Rhythms and gonotrophic cycles

Question 1

What does the gonotrophic cycle consist of?

Answer 1

Blood feeding, egg production and laying/oviposition.

Takes 2-3 days.

Question 2

What are the circadian activity rhythms?

Answer 2

The flight activity rhythms. 12hr:12hr light:dark

If night flyer and you switch lights on for 3 days there is no flight activity vice versa. -Phase setting effect.

Question 3

Why is male and female mosquito activity synchronised?

Answer 3

To coordinate mating, evening activity of the female is associated with male swarming when they will lek to attract females into the swarm.

Question 4

How does the male know where the female is?

Answer 4

Its antennae acts like an ear with thread structures that resonate to female sound of whine from wing beat.

Question 5

What happens to the anopheles female behaviour after mating?

Answer 5

Switch from mate seeking to host seeking behaviour due to the MAG pheromone from the male, so the evening activity peak is reduced and activity occurs later in the dark phase

Question 6

What happens to anopheles female behaviour when blood fed and inseminated?

Answer 6

Reduced activity for two days while blood digests and eggs develop.
Then searches for oviposition site so evening activity peak increases again.

Question 7

What is a nulliparous mosquito?

Answer 7

One that has never taken a blood feed.

Question 8

What is a parous mosquito?

Answer 8

One that has had at least one blood feed before.

Question 9

What is the behaviour of a parous anopheles mosquito?

Answer 9

It goes back to host seeking, as it only mates once. So late evening peak in dark phase.

Question 10

Why do female anopheles only mate once?

Answer 10

Because the male accessory gland (MAG) secretion from the seminal fluid is now absorbed into the females heamolymph and changes the female behaviour to host seeking.

Question 11

What does the ecydsone do?

Answer 11

It is a hormone from the ovary that stimulates egg production and oviposition.

Question 12

What do midgut stretch receptors control?

Answer 12

Blood feeding activity.

Question 13

How does moonlight affect mosquito behaviour?

Answer 13

Higher catches when there was a full moon, suggesting increased biting patterns when there was more moonlight.

Question 14

When do Aedes aegypti fly and bite?

Answer 14

Day time flyers. Bite early morning and late afternoon.

Question 15

Why are both sexes of Aedes aegypti attracted to the host?

Answer 15

Males congregate around the host to find a female, as virgin females bite and feed. So mating and feeding sites are in vicinity of host, unlike anopheles.

Question 16

How do inseminated Aedes mosquitoes differ from Anopheles?

Answer 16

Aedes are less active when inseminated as they passively respond to host odour and wait for a host to pass due to peri-domestic habitats. But anopheles actively seek host when inseminated.

Question 17

Describe the process of parasite development in the mosquito

Answer 17

Uptake gametocyte in blood feed.
Gametocyte undergoes morphological change in midgut so it is capable of fertilisation.
Ookinete produced and multiplies and develops an oocyst.
Invasion of gut wall and oocyst maturation and rupture producing sporozoites.
Sporozoites into salivary gland.

Question 18

How long does the parasite development process take?

Answer 18

10 days.

Question 19

How does plasmodium infection affect flight activity?

Answer 19

Low activity when blood is digested, this maybe because the blood meal is low quality.
Reduced activity again at day 10 when mature oocysts rupture, and low activity when sporozoite infects salivary gland. This may be due to competition for nutrients, or damage to midgut/salivary gland.

Question 20

Brugian filariae (elephantiasis) in mosquitoes: How does the microfilariae infection affect the mosquito activity?

Answer 20

The microfilariae penetrate flight muscles in the thorax where it develops.
Flight activity is low for 2 days after feed when muscle is being penetrated, then returns to normal.
Another sudden permanent reduction in activity when L3 larvae form migrates from the muscle to proboscis.
Damage to the flight muscle if heavily parasitised.

Question 21

How does increased probing increase transmission?

Answer 21

The insects probe more and blood feed less readily so there are multiple host feeds because of blockages etc that mean the insect is not taking full blood meal, so moves to another host to get more feed.

Question 22

How do insecticide resistant genes affect mosquito behaviour?

Answer 22

The mutation for resistance changes the structure of chloride channels in the nervous system, so resistant mosquitoes need more stimulation and are less active.
The evening peak is later and they do not respond to moonlight in the same way.
So they may be less fit in an insecticide free environment.