Scientists have found only one other animal that can regulate its buoyancy in the water using swim bladders, and it is probably not what you were expecting.
The phantom midge is a type of lake fly, but before it can take to the air, it must first grow up in the water. Since 1911, we have known that these glass worms have gas-filled sacs on either end of their body.
We didn't know how the insects controlled those strange organs. The answer has been accidentally revealed by a trick of the light.
A group of animals were swimming in a rain-filled cattle tank.
Matthews recalls that the insects were floating neutrally in the water.
Chaoborus andlarvae are the only insects that are close to being neutrally buoyant.
Unlike a fish, oxygen gas cannot be transported into the air-sacs of a phantom midge because insects don't have enclosed circulatory systems with oxygen-transporting red blood cells.
How do their organs inflate and deflate?
The air sacs are shown by the aquatic chyborus nymph. Philip Matthews.
Matthews took some of the larvae back to the lab and put them under a microscope. The air-sacs started to glow a bright blue when he turned on the ultraviolet light.
The color of the sacs suggested they were made of aprotein known as resilin, which has elastic, rubber-like qualities.
Evan was the lead author of the new study and began experimenting with the air sacs in the lab, deflating them with acidic or alkaline exposure.
Air could be pushed in and out of the sacs.
Air sacs were removed from the phantom flies. Philip Matthews.
This is a really bizarre adaptation that we didn't go looking for.
We were trying to figure out how they can float in water.
They found phantom midges could sink, rise, or float by manipulating their air-sac walls. Without the need for blood to inflate or deflate the organs, gas can be diffuse in and out.
The authors say that the whole process works like a Mechanochemical engine.
The motor is very easy to use, and it can travel very deep into the water, making it an ideal vehicle for phantom midges.
One species of phantom midge has been found more than 200 meters down in a low oxygen environment in East Africa.
The new research suggests that the larvae don't have to swim to get there, they just have to sink.
Current Biology published the study.
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