Lecture 7: Cuticle Flashcards
Structure of the cuticle:
- Epidermis Basal lamina
- Procuticle; Endocuticle and exocuticle
- epicuticle
are the endo and exo cuticle always the same ratios?
NO
-endo usually bigger but not necessarily
the epistle structure ____ in insects
varies
Epicuticle structure:
OUTSIDE
- cement layer
- superficial layer
- lipid monolayer
- -(wax canal starts continues through exocuticle where becomes pore canal)
- outer epicuticle
- inner epicuticle
2 most important layers of epicuticle:
- cement layer
- lipid monolayer
cement layer:
- shellac like proteins
- maintains integrity
lipid monolayer:
- protects against water loss
Procuticle: Exocuticle
- Thicnkness varies - thick in stiff cuticle, non-existent in pleural membranes
- hard and dark - melanised + sclerotised
- proteins are cross-linked by “Tanning” - makes one of the strongest biopolymers known
- by incorporating micro-fibres of chitin in parallel arrangements in off-set sheets: makes cuticle VERY strong
Procuticle: Endocuticle:
- thickness varies - thin in stiff cuticle, makes up pleural membrane
- flexible and often transparent - no melanisation or sclerotisation
- contains novel insect protein called “RESILIN” - v rubbery
- endocuticle is important in many cuticular hines and springs
- because it is not cross linked like exocuticle it can be recycled during moults
Moulting steps:
1) nuclei & cells of basal lamina get larger + space between old cuticle and epidermis forms –> EXUVIAL SPACE
2) exuvial space filled with moulting fluid (INACTIVE) and new epicuticle begins to form
3) another membrane (ECDYSIAL membrane) separate active and inactive mf. Active MF digests & recycles old endocuticle
4) new pro cuticle not differentiates forms, old exocuticle gets shed
5) 24hrs differentiation occurs in pro cuticle
pleural membrane:
Joints at abdomen (soft)
melanisation:
chemical process cross linking involves melanin
Sclerotised
cross linking process can crosslink but is transparent (i.e. eyes)
chitin:
orientation of each secretion different to increase strength
cuticle function:
- mechanical protection
- supports body & provides surfaces for muscle attachment
- water retention & conservation
- active barrier against pathogens (and pesticides)
- location of colours for camouflage / courtship / aposematism