How The Fly Flies

Max Planck scientists discover gene switch responsible for flight muscle formation
Flies are real flight artists, although they only have small wings compared to their body size. Scientists at the Max Planck Institute of Biochemistry in Martinsried near Munich, Germany, recently identified the genetic switch that regulates the formation of flight muscles. “The gene spalt is essential for the generation of the ultrafast super muscles,” emphasizes Frank Schnorrer, head of the research group “Muscle Dynamics”. “Without spalt, the fly builds only normal leg muscles instead of flight muscles.” The scientists’ results have now been published in Nature.

In order to fly efficiently, flies have to flap their small wings very fast. This causes the familiar buzzing and humming of the small beasts. The fruit fly Drosophila melanogaster moves her wings at a frequency of 200 hertz – that means its flight muscles contract and relax 200 times per second. “In contrast, a hundred meters sprinter who moves his legs only a few times per second moves like a snail,” Frank Schnorrer describes. How can the fruit fly flap its wings at such a high frequency?

Muscles control all body movements, including the wing oscillations. However, flight muscles are unique. Their contractions are not only regulated by nerve impulses as usual, but additionally triggered by tension. Every fly has two categories of flight muscles which enable the wing oscillations: One type moves the wings down and, at the same time, stretches the other type which induces its contraction. Such, the wings are pulled up again and stable wing oscillations begin.

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First superfast muscles in mammals help bats catch prey

Bats are able to locate their prey using echolocation produced by a special kind of "superfast" muscle, scientists have found.

These specially adapted muscles can contract 100 times quicker than most of the muscles in human bodies.

This is the first time such muscles have been seen in mammals, although they had previously been found in rattlesnakes, some fish and birds.

The Danish findings are published in the journal Science.
Bats use echolocation to navigate in total darkness, as well as to catch flying insects in mid air.

In order to pinpoint the insects with enough accuracy and speed to catch them before they fly away, the bats need to make a lot of calls in rapid succession.

As the bat approaches its prey target, the frequency of calls increases up to about 190 calls per second, creating what is known as the "terminal buzz".

Researchers at the University of Southern Denmark, led by Prof Coen Elemans, designed tests to investigate just how fast the terminal buzz could be.

They discovered that the maximum frequency of the buzz was not limited by the echo return time, but was controlled by the muscles in a bat's throat.

These muscles contracted once to produce each call, totalling nearly 200 contractions, or one every five milliseconds.

Such rapid contractions made these "superfast muscles", a type of muscle which has previously only been seen in the sound-making organs of rattlesnakes, the humming Oyster Toadfish, and many songbirds.

They had not been identified in mammals, but Prof Elemans said: "I had a hunch, that if they were in mammals, they would be in bats".

Fast but weak
The superfast muscles seen in these bats can contract 100 times faster than most muscles in the human body, and 20 times quicker than the fastest muscles we have - those that control the movement of our eyes.

Muscles that can contract so quickly need cells that have special adaptations.

The extra energy needed to power the cells comes from a much higher density of mitochondria - the energy producing machines within the cell. Compared with a "normal" cell, the superfast muscle cells have 30% more of these mitochondria.

By Leila Battison Science reporter
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