More mosquito

Question 1

What organ detects nectar?

Answer 1

The labium.

Question 2

What organ detects blood?

Answer 2

The stylet.

Question 3

Where are neurons located in the stylet?

Answer 3

They are located in the part of the stylet known as the labrum.

Question 4

What parts of the stylet pierce the skin and come in contact with the blood?

Answer 4

All parts of the stylet, including the labrum,
maxillae, mandibles, and hypopharynx, pierce the skin and
directly contact blood, but the labrum is the only innervated
part of the stylet.

Question 5

How many eggs do mosquitoes produce per blood meal?

Answer 5

Females typically take small nectar meals but
engorge on blood, consuming a volume that approximately doubles their body weight and provides sufficient protein to allow
them to produce 100–150 eggs per blood meal.

Question 6

What happen if the blood meal is replaced with nectar sugars in the presence of the human cues heat and CO2?

Answer 6

The females reject the meal entirely.

Question 7

Summarize Jove:

Answer 7

• Using pan-neuronal GCaMP calcium imaging, we found
  that stylet neurons respond robustly to blood and its components but are insensitive to nectar-specific sugars.
• A mixture of four blood components—adenosine triphosphate, glucose, sodium bicarbonate, and sodium chloride— that has been shown previously to potently trigger blood-feeding behavior (Galun
  et al., 1963, 1984; Hosoi, 1959) activated the same population of stylet neurons as blood.
• We identified Ir7a and Ir7f
  as female stylet-specific transcripts and generated driver lines
  for both genes using CRISPR-Cas9 genome editing. We found
  that each driver line labels a functionally distinct subset of
  blood-sensitive stylet neurons activated by different components of blood.
• Finally, we discovered polymodal stylet ‘‘integrator’’ neurons that respond to physiological levels of blood
  glucose only in the presence of additional blood components.
  Importantly, all stylet neurons, including integrator neurons, are
  not activated by high concentrations of nectar-specific sugars.

Question 8

Explain what happens when a female mosquito bites a human

Answer 8

she retracts the labium, uncovering the needle-like stylet required to draw blood. During
blood feeding, the stylet pierces the skin to come into direct contact with blood. In contrast, the labium rests on the skin’s surface, which prevents it from contacting blood. During nectar feeding, the
labium directly contacts the nectar source, and the stylet remains recessed and ensheathed in the labium

Question 9

What is the average blood meal size of a female?

Answer 9

3.20 mL in stark contrast to the
average sugar meal size of 0.87 mL

Question 10

Does changing the concentration of ATP alter the probability of initiating engorgement?

Answer 10

Yes, but did not affect the meal size (Jove)

Question 11

Where do stylet neurons project?

Answer 11

stylet innervation was restricted to a discrete anterior and ventral region in the subesophageal zone. The female labium projects to the posterior
region of the subesophageal zone, and there is no overlap with stylet neuron projections. Therefore, inputs from the stylet and labium are segregated
at the first synapse in the subesophageal zone.

Question 12

How many “clusters” of responsive neurons are there in the stylet that respond to components of whole blood?

Answer 12

5

Question 13

Describe the expression of Ir7a and Ir7f

Answer 13

Ir7a and Ir7f are expressed in approximately 1–2 neurons
and 3–4 neurons, respectively. No expression of either gene
was detected in male stylets. The sparse nature of these drivers
revealed dendritic innervation of the bilaterally symmetric set of
two chemosensory sensilla at the stylet tip

Question 14

What do Ir7f and Ir7a respond to?

Answer 14

Ir7a- and Ir7f-expressing blood-responsive populations respond to Mix (glucose, NaHCO3, and NaCl) but not ATP Ir7a blood-sensitive neurons were
robustly activated by NaHCO3 (Figures 6I and 6J), sharing a profile with NaHCO3 neurons identified in cluster 2 (Figures 5G–5I).
In contrast, Ir7f blood-sensitive neurons were consistently activated by Mix and had variable responses to 140 mM NaCl
and/or 25 mM NaHCO3

Question 15

What do the “integrator” neuron in the stylet respond to?

Answer 15

We directly observed integration by a subset of stylet neurons maximally activated by co-presentation of glucose, NaCl, and NaHCO3

Question 16

In Magurie_Potter (2022) what does AnGamOR2 respond to?

Answer 16

To test this, we expressed A. gambiae OR 2
(AgOR2) in all ORCO+ ORNs. AgOR2 is highly attuned to major
components of human and animal odors such as benzaldehyde and indole.

Question 17

Summary of Maguire_Potter:

Answer 17

Expressed ORCO+ AgOR2
1) Surprisingly, when we evaluated the olfactory physiology of these experimental mosquitoes, we found that they exhibited reduced responses not only to the cognate ligands of AgOR2 (benzaldehyde and indole) but also to odorants in general.
-Using RNA sequencing (RNA-seq) to compare transcript levels
from wild-type antennae to those ectopically expressing
AgOR2, we discovered that A. gambiae OR isoforms were significantly downregulated in the experimental line, while the remaining transcripts were largely unchanged.
-OR2 protein rather than mRNA is needed to reduce OR levels
- Overall, our study suggests that an OR-mediated feedback mechanism exists that can regulate A. gambiae OR expression.

Question 18

Matthews ppk301 summary:

Answer 18

We found that the DEG/ENaC channel ppk301 and sensory neurons expressing ppk301 control egg-laying initiation and choice in Ae. aegypti. Using calcium imaging, we found that ppk301-expressing cells show ppk301-dependent responses to water but, unexpectedly, also respond to salt in a ppk301-independent fashion. This suggests that ppk301 is instructive for egg-laying at low-salt concentrations, but that a ppk301-independent pathway is responsible for inhibiting egg-laying at high-salt concentrations. Water is a key resource for insect survival and understanding how mosquitoes interact with water to control different behaviors is an opportunity to study the evolution of chemosensory systems.

Question 19

What happen to offspring if the water in which eggs are laid is too salty?

Answer 19

Offspring will die.

Question 20

What does a mosquito use to locate water at distance?

Answer 20

A female Ae. aegypti mosquito with a fully developed batch of eggs will use elevated humidity and bacterial volatiles to locate water at a distance.

Question 21

What cues does a mosquito use upon contact with a body of water?

Answer 21

Once in close-range, a mosquito contacts water to evaluate its suitability for egg-laying by sensing a wide variety of cues that include salinity, food, bitter toxins, and animal-derived chemical signals indicating the density of conspecific larvae and pupae or the presence of predators

Question 22

What salinity do Mosquito avoid laying eggs in?

Answer 22

Mosquitoes showed no significant preference between deionized water and dilute seawater up to 10%, with individual mosquitoes either picking a solution at random or distributing their eggs between both solutions (Figure 1D). However, they showed a strong dose-dependent aversion to higher concentrations of seawater, with an IC50 of 12.25% seawater (Figure 1D,E). Females showed near-complete aversion to 25–100% seawater (Figure 1D,E). These choices have consequences for the offspring. When we measured survival of offspring reared in varying concentrations of seawater, we found dose-dependent lethality (LD50 = 25.23%) (Figure 1E). To simplify the stimulus, we used sodium chloride (NaCl), the predominant salt in artificial seawater, in all subsequent experiments. Females showed dose-dependent inhibition of egg-laying with increasing concentrations of NaCl (Figure 1F) when they were only given access to a single concentration, suggesting that the preference for freshwater may be driven in part by an aversion to laying eggs in saltwater. Similar to artificial seawater, NaCl produced a dose-dependent decrease in offspring survival.

Question 23

What do parasitic wasps use to locate prey (Carnaghi_Hawks, 2021)?

Answer 23

They use vibrational and visual cues.

Question 24

List the findings by Carnaghi_Hawks (2024) Landing on heating targets:

Answer 24

• Landing rate is directly proportional to the surface are of thermal stimulus whereas close range orientation is modulate by both thermal and visual inputs. we found that targets with a larger proportion of heated surface area are significantly more attractive.
• large visual targets are both preferred by mosquitoes and induce more frequent landing than small visual targets but catch fewer mosquitoes per unit area.
  Tracks recorded around vertical targets were significantly more tortuous compared to tracks recorded around horizontal targets.
  -target size is directlyproportional to the distance at which it is resolved, with larger targets resolved at a considerably greater distance than smaller targets, whiletargets with comparable sizes are detected further away if oriented vertically rather than horizontally.

Question 25

Describe Drosophila deceleration prior to landing: (Carnaghi_Hawkes, 2024).

Answer 25

In [[Drosophila]] #deceleration prior to landing is triggered by a combination of absolute target size and its rate of visual expansion over the retina but in at least one species of stingless bee, Scaptotrigona depilis, very small targets initiate an unusual accellerated landing strategy.

Question 26

Describe the biting sites distribution of Anopheles mosquitoes (Carnaghi Hawkes, 2024).

Answer 26

Previous studies that used live human baits reported that the biting sitesof Anopheles mosquitoes were species-specific and depended on the spatial orientation of the host, with more bites received onthe legs and feet in standing hosts, whereas when hosts were lying flat on the ground, bites occurred across body parts closestto the ground.