May 20, 2022 1:00 pm

This is how ghost mosquito larvae float without sinking

In the spring of 2018, the zoologist Philip Matthews spent a typical afternoon capturing dragonflies in the experimental ponds at the University of British Columbia (UBC) in western Canada. While working, he was particularly struck by a few larvae floating on rainwater from a cattle trough not far away.

Unintentionally, the researcher has solved an entomological mystery that had been intriguing the scientific community for more than 100 years

He didn’t know it at the time, but he was inadvertently going to embark on a journey that has allowed him to solve an entomological mystery that had been intriguing the scientific community for more than 100 years. Freshwater larvae of the genus Chaoborus, found in the water tank, belonged to the one known as ghost mosquito, for being almost transparent.

“These strange insects floated neutrally [sin elevarse ni hundirse] in the water, something you don’t see other insects do,” says Matthews. “Some can reach neutral buoyancy for a short time during a dive, but the larvae of Chaoborus they seem to be the only insects that can do it,” he continues.

In fact, in 1911, the Nobel Prize August Krogh discovered that these larvae use an entirely different mechanism, regulating their buoyancy by two pairs of internal air-filled sacs. However, he never found out how they adjusted the volume of these bags without having blood or hemoglobin like vertebrates.

In the case of fishFor example, some species regulate their buoyancy by inflating a swim bladder with oxygen discharged from the hemoglobin in their blood.

The blue fluorescence of the air sac is due to resilin. / Philip Matthews

A chance discovery

Returning to his lab, Matthews observed the air sacs of the larvae with a microscope that had ultraviolet light and illuminated the stage of the apparatus. The bags then turned bright blue.

These larvae use a mechanism that regulates their buoyancy by means of two pairs of internal air-filled sacs.

The blue fluorescence was due to resilina, an elastomeric protein found in some parts of insects where the elasticity it’s key. It is what drives, for example, the incredible jump of a flea. But “the strange thing about resilin is that it is not really elastic. It swells if you make it alkaline and contracts if you make it acidic”, explains the scientist.

Together with the doctoral student Evan McKenzie, who conducted the experiments, Matthews discovered that the insect it does not secrete gas into its air sacs to expand them. Instead, it changes the pH level of the bag wall, causing resilin bands within the air sac wall to swell or contract in response. And so the volume of the bags is adjusted.

These actually function as mechanochemical engines, converting potential chemical energy changes into mechanical work. “This is a really strange adaptation that we were not looking for,” says the zoologist. “We were just trying to figure out how they can float in the water without sinking!” he exclaims.

Fountain: SINC

Rights: Creative Commons.

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