insect cuticle Flashcards
what are the roles of the insect cuticle
- protection from predators and dessiccation
- provides shape and support to soft tissues
- protection from attack or injury
- first line of defence against pathogens
- minimise the loss of body fluids
what are the functions of the cuticle
- Mechanical protection
- Prevents desiccation
- Protective barrier against bacteria, viruses, toxins
- Location of colours and patterns important in
behaviour - Lines:
a) External surface of the body
b) Tracheae
c) Anterior and posterior sections of alimentary
canal
d) Parts of the reproductive system
how does the insect cuticle support the body and provide points for muscle attachments
muscles which act on the exoskeleton are connected to the basal surfcae of epidermal cells through structurs called desmosomes
= muscular forces are transferred through these cells by microtubules running parallel from the bottom to top of the cells where they attatch to tonofilaments which run through the epidermal cells
what is an apodeme
refers to the internal ridge or process in the exoskeleton of insects
= serve as attachment sites for muscles providing structural support and facilitating movement
why can insects have more muscles, despite their size, compared to vertebrates
the exoskeleton has a larger surface area compared to an endoskseleton with alot more areas for muscle attachement
= having so many areas for muscles to attach allows increased leverage for appendages which is why insects are so much stronger
briefly outline the structure of an insect cuticle
consists of both living and non living layers- from outside in
1) epicuticle made up of
- cement layer
- wax layer
- outer epicuticle
- inner epicuticle
2) procuticle made up of
- exocuticle
- endocuticle
3) living epidermal cells
outline the structure of the living layer of the insect cuticle
rows of epithelial cells resting on connective tissues- forms basement membrane for the rest of the cuticle to sit
= cells secrete the non-living layers of cuticle during moulting
= other cells are interspersed in these epithelia cells and form sensory structures such as setae and hairs
outline the structure of the non-living layers of the insect cutcile
consists of two main layers - thin epicuticle and thicker inner procuticle
1) epicuticle - made up of addition 4 layers
- inner epicuticle = lipoprotein layer
- outer epicuticle
- wax layer = fragile but needed for water retention
- cement layer= protects the wax layer
outline the structure and function of the cement layer
can be absent in some insects
= thin layer which is found above the wax layer and produced by dermal glands
= consists of tanned proteins and lipids causing a hard shellac like substance
= protects against abrasion and isnt replaced if it is abraded until the next moult
outline the structure and function of the wax layer
varies in composition in different insects
- contains fatty acids, hydrocarbons and alcohols
= lipids are synthesised by oenocytes (specalised cells in the insect body) and transported by pore canals
= wax is transported to the surface of the insect via these pore canals
= change permeability of the cuticle to water
outline the structure and function of pore canals
= cytoplasmic extensions of epidermal cells which transport cuticular materials to the surface
= occur in large numbers
= shape probably determined by the orientation of fibres making up lamellae in the endocuticle
what is the inner procuticle made up of
consists of two layers
1) Exocuticle = dark, outer layer
2) Endocuticle = pale, inner layer
outline the constituents of the epicuticle
the outer epicuticle (3/4 layers) contains no chitin
the outer layer = made up of non-elastic lipids and proteins
the inner layer = made up of tanned lipoproteins
outline the constituents of the procuticle
the inner cuticle (2 layers) has chitin
= first secreted as procuticle before the outer is sclerotised exocuticle and the inner is left undifferentiated endocuticle
outline the structure of chitin
- Polymer of N-acetylglucosamine
- Makes up 20-50% dry weight of
procuticle - Neighbouring chains run in
opposite directions - Held together by H-bonds
- Form microfibrils (Ø = 2.8 nm)
- Embedded in protein matrix
(reinforced concrete)
