Lecture 7: Cuticle

Question 1

Structure of the cuticle:

Answer 1

• Epidermis Basal lamina
• Procuticle; Endocuticle and exocuticle
• epicuticle

Question 2

are the endo and exo cuticle always the same ratios?

Answer 2

NO

-endo usually bigger but not necessarily

Question 3

the epistle structure ____ in insects

Answer 3

varies

Question 4

Epicuticle structure:

Answer 4

OUTSIDE

• cement layer
• superficial layer
• lipid monolayer
• -(wax canal starts continues through exocuticle where becomes pore canal)
• outer epicuticle
• inner epicuticle

Question 5

2 most important layers of epicuticle:

Answer 5

• cement layer

- lipid monolayer

Question 6

cement layer:

Answer 6

• shellac like proteins

- maintains integrity

Question 7

lipid monolayer:

Answer 7

• protects against water loss

Question 8

Procuticle: Exocuticle

Answer 8

• 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

Question 9

Procuticle: Endocuticle:

Answer 9

• 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

Question 10

Moulting steps:

Answer 10

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

Question 11

pleural membrane:

Answer 11

Joints at abdomen (soft)

Question 12

melanisation:

Answer 12

chemical process cross linking involves melanin

Question 13

Sclerotised

Answer 13

cross linking process can crosslink but is transparent (i.e. eyes)

Question 14

chitin:

Answer 14

orientation of each secretion different to increase strength

Question 15

cuticle function:

Answer 15

• 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

Question 16

aposematism:

Answer 16

warning colouration (wasps/ladybirds)

Question 17

consequences of cuticles material properties: - stiff & light

Answer 17

ideal for aerodynamic control surfaces (flight)

Question 18

consequences of cuticles material properties: hard

Answer 18

• ideal for mouthparts that enable a range of feeding strategies

Question 19

consequences of cuticles material properties: flexible and strong -

Answer 19

ideal for mobility. When coupled with hard exoskeleton plates it means a mobile

Question 20

consequences of cuticles material properties: high efficiency in kinetic energy storage

Answer 20

resign enables insects to make incredible springs for jumping, flying and pumping