Atlant’s Column: The More Harmless Mosquito

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Welcome to the section on Micronaut.ch which explores, analyzes and explains fascinating microscopical structures.

Mosquito egg surfaceMosquitoes are despised as transmitters of diseases. But they also have a peaceful side. As larvae, they sweep the surface of ponds and lakes with their mouth brushes.

The mosquito Anopheles gambiae is one of the most important transmitters of malaria If it bores into the bloodstream of a human with its proboscis, it can take up the pathogen and then pass it on countless times. Every year, over a million people die from malaria infections.

But in its life, the mosquito not always appears as a killer. In its youth, it is a rather gentle and harmless creature. In this so-called larval stage, it resembles a worm that lives in stagnant water such as lakes, ponds, ditches, clogged roof angels, or bird baths.

There, it consumes no blood, but rather lives of what others do not need anymore: dust. Every water surface is a collector of pollen and tiny particles originating from plants and animals. From this pile of garbage the larva feeds. In order to do this, it wipes the water surface with its mouth brushes.

 

 

Scanning electron microscope image of mosquito larva (family Culicidae) mouth parts.The Undulating ‘Micro-Feather-Duster-Machine’ – Technological Masterpiece Without Patent Protection

 The brushes are two structures that look like feather dusters on each side of the mouth. Its bristles are shown in this image (see at left).

But the goodies don’t come for free. The larva must do a fair bit of acrobatics in order to get them. Its handicap is that it must float with its back stuck to the water surface. Only in this position the breathing holes on its back break through the surface and suck in air. But with its head pointing downwards rather than upwards, brushing becomes rather difficult. The solution to this problem, however, is simple. The larva turns its head 180 degrees like an owl. Now the mouth brushes can reach the surface easily and finally begin their work. By constant fanning, they produce a weak water flow, which washes the particles directly in front of the mouth of the larva.

With this mostly vegetarian diet, it takes two weeks until the larva reaches its pupal stage. Later, the adult female cannot go on in such a leisurely pace anymore while producing her eggs. Hundreds of them have to mature in her body within weeks. In order to achieve this before her natural death arises, she changes to a much more nutritious and efficient kind of food: blood.

Further reading:

Biology and life cycle of mosquitoes

Feeding mosquito larva

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Continue reading Atlant’s Column: Blind flight of the genes , February 2014, or go back to the archive