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Exoskeleton&molting of insects
This document describes the structure and composition of an insect's exoskeleton. It is made of chitin microfibrils embedded in a protein matrix and arranged in multiple layers, with outer waxy layers that control water movement. The exoskeleton provides insects with protection and strength, with a tensile strength comparable to materials like Kevlar and bone. The document also outlines the 7 step molting process insects undergo to shed their exoskeleton and allow for growth, involving the formation of a new endocuticle underneath the old exoskeleton before it splits.
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Exoskeleton&molting of insects
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- 2. Insect Integument (Exoskeleton) Outerepicuticle Epicuticle Inner epicuticle Exocuticle Procuticle Endocuticle Schmidt’s layer Epidermis Basement membrane Pore canals
- 3. Insect Integument (Exoskeleton) Outerepicuticle Epicuticle Inner epicuticle cement wax oriented wax cuticulin Inner epicuticle Exocuticle (procuticle) pore canal
- 4. cement Insect Integument (Exoskeleton) wax orientedwax Wax Layers - Control of Water Movement WATER WATER WATER IS RETAINED
- 5. Insect Integument (Exoskeleton) N- acetylglucosamine polymer O = C - CH2 H NH CH2OH O OH H H H O H O H OH H H NH O CH2OH O = C - CH2 n
- 6. Insect Integument (Exoskeleton) O= C - CH2 NH H CH2OH O H OH H H H O OH H H H NH O CH2OH O = C - CH2 CO NH NH CO CO NH CO NH NH NH CO CO NH CO CO NH NH NH CO hydrogen bonds CO NH CO NH CO
- 7. Insect Integument (Exoskeleton) microfibril N- acetylglucosamine polymer sheets of microfibrils orientation of microfibrils changes
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- 9. Insect Integument (Exoskeleton) Crosslinking of protein matrix
- 10. Insect Integument (Exoskeleton) Crosslinking of protein matrix OH OH CH2 O OH O OH Protein CH2 N-acetyl dopamine C CH2 Protein OH CH2 CH2 OH Protein Protein CH2 CH2 N-acetyl dopamine quinone
- 11. Insect Integument (Exoskeleton) 100000 kg/mm2 10000 1000 100 10 1 Carbon nanotubes Graphitefibres Kevlar Steel Chitin Tensile strength of sclerotized chitin (sclerotin) Bone
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- 13. Molting • Arthropods periodicallyshed exoskeleton to allow for growth and/or metamorphosis • 7 steps during each molt cycle
- 14. 1. Apolysis • Retractionof epidermal cells from endocuticle • Formation of subcuticular space • Molting gel secreted • New cuticle laid down
- 15. 2. Epicuticle formation •Epicuticle laid down • It is extensively wrinkled
- 16. 3. Procuticle deposition •Formation of chitin microfibrils • Endocuticular layers of old cuticle digested • Enzymes in molting gel initially inactive
- 17. 4. Ecdysis • Old cuticlesplits along middorsal suture • Cast skin = epicuticle and exocuticle • Endocuticle recovered and recycled into new procuticle
- 18. 5. Expansion • Insectswallows air • Insect swells, removes wrinkles in epicuticle
- 19. 6. Hardening anddarkening • New procuticle stabilized • Exocuticle formed
- 20. 7. Endocuticle deposition •Depositing chitin and protein takes time • Some insects deposit one lamina of endocuticle every 24 hours Note: Ecdysis under hormonal control