Tiny fly can keep dengue-causing mosquito in check

June 5th, 2009 - 3:01 pm ICT by IANS  

Washington, June 5 (IANS) The larvae of a tiny fly or midge can help decimate a number of invasive Asian tiger mosquitoes, that infect 50 to 100 million people with dengue fever every year in the tropics.
Once found only in tropical and sub-tropical regions of Southeast Asia, the Asian tiger

mosquito has now spread to Africa, the Americas, Australia, the Caribbean, Europe and the Middle East.

Midge larvae do not harm native mosquitoes, helping them survive, even though the invasive mosquitoes are better at gobbling up resources.

The researchers found inherent size differences between the mosquito species. The

tree hole (native) mosquito is larger than the Asian tiger mosquito, which makes it less vulnerable to predation from the small but voracious predatory midge.

Previous studies have found that the native mosquito larvae also adopt less “risky”

behaviours than the invasive mosquito larvae, making them less susceptible to being eaten.

“Size is having a major effect in terms of how the prey are getting consumed,” said Barry Alto, medical entomologist with the State Natural History Survey at the University of Illinois (U of I).

“This is another mechanism that allows the native mosquito to hang on and co-exist with the invasive mosquitoes in certain areas where predators are present,” Alto said.

The Asian tiger mosquito was first detected in the US in 1985 in a shipment of used tyres to a Texas port. Like the native mosquito, it lays its eggs in watery containers, including tyres.

Even if the water evaporates, a splash of rain and a supply of nutrients such as the microbes that feed on dead leaves are all that the larvae need to hatch and grow.

Like the yellow fever mosquito (Aedes aegypti), another invasive mosquito that

is now well established in the Americas, the Asian tiger mosquito can carry several viral diseases that afflict humans.

The interaction between predators and native and invasive mosquitoes is one of several

factors that may contribute to disease transmission, Alto said, according to a U of I release.

These findings were published in the British Ecological Society’s Journal of Animal Ecology.

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