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The Integument Week #2 External Morphology of Insects Consequences of having your skeleton on the outside 1. Muscles attach on the inside 2. The exoskeleton is also a suit of armor 3. Sensing the outside world is a challenge 4. Growth is impaired 5. There is a limit on insect size Parts of insects Integument (body wall) • – – – – Head • – – – – – • Thorax Skeleton Cuticle Formation Physical properties – – – – Segments Legs Wings Modifications • Abdomen Major functions Eyes Mouthparts: types and positions Antennae Modifications – Cerci – Ovipositor – Modifications The Integument Outer covering; includes cuticle and epidermis Cuticle The external skeletal structure, composed of chitin and protein Exoskeleton The external, hardened, cuticular skeleton to which muscles are attached internally 1 The Integument Consequences of having your skeleton on the outside 1. Muscles attach on the inside 2. The exoskeleton is also a suit of armor 3. Sensing the outside world is a challenge 4. Growth is impaired 5. There is a limit on insect size 2 The Integument Consequences of having your skeleton on the outside 1. Muscles attach on the inside 2. The exoskeleton is also a suit of armor 3. Sensing the outside world is a challenge 4. Growth is impaired 5. There is a limit on insect size The Integument Consequences of having your skeleton on the outside 1. Muscles attach on the inside 2. The exoskeleton is also a suit of armor 3. Sensing the outside world is a challenge 4. Growth is impaired 5. There is a limit on insect size Chitin, polysaccaride similar to cellulose; gives the cuticle its strength Chitin, a major cuticle component, is insoluble in water, alcohol, ether, dilute acids, and dilute or concentrate alkali. http://www.youtube.com/watch?v=IWRtJYW7GAs 3 Chitin is the main component of the cell walls of fungi, the exoskeletons of arthropods, including crustaceans, and the mouthparts of mollusks and cephalopods, including squid and octopuses. Fig 2.1 in textbook Epicuticle (0.1-3.0 μm) Structure: Inner epicuticle, outer epicuticle, superficial layer. Also, cement layer (shellac-like layer), wax layer, superficial layer (glycoprotein). Function: protection, water retention, serves as communication surface, sunblock. Cross‐section of the insect integument cement layer wax layer superficial layer outer epicuticle TEM of Larval Sclerite Epicuticle Wax filament inner epicuticle Exocuticle Endocuticle Pore canal exocuticle Epidermis 4 Procuticle (10-500 μm) Exocuticle: sclerotized endocuticle Endocuticle: lamellar sheets of chitin Procuticle (10-500 μm) Exocuticle: sclerotized endocuticle Endocuticle: lamellar sheets of chitin Chitin, polysaccaride similar to cellulose; gives the cuticle its strength Chitin, a major cuticle component, is insoluble in water, alcohol, ether, dilute acids, and dilute or concentrate alkali. 5 Epidermis- a major biosynthetic tissue, responsible for production of chitin fibrils, lipids, peptides and proteins found in cuticle (and hemolymph). Honey pot ant, Camponotus inflatus Basement membraneexocellular matrix that partitions insect tissues (connective tissue layer). Fig 2.1 in book Softer Side of the Exoskeleton Resilin: An elastic substance consisting of cross-linked protein chains, found in the cuticles of many insects ( intersegmental membranes, wing connective areas, leg joints (flea) Elastic cuticle regions contain high concentrations of resilin are not sclerotized. Cicada song: http://en.wikipedia.org/wiki/Cicada 6 Physical properties of cuticle: •COLOR •Permeability •Barrier to pathogens •External processes •Skeleton Physical properties of cuticle: COLOR 7 COLOR: Pigments…. From Insect Macroevolution Lecture Insects are arthropods phylum: Arthropoda They share many features with the annelids (phylum Annelida) and onychophorans (phylum Onychophora) Annelida Onychophora Onychophora Cuticle Color PIGMENTS Brown-black colordue to deposition of melanin Yellows to redscarotenoids, papiliochromes, flavonoids and pterines Red, blues, and greenstetrapyrroles 8 COLOR: Structural…. WIP diversity in small Hymenoptera. (A–C) Trichogrammatidae, three unidentified species (females, Costa Rica). Shevtsova E et al. PNAS 2011;108:668-673 ©2011 by National Academy of Sciences Physical properties of cuticle: Permeability 9 Physical properties of cuticle: block pathogens Thailand rainforest fungus with its carpenter ant victims •NW side of plant •25 cm up from surface •Ideal temp and humidity 10 Sandra B. Andersen, Sylvia Gerritsma, Kalsum M. Yusah, David Mayntz, Nigel L. Hywel Jones, Johan Billen, Jacobus J. Boomsma, and David P. Hughes, "The Life of a Dead Ant: The Expression of an Adaptive Extended Phenotype." The American Naturalist, Sept. 2009. Camponotus leonardi Physical properties of cuticle: External processes…. Mediterranean fruit fly (Ceratitis capitata) pulvillar pad with tenet setae. Pulvilli are the hairy adhesive organs at the end of fly legs. Tenet setae are the hairs (with adhesive ends) that make up the puvilli. The pulvilli allow the fly to attach to smooth surfaces. Sensillae or setae (hairs) © Dennis Kunkel. Spine Seta Acanthae Microtrichia 11 A hind leg of Leptoscelis tricolor (Hemiptera: Coreidae) Physical properties of cuticle: Skeleton Spines of beetles (Coleoptera) Insect parts: most information will be covered in lab and course notes Some highlights… 12 Thorax Myrmecomorphy – ant mimicking Family: Alydidae (Hemiptera) Antennae Mouthpart positions (head types) Contain complex of chemoreceptors, mechanoreceptors, thermoreceptors, and hygroreceptors used for : • Touch • Smell Humidity Hearing e.g. Many beetles Many insects Hypognathous projecting lower jaw Prognathous protrusive jaws Opisthognathous receding jaws e.g. Hemipterans (aphids, cicadas) Antennal Forms Opisthognathous A. setaceous (dragonfly) B. filiform (ground beetle) C. moniliform (bark beetle) D. clavate (darkling beetle) E. clavate (ladybird beetle) F. capitate (sap beetle) G. serrate (click beetle) H. pectinate (fire-colored beetle) I. plumose (mosquito) J. aristate (syrphid fly) K. stylate (snipe fly) L. flabellate (cedar beetle) M. lamellate (scarab beetle) N. geniculate (chalcid wasp) ar, arista; fl, flagellum; ped, pedicel; scp, scape; sty, style 13 Modifications of the thorax Entylia carinata (Hemiptera: Membracidae) (Orthoptera: Acrididae) Pronotum – design in shielding Ceresa basalis (Hemiptera: Membracidae) 14 Hemelytra membrane corium clavus Photo: Lyle Buss Heteropteran Hemiptera Types of Insect Legs Cursorial (to run) Elytra Natatorial (Swimming) Raptorial (to prey) Saltatorial (leap) Fossorial (to dig) Prehensile Membranous Wings Tergum Sternum 15 Examples of Ovipositors Modifications in the abdomen Formosan Termite Queen Isoptera (now Blattaria) Examples of Cerci 16