Cockroaches Accumulate Light to See in the Dark
Cockroaches could inspire superheroes if they weren't so repulsive. Some species can hold their breath for as long as 40 minutes. Others can survive blasts of strong radiation, subsist on paper and dried glue, or live for weeks without a head. Recently researchers discovered another superpower: the nocturnal creatures can see in near–pitch black by pooling light signals over time, like time-lapse photography.
Physicists at the University of Oulu in Finland—where it is too cold for roaches to live outside of the laboratory—put about 30 American cockroaches through virtual-reality experiments to test their night vision. No, they did not make them wear tiny goggles. Instead they put each roach on a tracking ball surrounded by a spherical screen. Under increasingly dark conditions, the researchers projected images of black-and-white moving stripes onto the screen, triggering a reflex that made the roaches walk toward the stripes.
The scientists also harmlessly inserted a recording microelectrode into one of the roaches' nearly 360-degree compound eyes to record the electric blips triggered in the photoreceptor cells by photons, or particles of light. In conditions equivalent to a moonless night, the roach eye absorbed one photon every 10 seconds.
Usually such conditions are too dim for vision. “That's an amazingly small amount of photons,” says Matti Weckström, a biophysicist who carried out the experiments. But the roaches could see just fine. Taking into account the size of the experiment's stripes, the optical properties of the roaches' eyes and the amount of photons available, the team concluded that the roach nervous system pools information from its thousands of photoreceptors over time—in effect, accumulating electrical neural signals and using the summation of those signals to see. The team reported its findings last December in the Journal of Experimental Biology.
http://www.scientificamerican.com/article/cockroaches-accumulate-light-to-see-in-the-dark/
