Lecture 9: Senses

Question 1

light is perceived through __ of sense organs

Answer 1

a number

Question 2

_____ are the most important consist of a group units called ___

Answer 2

compound eyes

-ommatidia

Question 3

in ommatidium a lens..

Answer 3

• a lens focusses light onto the photoreceptor element and then the nerve goes directly into the brain
• enables insects to see UV and the plant of polarised light

Question 4

compound eyes appeareance

Answer 4

• pair bulge on each side of the head
• can be v reduced example flea
• reduced with individual facets
• or v large (dragonfly)

Question 5

Ommatidium structure:

Answer 5

TOP
-cuticular lens

• primary pigment centre: crystalline cone
• secondary pigment centre: Retinula cell and rhabdome

Question 6

ommatidium modifications

Answer 6

• eucone eye
• acone eye
• exocone eye

Question 7

Variation in Eucone eyes

Answer 7

• aposition
• -just day
• superposition
• -diurnal,active dawn &dusk as well as day

Question 8

cuticular lens is

Answer 8

sclerotised

Question 9

light collecting unit

Answer 9

rhabdome

Question 10

retinula cell is

Answer 10

transparent

Question 11

rhabdome consists of a series of stacked

Answer 11

microtubules

Question 12

acone eyes are only found in

Answer 12

apterygotes

Question 13

exocone eye

Answer 13

• massive lens

- nocturnal

Question 14

insect eyes have no ___ nerve

Answer 14

optic nerve, the eye goes straight into the optic lobe

Question 15

insects eye form a __ image

Answer 15

mosaic

-capable of v high resolution or v. good movement perception

Question 16

insect eye can resolve objects with an angular separation of

Answer 16

1 degree

Question 17

insect visual pigment is

Answer 17

retinin

Question 18

superposition eye is very __ sensitive

Answer 18

light, become dark-adapted

Question 19

insects have 2 sensitivity peaks

Answer 19

one in UV one in blue green

Question 20

Ocelli function

Answer 20

• inverted triangle on top of head
• a single lens but 2 or more rhabdomes
• v sensitive to diurnal change sin light levels
• control circadian rhythms & adjust pigment cell movement in superposition eyes

Question 21

stemmata:

Answer 21

• restricted to certain larval holomebolous
• laterally on head
• visual acuity is v low
• coarse mosaic image - detects dark shapes and movement

Question 22

mechanoreception

Answer 22

any mechanical distortion of the body

• touch, vibration, strain & stress
• huge range of sensitivity

Question 23

mechanoreception: trichoid sensilla

Answer 23

• hairlike
• in procuticle
• held in place by resilin loop
• tubular structure in cuticle is SCOLOPALE with nerve ending in it

Question 24

campaniform sensilla

Answer 24

detects distortion in cuticle (stress/strain)

• smaller hole in cuticle more pressure needed to distort, big hole = easier
• or by shape (oval)

Question 25

chemoreception

Answer 25

• trichoid sensilla as well
• smooth & groove
• groove = chemo ones
• abundant on antennae, mouthparts & legs
• nerve endings are exposed through holes in cuticle

Question 26

2 types of chemoreception

Answer 26

• gas phase - olfaction

- liquid phase - contact chemoreception

Question 27

thermal & hygro reception

Answer 27

• water balance & temp important for insects
• v little about these receptors, no temp receptors identified
• identified by ablation experiments