Parts of Insects the Integument Cuticle Exoskeleton

The Integument

Week #2 Consequences of having your skeleton on the outside External Morphology 1. Muscles attach on the inside of Insects 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) • Thorax – Skeleton – Segments – Cuticle – Legs – Formation – Wings – Physical properties – Modifications • Head • Abdomen – Major functions – Cerci – Eyes – Ovipositor – Mouthparts: types and – Modifications positions – Antennae – 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

The Integument

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) Cross‐section Structure: of the insect Inner epicuticle, outer epicuticle, superficial layer. integument Also, cement layer (shellac-like layer), wax layer, superficial layer (glycoprotein). Function: protection, water retention, serves as communication surface, sunblock.

cement layer wax layer TEM of Larval Sclerite superficial layer outer epicuticle Epicuticle

Wax filament inner epicuticle Exocuticle

Endocuticle Pore canal exocuticle

Epidermis

4 Procuticle (10-500 μm) Procuticle (10-500 μm) Exocuticle: sclerotized Exocuticle: sclerotized endocuticle endocuticle Endocuticle: lamellar sheets Endocuticle: lamellar sheets of chitin 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 Honey pot ant, biosynthetic tissue, Camponotus responsible for production of inflatus chitin fibrils, lipids, peptides and proteins found in cuticle (and hemolymph).

Basement membrane- exocellular 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 color- due to deposition of melanin

Yellows to reds- carotenoids, papiliochromes, flavonoids and pterines

Red, blues, and greens- tetrapyrroles

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

Physical properties of cuticle: Permeability

9 Physical properties of Thailand rainforest cuticle: block pathogens 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 Humidity • Smell Hearing

Many insects e.g. Many beetles Hypognathous Prognathous protrusive jaws projecting lower jaw

Opisthognathous receding jaws e.g. Hemipterans (aphids, cicadas)

Antennal Forms A. setaceous (dragonfly) Opisthognathous 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

Raptorial Cursorial (to prey) Elytra (to run) Saltatorial (leap)

Prehensile Natatorial Fossorial (Swimming) (to dig)

Membranous Wings

Tergum

Sternum

15 Modifications in the abdomen Examples of Ovipositors

Formosan Termite Queen Isoptera (now Blattaria)

Examples of Cerci