The cuticular structure

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Ashley Robbins
6 years ago
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The Exoskeleton = key contributor to insect success External : exoskeleton,

fore and hindgut Ranges from rigid/armor like (beetles) to flexible and pliable

wax layer (prevents dehydration) and inner epicuticle (cuticulin layer =

(sclerotization), thick endocuticle, sclerotization = tanning = cross-linkages with

1 The Exoskeleton = key contributor to insect success External : exoskeleton, apodemes, wings => barrier to outside environment Internal: tracheal tubes, glands, fore and hindgut Ranges from rigid/armor like (beetles) to flexible and pliable (larvae) The cuticular structure Epicuticle - cement layer (protects from abrasion, wax layer (prevents dehydration) and inner epicuticle (cuticulin layer = lipoproteins/fatty acids) Procuticle chitin complexed with protein, thin exocuticle (sclerotization), thick endocuticle, sclerotization = tanning = cross-linkages with quinone Epidermis - single celled live layer Basement membrane mucopolysaccharides/collagen fibers 1

formation Dermal glands - composed of 3 cells (1 producing, 2 canals), products formed

2 Basement membrane - continuous with sarcolemma Epidermis - single cell layer, dermal glands, desmosomes, secretes cuticle = living integument Schmidt layer - zone of formation Dermal glands - composed of 3 cells (1 producing, 2 canals), products formed in vacuoles = cement Oenocyte large fatty acids, water proofing of cuticle, pheromonal communication 2

colorless rubber-like protein found in elastic cuticle hinges ligaments, between tergum/pleurum amino acids linked to proteins amino acid sequence prevents other cross-linkages Resilin Cuticular

3 colorless rubber-like protein found in elastic cuticle hinges ligaments, between tergum/pleurum amino acids linked to proteins amino acid sequence prevents other cross-linkages Resilin Cuticular Modifications Acanthae Microtrichia Multicellular Spine Setae or sensillum Multicellular spine = undifferentiated epithelial cells, robust Setae = also called hairs, sensory Acanthae = unicellular, small protrusions Microtrichia = subcellular, multiple extensions per cell When mobile referred to as spurs 3

$Physical coloration = light scattering, interference and diffraction 2.$ Pigment colors: Melanin - brown and black (cuticle), same pigment as in human skin, some darkening results from

Pigment colors: Melanin - brown and black (cuticle), same pigment as in human skin, some darkening results from

β-carotene, xanthophyll) Pterines - nitrogen containing compounds, synthesized from purines, leucopterin (white),

Odonata, also provide eye color Tetrapyrroles - porphyrin with iron, only present in few insects living in anoxic

4 Colors in Insect Integuments production by interaction of light with underlying cells 1. Physical coloration = light scattering, interference and diffraction 2. Pigment colors: Melanin - brown and black (cuticle), same pigment as in human skin, some darkening results from tanning, granular melanin typical Carotenoids of plant origin, not insect synthesized, yellow, orange, red (α & β-carotene, xanthophyll) Pterines - nitrogen containing compounds, synthesized from purines, leucopterin (white), xanthoptrin (yellow), Erythropterin (red), important in Lepidopterans Ommochromes - tryptophan derived, reds, browns in Odonata, also provide eye color Tetrapyrroles - porphyrin with iron, only present in few insects living in anoxic conditions Quinone pigments - anthraquinones (3 benzene rings, carminic acid, in eggs) and aphin (purple or black of aphids) Flavones - plant pigment in some true bugs and Lepidopterans, i.e. color of marbled white butterfly 4

5 Insect Tagmosis three familiar tagmata: head (6 segments), thorax (3 segments), abdomen (11 segments) 20 original segments in larvae various degrees of fusion (head/abdomen) dorsum, tergite pleurum (x2), pleurite venter, sternite 5

6 Primary segmentation superficial Secondary segmentation conjunctival or intersegmental membrane (abdominal), muscles attached to solid cuticle The Head antennal preantennal labral labial mandibular maxillary Cranial capsule with 2 openings = occipital foramen, mouthparts 6

(paired, sensory palps) Labium (lower lip, labial palps) Hypopharynx

7 Mouthparts Labrum Maxilla Cutting Molar Teeth Mandible palp Labrum (upper lip, generally flap-like) Mandibles (lower jaws, often toothed, paired) Maxillae (paired, sensory palps) Labium (lower lip, labial palps) Hypopharynx (tongue-like structure) Palps Gula Hypopharynx Labium Hypognathous Prognathous Opisthognathous 7

Coleoptera, typical arrangement Antennal

8 Sucking = Lepidoptera, Mouthpart Adaptations proboscis, modified maxillae Piercing = mosquito, labial sheath, tubular labrum, stylet =maxillae/ mandibles Sponging = Diptera, articulated sponge-like labellum, mandibles/ maxillae reduced, nonfunctional Chewing = Odonata, Coleoptera, typical arrangement Antennal Structure Pedicel => stem Flagellum => generally annulated, multiple portions annulated versus segmented antennae = musculature annular # increases during post-embrionic life 8

9 Antennal Function olfactory sensation, proprioceptors, thermohygroceptors Variation in Form = sexual dimorphism Filiform Moniliform Clavate Serrate Pectinate Flabellate Geniculate Typical Pterygote Plumose Aristate Diptera 9

Integument: Structure & Function. 1 February 2010

Integument: Structure & Function 1 February 2010 Terrestriality Insects are one of the few lineages to have successfully colonized terrestrial environments. What are some of the other major lineages? Terrestriality