Mosquito Larvae Change Their Feeding Behavior in Response to Kairomones From Some Predators

What is it about?

By pumping water containing predator kairomones into jars of mosquito larvae (so the predator itself was not present) changes in the larval feeding behaviour could be observed to see whether they changed from active swimming over the bottom scraping biofilms to the much more passive surface filter feeding. The objectives were first to see whether the larva was able to distinguish between different predator species and thus alter its response depending upon the risk that the predator posed. Secondly, to see whether the response differed from that of chopped up conspecifics producing alarm pheromones (and from controls of just water). Thirdly, to see whether the response varied depending on the age of the larva. In the mosquito Culiseta longiareolata, all instars reponded strongly by reducing bottom-feeding to kairomones from dragonfly nymphs, damselfly nymphs and the fish Aphanius dispar, but did not respond to the water scorpion (Nepa cineraria) - and Nepa could not be persuaded to feed on the mosquito larvae. 2nd and 3rd instar mosquito larvae produced a similar response to chopped mosquito larvae, but the 4th instars responded significantly stronger to the kairomones than to chopped larvae, so they appear to be more selective in their response. Active bottom feeding is more risky to the mosquito larva, since insect predators see movement more readily than an inactive surface feeder. In addition, bottom feeders are more accessible especially to dragonfly nymphs. Culex quinquefasciatus, however, did not respond to either predator kairomones or to damaged conspecifics. This is probably because its specialised habitat in highly polluted water results in a low predation risk, due to the lack of dissolved oxygen.

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Why is it important?

Biological control of mosquito pests using predators against the aquatic larvae would be most efficient if the mosquitoes were unable to detect the predators. If the mosquito larvae have developed strategies to reduce their predation risk, then the efficiency of the control method will be compromised and so it is important to know what are their strategies for coping with different types of predators.