L11 Olfaction - Rebecca Pike

Question 1

Why do aphids emit a scent when attacked by ladybirds?

Answer 1

Alarm pheromone to warn others, but also attracts other ladybirds.
Shows the olfactory sense can be multifunctioning.

Question 2

Give an example of multifunctional olfactory cues.

How is this an example of coevolution?

Answer 2

Tritrophic interactions
Caterpillar eats plant, plant releases chemicals to harm caterpillar and deterrence.
Some caterpillars resistant to plant so plant also releases volatiles, which attract parasitoid wasps to parasitise caterpillars.
Maybe originally volatiles had a different function, but attracting wasps proved beneficial to plant and wasps.

Question 3

What are 3 functions of plant volatiles?

Answer 3

Attract more herbivores (bad for plant)
Repel other herbivores
Attract parasitoids

Question 4

Give an example of a family where olfaction may be more important than sight

Answer 4

Phoridae - flies
One species has funicula grown right over the eye
Perhaps allows airflow over the sensors more easily, or olfaction is more important than sight.

Question 5

What is Bombyx mori what is their main sensory organ?

Answer 5

Silk moth
very sensitive antennae structurally similar to feathers. Contain olfactory and mechanosensory receptors. each antenna has 10-20 flagellomeres, covered in filiform hairs. aerodynamic so max airflow over hairs.
1 molecule is the quantum limit (smallest amount they can detect)

Question 6

How do male silk moths find the females?

Answer 6

Females pass scent in clumps, which spread out with distance from female.
In order to find female, male has to fly laterally upwind and can sense on/off patterns of pheromone. When absence of pheromone detected for a while, he turns. turns more frequently when closer to female and pheromone at much higher concentration.

Question 7

What are 6 types of olfactory receptors?

Answer 7

1. Sensille trichoidea - similar to mechano tricois sensilla but much longer, in silk moths. Large SA
2. s. basiconica - Shorter and more cone chaped. very small, in drosophila Dendrites cannot be open to air as they dessicate, so are packed closely to cuticle wall next to pores instead.
3. S. coeleconica - similar to basiconica but in a cavity
4. S. ampulacea - similar to s. coeleconica but unsure of function
5. S. placodea - no hairs, v unusual semicircular detection plate made of radii with different olfactory pores.
6. Sensilla in a field formation - in carrion flies, multipliesneurones and SA internally.

Question 8

What olfactory receptors do bees have?

Answer 8

Basionic and placodonic types neatly arranged and closely packed to increase efficiency. Up to 400 on each arista.

Question 9

What olfactory receptors does Drosophila have?

Answer 9

Basiconic, trichoid and coeloconic types on the antenna and just basiconic on the maxillary palps.

Question 10

How are mosquito antenna adapted?

Answer 10

Can measure CO2 and warmth, as prey releases CO2 and Warmth.

Question 11

How can you study olfaction?

Answer 11

1. insert the odour eg insect pheromones into gas chromatograph, splitting it into a detector and alto onto antennae.
2. in detector, it gives FID reading to show the composition of the odour.
3. Electrodes in the antenna give EAD reading. Can match up peaks to see which molecules the antenna is responsive to.

Question 12

describe the olfaction pathway

Answer 12

Receptor neurones of different types separate out and connect onto different glomeruli (massive balls of cells)- eg Cumulus or Toroid. Interneurones connect the glomeruli to regulate and mask different smells.
Glimeruli connect to mushroom bodies by Principle output neurones.

Question 13

How can glomerulii be imaged?

Answer 13

Calcium imaging maps to view the response of each cell, and see the activity of neurones.