Exoskeleton vs. Endoskeleton: biomechanical trade-offs Other advantages of the exoskeleton.. The necessity of molting allows Complete Metamorphosis Hercules beetle (Dynastes hercules) strength of skeleton exoskeleton endoskeleton Shrew (Sorex sp.) The cuticle includes a Lipid Monolayer size of organism What about six legs?? may not be monophyletic Entognathous hexapods:,, (springtails): : oral cone (collophore) 12 : : (springtails, snow fleas) 6000 species 12-20 families 4 subclasses (Lower Devonian) : ( proturans ) 500 species 3-8 families 2 subclasses (Devonian) 1
: ( diplurans ) 800 species 5-9 families 2 subclasses (Carboniferous) The three major evolutionary innovations of the : flight, wing-folding, & 1. 2. 3. (= Microcoryphia, Machiloidea) Apterygota: (bristletails) 450 species, 2 families (Thysanura) mandibles (mono- vs dicondylic) Monura? maxillary & labial palps 5 mm Permian Dasyleptidae (Elmo fauna) median caudal filament APTERYGOTA Apterygota: (silverfish & firebrats) 370 species, 3-4 families 2 condyles Apterygota are paraphyletic: (Bitsch & Nel 1999, von Lieven 2000) Outgroup (monocondylic) dicondylic mandible? Monura (extinct) (=Microcoryphia) (=Thysanura) (other insects) Apterygota are monophyletic: Thysanura s. lat. (Koch 2001 [morphology], Regier 2004 [molecules]) Lepisma sp. Thermobia sp. 2
The Origin of Wings:, : (mayflies) 2500 species, 6 superfamilies, 21-23 families adult naiad (nymph) Mayflies, : (dragonflies & damselflies) 6500 species, 2 suborders, 27 families s.o. Anisoptera (dragonflies) s.o. Zygoptera (damselflies) s.o. Anisoptera (dragonflies) Thoracic tilt s.o. Zygoptera (damselflies) Tracheal gills Anisoptera naiad (rectal gills) Zygoptera (caudal gills) 3
Damselflies Dragonflies Meganeura (Protodonata) (Carboniferous, approx 320 mya) 28 inches (70 cm) (from Jeannel 1960) Phylogenetic hypotheses for I. are monophyletic (Hennig) Outgroup II. are paraphyletic (Kristensen) (Boudreaux) Outgroup Outgroup (all other insects) (all others) The morphological basis of wing-folding (neoptery) The Origin of Wing-Folding: 4
adult: Plecoptera (stoneflies) 2000 species, 2 suborders, 16 families Grylloblattodea (ice or rock crawlers) 24 species, 1 family (Grylloblattidae) naiad: (nymph) Dictyoptera, s.o. Blattodea (cockroaches) 3500 species, 6 families Cockroaches, past & present: Periplaneta americana 300 my-old fossil, 4 long Blattella germanica Dictyoptera, s.o. Mantodea (mantises) 2300 species, 8 families Dictyoptera, s.o. Isoptera (termites) 2600 species, 7 families oetheca 5
Phasmatodea (stick & leaf insects) 3000 species, 3 suborders, several (?) families Dermaptera (earwigs) 1800 species, 3 suborders, 10 families s.o. Arixenina s.o. Forficulina suborder Caelifera (11,000 spp): Acrididae (short-horned grasshopper) Orthoptera (grasshoppers, crickets, katydids) suborder Ensifera (11,000 spp): crickets, katydids, long-horned grasshoppers Embiidina (webspinners) 300 species, 2 suborders, 8 families s.o. Hemimerina ear Timema sp. ear Mantophasmatodea (gladiators, heelwalkers) 16 species, 3 families Specialized without : the Paraneoptera,,, Paraneoptera: smaller hemipteroid orders Zoraptera Thysanoptera: thrips (28 spp) (4700 spp) Psocoptera: book lice (2500 spp),,, Paraneoptera: Hemiptera s.o. Auchenorrhyncha (25,000 spp): cicadas and hoppers Phthiraptera: Membracidae Cicadellidae Cicadidae s.o. Mallophaga, s.o. Anoplura, biting lice (5000 spp) sucking lice (500 spp) s.o. Sternorrhyncha (25,000 spp): aphids, scales, whitefies, other plant lice Fulgoroidea: plant hoppers 6
,,, Paraneoptera: Hemiptera s.o. Heteroptera the true bugs (30,000 species) Lygaeidae (seed bugs) Coreidae (squash bugs) Pentatomidae (stink bugs) Miridae (plant bugs) Nepidae (water bugs) 7