I. Integument as exoskeleton. II. Structure. A. Major Components. B. Composition.
III. Insect body plan. IV. Introduction to Insect. Orders ...
I.
Integument as exoskeleton
II. Structure A. Major Components B. Composition III. Insect body plan IV. Introduction to Insect Orders
Integument as exoskeleton – Complex structure of diverse function •
Nearly unlimited area for muscle attachment (and organ attachment)
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Protective – physical protective surface
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Protective – Biological (pathogens, virus, fungus etc)
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Water Retention
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Interface b/t insect sensory & exocrine structures and environment.
Integument as exoskeleton – Other functions •
Feeding – mouthparts, variations and strength
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Locomotion – wings, legs and prolegs
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Reproduction – external genitalia are exo modifications
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Many internal parts are also lined integument – tracheal system, fore & hind gut and must be shed when molting
Epidermis - composed of 3 layers – From the inside out: •
Basement Membrane – Noncellular layer – 0.05 µm – micrometer (1/1000)
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Epidermis – Cellular layer ‘alive’
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Cuticle – Noncellular layer – can be up to ½ dry weight (but varies)
Basement Membrane – Basal Lamina: • •
Noncellular layer – 0.05 µm thick Composed of “amorphous granular material” most likely Mucupolysaccharide
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Provides support for epidermal cells
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(-) charged and physical properties = effective sieve
Epidermis – cellular and biologically active part of integument • • • •
Cellular layer responsible for secreting both basal lamina & cuticle Typically only one cell layer thick Most important tissue b/c it regulates molting, type of cuticle to lay down, placement of specialized cells (sensory, scales etc) Interspersed w/in epidermis are dermal glands (associated w/ cuticle production) with pore canals leading into cuticle
Cuticle – noncellular layer, complex • •
Properties vary spatially, temporally contingent upon demands of function and growth Chemical and physical properties of regions reflect locally specific genetic expression of epidermis
Cuticle – can be divided into 4 basic regions (from inside out) • • • •
Endocuticle – composed of growth layers (light and dark layers corresponding to daily cycles Mesocuticle – only know it b/c it stains, function unknown Exocuticle – Highly stable, resistant to molting fluid – exuvia Epicuticle – very thin yet very complex
Cuticle – Epicuticle 0.03 um – 4 um thick, procuticle up to 200 um • • •
Endocuticle and Exocuticle together comprise the Procuticle Compared to hard areas of cuticle, softer regions typically comprised of only endo- & epicuticle – referred to as arthrodial membrane Laid down lamellate at right angles (dark layers = day, light layers = night)
Epicuticle – Cement layer Superficial layer Outer epicuticle Inner epicuticle
Cement Layer • • • •
Not present in all spp Produced by dermal glands Provides protection for layers below Similar to shellac
Superficial Layer •
• •
Composed of two parts: oriented and randomly oriented wax molecules (monolayer) Critical for conserving water Lipids and hydrocarbons (recognition, sex attractants, mounting stimulants etc) H2O loss
Temp
+ Heat =
Outer Epicuticle • •
1st layer to be secreted for new cuticle Covers all integument surface including gut and tracheae
Inner Epicuticle •
Thought to be responsible for limiting cuticle expansion b/t molts
Chemical composition of Cuticle • •
Chitin – 25 – 50% dry weight – polysaccharide mostly N-acetylglucosamine Proteins – Major constituent several kinds: A – Sclerotins – involved w/ xlinking protein molecules and hardening B – Arthropodins – soluble proteins C – Resilin – stretchy, rubbery protein, stores energy, common around wing hinges etc.
GENERAL INSECT BODY PLAN
GENERAL INSECT BODY PLAN Tagma Head = 3 segs pregnathal & 3 gnathal segs (mandibles, maxillae, labium) Thorax = 3 segments each w/ 1pr of legs; each true leg has 6 segments (extant, 11 ancestral)
Head
Thorax
Thorax
Abdomen
Epiclass: Hexapoda United by: •Fusion of 2nd maxillae into labium •Fixed # ab segs @ 11 – Ancestrally •Tagmosis – head, thorax, ab (body segs unite to form tagma)
What makes things baffling is their degree of complexity, not their sheer size; a star is simpler than an insect - Martin Rees, 1999 (The Scientific American)
Entognatha Primary Characters uniting this group: •Mouthpart appendage recessed into gnathal pouch – this is a derived condition (apomorphy) ancestrally arthropods are ectognathus. •Mandibles monocondylic (articulated singly) – also only this group of hexapods that have protrusible and retractable mandibles (Insects – only maxillae do that) •External fertilization – possess gonopores for depositing and receiving spermatophore • Molting occurs after adult stage is reached
Order: Protura - “first – tail” Characters: •Minute (~ 0.5 – 1.6mm) •Head conical, scraping mouthparts •No eyes or antennae •1st pair of legs – sensory •12 abdominal segments (in adult) •1 ab. seg. added each molt (9-11) (anamorphic) •Gonopore on Ab 11 •Rudimentary appendages On 1st 3 Ab segs
Order: Protura Biology • ~ 500 species world wide •Moss, rotting wood, soil, leaf litter etc. •Thought to feed on mycorhizal fungus •Biology poorly known •Functionally “tetrapods” •Virtually no fossils
Order: Collembola “glue-wedge” Characters: • Reduction of ab segs to 6 (appears fewer) • Abdomen w/ sucker-like ventral tube – collophore (1) retaining hook (3) and furcula (4), gonopore (5), anus (6) • larval development epimorphic (no segs added)
Order: Collembola Biology: •9000 sp WW •Most common ‘entognath’ • 3 – 6 mm • Feed on decaying matter, fungus, bacteria, pollen, feces, etc • Very numerous – up to 100k per m3
Order: Diplura “two-tail” Characters: • Two caudal filiments • eyes, ocelli absent • antaenna long • Styli present on ab segs (1/2 – 7)
Order: Diplura Biology: • 1000 sp WW •< 7mm usually • Dwell in soil • Biology poorly known • No fossils
Class: Insecta United by: • Typically ocelli/compound eyes • Ectognathous w/ mouthparts well developed • Thoracic legs w/ > 5 segs • Ab ancestrally 11 segs w/ gonopore female (8), male (9) • Cerci present basally • Gas exchange via trachea – many mods
Mandibles monocondylic (articulated singly)
A - Insects
The Apterygote Insects Order: Microcoryphia “small-head” – Jumping bristletails Characters: • Cylindrical body • Compound eyes large and contiguous, ocelli always present • 3 caudal filaments
Order: Microcoryphia Biology: • ~ 500 sp WW •Many ecosystems • Most nocturnal • Active – can leap 25 cm!
Order: Thysanura “fringe-tail” Characters: • Compound eyes widely seperated • ~ 500 sp WW Habitat: feed on starchy products • Can be a problem for books, bindings with glue, •Look in the bathroom
Infraclass – Pterygota Paleoptera (informal grouping) • Lack wing flexion mech to fold wing over ab • Only extant orders of once diverse lineage
Order: Ephemeroptera “Short-lived” Characters: • 3100 sp WW •Most basal extant lineage of winged insects. • Mouthparts vestigial as adults and that phase lasts 1 day • Aquatic larvae (not an ancestral condition) • Feed chiefly on algae and detritus
Order: Odonata “tooth” Characters: • 5500 sp WW •All nymphs are aquatic and predaceous • Highly active flying hunters • Many aquatic environments
Neoptera – new winged insects Able to fold wings over ab
Order: Plecoptera “folded/plaited-wings” Characters: • 2000 sp WW •Nymphs are aquatic • Both adults and larvae feed on algae
Order: Blattodea and the subsuming of Isoptera?
Super Order: Dictyoptera Orders: Mantodea, Blattaria, Isoptera (1800, 4000, 2900 sp WW) Closely related but now it seems that Isoptera is a highly derived family of Blattaria.
Order: Gryllobattodea • 41 sp WW •Discovered in 1914 • 15-30 mm • 25 sp WW • Live in extreme environments
Order: Mantophasmatodea • 1st described in 2001 from 30 my amber • 20 - 30mm • One family and 3 genera • Predaceous • S. Africa, now known for its endemism (~41 sp)
Order: Phasmatodea • 3000 sp WW •Slow moving herbivorous • 2000 species WW • Widely dist, but richest in the tropics
Order: Embiidina “lively” • 500 sp WW •Superficially resemble Plecoptera •Produce silk from cellular glands on anterior basal tarsus • Spend life in spun silken galleries in litter, soil, rocks, etc • One introduced sp in NA is Parthenogenic • Adult males do not eat
Order: Orthoptera “straight -wings” • ~ 20,000 species • Known for their enlarged hind legs – jumping • Many produce sound via stridulation • Early branch in polyneoptera • Herbivore – Omn – Predatory
Order: Dermaptera “skin – wing” • ~ 2,000 WW • modified forewings, under which the hind wings fold • largely nocturnal, feed on detritus but can be a pest
Order: Zoraptera “pure-wingless” • 32 sp WW • < 3mm • principal food is fungal spores – we think • Can be found in ‘colonies’ under bark
Sub Division Paraneoptera – Hemipteroid assemblage
Order: Psocoptera “rub small” • 4400 sp WW • < 6mm • Feed on spores, algae, molds, cereals • Either gregarious or not • Certain sp can vector fringed tapeworm of sheep
Order: Phthiraptera “lice – w/o wings” • 4900 sp WW • Small wingless ectoparasites on birds and mammals • Both chewing and sucking types, which are distinct
Order: Hemiptera • 90,000 sp WW • All life histories practiced • Most diverse Hemimetabolous insects • Sucking mouthparts • Lumpers/splitters
Order: Thysanoptera “fringe” • 5000 sp WW • 0.5 – 5mm • Many feed on living plant material, some predators • Metamorphosis is somewhat intermediate b/t Hemi and Holo – metabolous insect – 1st 2 instars – no visible wing pads and other features • Very Numerous
Sub Division Endopterygota – Holometabolous insects
Order: Neuroptera “nerve - wings” • 6500 sp WW • Most larvae predaceous, many are aquatic (not lacewings) • Adults weak flyers • Some (Rhaphidioptera) are parasitic in spider egg sacks
Order: Coleoptera “sheath - wings” • 350,000 sp WW • ALL habitats exploited
Order: Strepsiptera “twisted - wings” • 550 sp WW • Parasitic on other insects • Males winged, Females highly modified • The Enigmatic Order • Life cycles very complex
Order: Diptera “two - wings” • 120,000 sp WW • Pervasive • Most agile flyers • Hind wings reduced to halteres (gyroscopes) • Exploit any and all niches
Order: Mecoptera “long - wings” • 600 sp WW • 9 – 25 mm • Pronounced ‘beak’ • Most generalized Holometabolous insect • Complex mating rituals involving nuptial gifts
Order: Siphonoptera “tube - wingless” • 2500 sp WW • Small • Compressed laterally •Highly modified ectoparasites • Adults depend on blood of warm blooded verts (w/ rare exception) • Larval are free living feeding on organic matter • Covered in stiff backward facing setae and spines
Order: Trichoptera “hair – wings” • 11,000 sp WW • Aquatic larvae live in various freshwater conditions • Larvae construct cases out of material that is species specific
Order: Lepidoptera “scale - wingless” • 150,000 sp WW • Most recognizable and liked insect (at least butterflies) • Larvae have large impacts on ecosystems (herbivory)
Order: Hymenoptera “god of marriage” • 125,000 sp WW • Ants, Bees, Wasps • Also have large impacts of ecosystems. Hmmm….. Let me count the ways
