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