Insect chemical ecology and olfaction Flashcards

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1
Q

What do EAG and SSR stand for?

A

Electroanennography and single sensillum recording. Two lab techniques often deployed together.

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2
Q

Name some techniques we can use for mosquito surveillance.

A
  • Human landing catches
  • Larval collections
  • Traps e.g. CDC augmented with chemicals.
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3
Q

HOw are the malaria vectors in SE Asia and S America different to those in Africa?

A

Are day biting and outdoor biting

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4
Q

What is a semiochemical?

A

A behaviour modifying chemical. Modifys the behavior of the recipient.

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5
Q

What is a chyromone?

A

A semiochemical that benefits the recievere but not the emitter.

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6
Q

What are the four stages of vector life where semiochemicals are involved?

A

When looking for:

  • A blood host
  • Nectar/ sugar meal
  • To oviposit
  • To mate
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7
Q

How is an olfactometer used in the lab? What are the benefits and disadvantages?

A

For rapid screening of attractants.
Benefits: reduces bias and allows standardisation
Disadvantages: may not represent natural conditoins as only the compounds of interested are separated out whereas naturally it is like a soup of odours.

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8
Q

WHy should insects never be reused in an assay?

A

They may learn, get used to a smell or become habituated (receptors switch off).

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9
Q

What is an olfactometer y tube? What is a disadvantae of this method?

A

A y shaped tube where insects are released at one end and choose which arm to go down- studies if they are attracted to a stimulus. Outcome can be measured by how many start probing as an indication of blood feeding.

Does not work as well with anopheles as they prefer a fine odour plume which is not given in this Y tube

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10
Q

What are videos of insects flying useful for?

A

Measuring a 3D flight patter is useful to inform traps.

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11
Q

How do anopheles fly?

A

Use a casting flight behaviour where they fly at 45˚ until they leave the odour plume and turns back and keeps repeating until they get to a narrow source of the plume

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12
Q

What equipment can be used for walking rather than flying insects? Give examples.

A

Still air olfactometers (dont need to use air flow as they are on the ground).
E.g. bedbug faeces in a pot as a pheromone cue.

Alternatively a servosphere which is a ball that moves as the insect walks and its movement pattern can be traced in response to a stimulus.

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13
Q

Describe two ways you can extract volatiles.

A

Solvent extraction
-fibre and swab skin

Air entrainment
-Clean air using a charcoal filter and pump. Air passed over a polymer so odours become trapped

Getting the ratio, concentration and combination of chemicals is important!

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14
Q

What is an SSR

A

Single sensillum recording.

Electrode attached to antenna and use an electroantennagram to see peaks in electrical activity in response to smell.

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15
Q

What are sensilla?

A

Small hairs on the antennae which serve an olfactory purpose and have olfactory receptors at the base of them.

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16
Q

How is gas chromatography useful for studying olfaction?

A

Allows the separation of gases based on their size. Can combine with an electroantennaegram.
Odours get split and half is burnt for chemical analysis and half is used for an odour stream to see how much the insect is responding to that cue.

17
Q

How can we test extracted chemicals behaviourally?

A

Test individual chemicals to see if they have the same effect as the natural source.

18
Q

What do twin studies show about attractiveness? How is this further supported?

A

Show high levels of heritability of attractiveness. Questionnaires also suggest the same, showing that parents that rarely get bitten are likely to have children who also rarely get bitten.

19
Q

Which chemicals are associated with infection and parasite stage? How was a study conducted?

A

Mainly aldehydes associated such as octanal and heptanal.
Infected asymptomatic Pf children in a tent and mosquitos collected. Showed that as the disease progressed there was increased mosquito attractiveness but this trend was not present post treatment.