and Pleijel 2001) . Swarming epitokes can be very conspicuous due to the sheer numbers of worms, especially if they are bioluminescent (Schulze and Timm 2012). These types of reproductive strategies enabled them to build up large populations over very short time periods (Hutchings 1998).
1 Materials and Methods The swarming of Dendronereis aestuarina occurred in the riverbank (Aluva Manapuram) (Figure 1) of Periyar River (10°6'N, 76°21'E), south west coast of India. At this point, the river bifurcates into the Marthandavarma and the Mangalapuzha branches. The Mangalapuzha branch joins Chalakkudy river and empties into the Lakshadweep sea at Munambam, and the Marthandavarma branch flows southwards, through the Udhyogamandal area and joins the Cochin backwater system at Varapuzha (Government of Kerala 2009). The tidal cycle in these estuaries was semidiurnal with microtidal range (0-2m); tidal influence extended to approximately 25km landward. The study area is located ~33 km landward from mouth of Cochin estuary; not under tidal influence. The average rainfall in the study area was 310 cm/year and characterized by a totally freshwater environment during the monsoon, post monsoon and summer season
Polychaetes are commonly found in Indian estuaries, among 152 species recorded, 119 species from east coast, 10 species from west coast and 23 species were recorded from both east and west coasts. Many investigations were carried out on the abundance and distribution of polychaetes in the estuarine environments
Figure 1 Location (O) of Dendronereis aestuarina swarming observed in the Periyar River (Aluva Manapuram) 2
International Journal of Marine Science 2015, Vol.5, No.3, 1-7 http://ijms.biopublisher.ca (Revichandran and Abraham 1998, Government of Kerala 2009, Jayachandran and Bijoy Nandan 2012, Jayachandran et al. 2012b). The present swarming occurred in the first quarter of the moon; however, the study area is not under tidal influence.
[NTU- Nephelometric Turbidity Units]). However, dissolved oxygen content in the water column was quite low (2.9 ml L-1) and pH slightly acidic in nature (6.5).
The swarms occurred in the first quarter moon (7 days after full moon). The swarmed individuals were observed in the submerged concrete blocks (
