Video: How roaches see in pitch-black

Ever wonder how cockroaches scurry around in the dark while you fumble to switch on the kitchen light? Scientists know the insect navigates with its senses of touch and smell, but now they have found a new piece to the puzzle: A roach can also see its environment in pitch darkness, by pooling visual signals from thousands of light-sensitive cells in each of its compound eyes, known as photoreceptors. To test the sensitivity of roach vision, researchers created a virtual reality system for the bugs, knowing that when the environment around a roach rotates, the insect spins in the same direction to stabilize its vision. First, they placed the roach on a trackball, where it couldn’t navigate with its mouthpart or antennae. Then the scientists spun black and white gratings around the insect, illuminated by light at intensities ranging from a brightly lit room to a moonless night. The roach responded to its rotating environment in light as dim as 0.005 lux, when each of its photoreceptors was picking up only one photon every 10 seconds, the researchers report online today in The Journal of Experimental Biology. They suggest that the cockroach must rely on unknown neural processing in the deep ganglia, an area in the base of the brain involved in coordinating movements, to process such complex visual information. Understanding this mechanism could help scientists design better imaging systems for night vision.

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