Cuticles And Moulting Flashcards
(11 cards)
What are the functions of cuticles?
Barrier Apodemes Forms wings and legs Forms sense organs Colouring and pattern Lining of tracheal tubes, gland ducts and fore- and hind guts Can greatly reduce water loss Can protect the animal mechanically
What is the function of cuticles?
Protection from dessication
Describe the general structure of the cuticle
Thin and complex, secreted by basal epidermal cells Made up of three layers- Epiculticle (cement, wax, superficial) Exocuticle Endocuticle Epidermal layer
Describe the three types of epidermal layers
1) pheromone production: no duct, secretion travels to cuticle via pore canals
2) no duct or path to cuticle
3) a duct connects the gland to the cuticle. Gland cell has a specialised folded cavity to house the secretions before they are transported via the duct cell to there epicutcile.
Function of epidermal layer
Hydrophobic secretion in aquatic insects
Keeps water away from spiracles
Pheromone secretion
Produce cement layer of epicuticle
What is a lamellate cuticle?
Microfibrils embedded in parallel lines in sheets of rewrote in matrix with each sheet rotated slightly clockwise
Why is moulting necessary
Hardened cuticle cannot stretch
Describe the stage of apolysis
Separation of old cuticle from epidermis.
Old cuticle separates from the epidermis caused by plasma membrane of the epidermal cells forming vesicles whic break, releasing a foam into the growing exuvial space. This space then fills with moulting fluid and a new cuticle is formed on top of the epidermis
Describe the process of moulting
Apolysis.
Formation of the new cuticle: forms at the tips of The microvilli of epidermal cells.
Digestion of old endocuticle: epidermal cells release chitinase and proteases (moulting fluid) which is only activated after the formation of the new epicuticle and is associated with the flow of H2O and potassium into exuvial space. Most of the old endocuticle is fdigested. The old cuticle is very thing ow, especially along ecdysial lines.
Ecdysis: the old cuticle separates from the new one and splits along ecdysial lines. Air swallowed puts pressure on haemolymph in thorax. New cuticle is soft and unexpanded.
Describe the three types of cuticles
Soft cuticle: more aspartic acid, glutamic acid and amino acids
Hard cuticle: hardening (sclerotisation) occurs via cross linking these proteins, produced a tanned cuticle
Elastic: colourless and contains resilin. When this stretches, it stores energy and on the release, it snaps back to its original length
How is the new cuticle expanded.
Air or water is swallowed using pharyngeal muscles which results in increase in blood pressure. Actual expansion results from opening of the folds in cuticle.
