L5 the cuticle Flashcards
What are 5 functions of the cuticle
Mechanical protection
Prevents desiccation
Protective barier against bacteria, viruses and tocins
Location of colours and patterns important for behaviour
Supports body and provides points for muscle attachment via connecting tonofilaments
What is likely to be seen in cuticle shape at a point where muscle is attached
Infolding
What is the living layer od the cuticle made of
Epithelial cells resting on connective tissue
Where does the non-livign layer of the cuticle come from
Secreted from the epithelial cells during moulting
What are the layers of the non-living cuticle and where are they
Epicuticle - thin and on outside
Procuticle - inside
What are the layers of the non-living cuticle and where are they
Epicuticle - thin and on outside
Procuticle - inside
What are the 2 definite layers of the epicuticle
What is their structure
Inner and outer epicuticle
Inner - thicker, lipoprotein layer
Outer - very thin
What are the 2 potential additional layers of the epicuticle
What is their structure and goal
Wax layer - water retention, bipolar molecules (hydro phobic / phillic)
Cement layer - protect wax layer from heat or abrasion
What direction do neighbouring chitin chains run in
Opposite
What holds chitin together
H bonds
What do chitins come together to form
Microfibrils
How is chitin arranged
Forms fibrils which wrap w/ proteins and assemble in to fibre
Fibre assembles to bundles
How do bundles arrange themselves
Parallel to eachother
What is the name for what bundles arrange themselves into
Pseudolayers
What structure do the pseudolayers take on
Stack into helices, rotated ariund central axis
How do microfibril alternate their production - what are the 2 forms
Helicoidally arranged and uni-directional
What can limit growth of microfibril layers
Food supply
How are lamella arranged in helicoidal arrangement
Each layer (lamella) rotates anti-clockwise by fixed angle
How are lamellae organised in unidirection microfibril
Lamellate alternated with uniformly orientated microfibrils in same direction
Are soft cuticles more or less hydrophilic than hard cuticles
More
Where are proteins secreted from
Golgi apparatus
What molecules with a soft cuticle contain in higher proportions than a hard cuticle
Aspartic acid
Glutamic acid
Histidine
Lysine
Tyrosine
What kind of insects are likely to have undifferentiated procuticle and why
Holometabolous larval insects
Allows larva to remain extensible and facilitates intrastadial growth
Permits changes in body form
Conserves energy
What process results in a rigid cuticle
Tanning
What part of an insect is likley to be heavily tanned
Mandibles
Is tanning reversible
Irreversible - cannot be eaten or reabsorbed
What is tanning and how many methods of it are there
Cross-linking between proteins to form hard matrix
3
What are the processes of tanning and what is the end product
Quinone tanning = protein becomes lijked to quinone, cuticle darkens
B-sclerotinisation = protein linked to molecule, cuticle hard but colourless (e.g. Eyes)
Melanin = fills gaps in protein matrix, cuticle darkens and protects against UV, influences thermoreg
Where might a membranous cuticle be found
Between sclerites
In a membronous cuticle, is the procuticle tanned or untanned
Untanned
What determines the degree of moement in a membranous cuticle
Extent of membrane (size) and method of articulation (monocondylic or dicondylic)
Is formation of a membranous cuticle irriversible
No
Where is ecoscuticle absent
Ecdysial lines
What occurs at the ecdysial lines
Cuticle splits duting ecdysis
What protein is found in elastic / extensible cuticle
Resilin
How does resilin maintain elasticity
Amino acids form cross-links between protein chains whcih prevents other cross-linking
What minerals may be added in calcification
Calcite
Vaterite
Hydroxyapatite
Which insects is calcified procuticle found in and why
Immature insects
Calcification would make mature insects too heavy for flight
