Fly Eyes Prevent Blurry Vision

There's no gold medal in sight, but at least one species of fly manages to avoid obscured vision during flight by borrowing a page from Olympic ice skaters. The solution, scientists report in tomorrow's issue of Nature, involves independent movement of the head and thorax in a way similar to how skaters avoid dizziness by snapping their head before their body completes its rotation. The results should help researchers piece together how the eyes of insects process images.

In determining how Calliphora vicina--blowflies--manage to stabilize their gaze during banked turns, researchers have struggled to determine whether the insect's head and thorax move independently or in tandem. To measure the fly movements with precision, neuroscientist Kees Schilstra and his colleagues at the University of Groningen in the Netherlands constructed miniature sensors, which they mounted on the head and thorax of four flies before setting the insects loose in a cage.

Collecting data during 12 minutes of flight, the researchers recorded nearly 7000 body turns for the flies. By comparing the speed of the head and the thorax throughout the flight, they found that during each turn the head shifts after the body starts rotating and stops before it levels out. Measurements taken by the sensors will allow researchers to reconstruct the information gathered by fly eyes, says author Hans van Hateren.

Experts are impressed by the data, which they say will lead to a better understanding of visual information processing. "In almost free flight, gaze stabilization really works," says Martin Egelhaaf of the University of Bielefeld in Germany. Egelhaaf adds that he will be using the new sensor system to study visual information processing in the nervous system of flies.

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