Sensory systems & communication II

Question 1

insect vision

Answer 1

• ocelli
• compound eye
• superposition compound eye
• apposition compound eye

Question 2

insect vision - ocelli

Answer 2

• on top of the head in groups of 3
• sense light levels and horizon (which way is up) when flying

Question 3

insect vision - compound eye structure

Answer 3

• ommatidium
• rhabdom

Question 4

insect vision: compound eye - ommatidium

Answer 4

• Each facet in the compound eye
• Pigment on sides means each ommatidium ‘sees’ only small slice of visual field
• More facets = higher resolution of vision

Question 5

insect vision: compound eye - rhabdom

Answer 5

• Rhabdom are photoreceptors that converge to optic nerves
• the brain then constructs image from individual inputs

Question 6

insect vision - superposition eye

Answer 6

• sacrifice resolution for increased light
• used by nocturnal insects

Question 7

insect vision - apposition eye

Answer 7

• high resolution, but only when there is enough light
• Not used by nocturnal insects

Question 8

What does an insect see?

Answer 8

• Insect spectrum is shifted
• Flicker-fusion rate
• see polarized light

Question 9

what does an insect see? - insect spectrum

Answer 9

• insects see weak in red (except Lepidoptera – they see red) but strong in UV
• Implications for sexual signaling and flower design
• Insects see color AND UV – not either/or

Question 10

what does an insect see? - flicker-fusion rate

Answer 10

• a measure of temporal resolution of vision
• Humans see ~ 60 frames per second
• insects see ~ 200-300

Question 11

what does an insect see: flicker-fusion rate - why is it so fast

Answer 11

• flight
• Means that an insect can see and react to motion before we even notice that an object is moving

Question 12

define Bioluminescence

Answer 12

• Light production
• Fireflies (beetles – Lampyridae): males use light signal for females (mating)

Question 13

Why do insects fly to lights?

Answer 13

• Sky is brightest part of environment, even at night and it keep insects right-side up when flying
• But artificial lights overwhelm the night sky, insects tilt towards them, hijacks navigation ability

Question 14

why do insects fly to lights? - prediction and result of experiment

Answer 14

• prediction: diffuse light from above should not interfere with flight bc it’s the sky
• result: This prediction is met

Question 15

define Chemoreception

Answer 15

sense of smell

Question 16

Chemoreception - where is it located

Answer 16

• Multi-porous sensilla
• Pore kettle
• Odorant binding proteins (OBP)
• antenna

Question 17

chemoreception - multi-porous sensilla

Answer 17

basic sensory unit for chemoreception

Question 18

chemoreception - pore kettle

Answer 18

• at each pore, tubules connect with dendrites
• Pores let molecules in through cuticle

Question 19

chemoreception - odorant binding proteins

Answer 19

• they bind with chemical molecules to depolarize dendrite and it stimulates the neuron
• Specificity of OBP determines specificity of chemoreception

Question 20

chemoreception - antenna

Answer 20

• Multi-pore sensilla are concentrated on the antenna
• Larger antennal surface area -> more sensilla -> more sensitivity to chemoreception

Question 21

chemoreception - Often males have elaborated antenna. Why?

Answer 21

It’s most likely a species where female releases sex hormone, so males are selected to sense them

Question 22

define pheromones

Answer 22

• Chemicals signals to influence behavior of receiver
• this is not just smelling other insect, but detecting chemical message sent by them

Question 23

pheromones - typical examples

Answer 23

• Spacing
• Aggregation
• Alarm, especially social bees and ants
• sex pheromones

Question 24

pheromones - atypical examples

Answer 24

• Thymine wasp and orchid
• lycaenid (Lepidoptera) caterpillars and ants

Question 25

pheromones - thymine wasp and orchid

Answer 25

• Thymine wasp: flightless female summons male with sex pheromone, he mates with her
• An orchid mimic both shape and pheromone of female: male lands, get pollen stuck on his back (results in pollination of next flower)

Question 26

pheromones - lycaenid caterpillars and ants

Answer 26

• Some lycaenid (Lepidoptera) caterpillars mimic surface chemicals of ant larvae
• Ant carries them back, feeds them, caterpillars pupate in ant nest

Question 27

define sex pheromones

Answer 27

• Usually females advertising presence and fertility; attract male mate
• Can be extremely effective and there is an opportunity for use in pest control

Question 28

sex pheromones - How does male find way?

Answer 28

the male follows concentration gradient

Question 29

sex pheromones - pest control uses

Answer 29

1. monitoring (are insects around?), bait for traps
2. mating disruption

Question 30

sex pheromones: pest control - advantage

Answer 30

specific – don’t have to kill other insects

Question 31

sex pheromones: pest control - disadvantage

Answer 31

maybe expensive to make, may not be known

Question 32

pheromones - How do we know what chemicals are pheromones, what their composition is?

Answer 32

GC-EAD (Gas Chromatograph– Electro-Antenographic Detector)

Question 33

pheromones - GC-EAD

Answer 33

half of sample goes to GC for chem analysis, half to EAD to test if it triggers neural response

Question 34

pheromones: GC-EAD - disadvantages

Answer 34

1. measures SUMMED response of antenna, not individual sensilla
2. removed antennae functions for a while after removal
3. neurons firing not the same as behavioral response