Mechanoreception, chemoreception and thermal and hygroreception

Question 1

Mechanoreception

Answer 1

Perception of any mechanical distortion of the body
•touch, vibration, strain and stress
•can generate a huge range of sensitivities to touch
•hair-like cuticular spike known as a trichoid sensilla
-many functions from one sensilla

Question 2

Trichoid sensilla structure

Answer 2

•procuticle has hole where inner surface of hole has a ring of resilin attached
•also a hardened cuticular peg inside (beneath ring)
•inside hole is hollow cuticular hair - held in place by loop
-thicker cuticle = less resilin, so harder to push hair out of place
•scolopale sits closely to peg, inside hair
•inside has nerve ending - if moved will be simulated (depending on position of scolopale inside hair can cause directional sensitivity)
•scolopale will pinch nerve when moved

Question 3

Modifications to trichoid sensilla

Answer 3

• sensitive in all directions by having hair in loop shape - whichever way its bent the nerve fires
• more or less sensitive by having shorter or longer hair, heavier or lighter or make ring around hair rubbery or hard

Question 4

Campaniform sensilla

Answer 4

•important in detecting thoracic cuticle distortions
•flat unlike hairs
•hole covered by dome of cuticle attached to scolopale - filling in the whole is block of resilin
-nerve inside scolopale
•responsible for detecting distortion on cuticle
-pressure on dome = resilin pushed, squashing the scolopale and nerve

Question 5

Modifications to camapniform sensilla

Answer 5

•can make directionally sensitive and change distortion needed to fire (ovoid shape = easier to distort one way)
•can make the hole in the cuticle different sizes
-smaller needs more force etc.
•can change nature of resilin
•change size or thickness of scolopale

Question 6

Chemoreception

Answer 6

Controlled by trichoid sensillas
•grooved forms are more receptive to chemical stimuli
•abundant on antennae, mouth parts and legs
•nerve ending go to tips of hair - not just in scolopale
-cuticle has little holes where nerve endings exposed

Question 7

Types of chemoreception

Answer 7

1. Gas phase - olfaction (like smell)

2. Liquid phase - contact chemoreception (like taste)

Question 8

Thermal and hygroreception

Answer 8

•temp and humidity detection
•water balance and temp are linked and important to insects
•detected through cuticle - not sure how completely…
investigated with ablation experiments

Question 9

Ablation experiments

Answer 9

• if you shave off hair-like structures from antennae then they lose abilities in hygroreception
• no temp receptors identified
• can use these to find where receptors are located