June 3, 2009

Squids use symbiosis to detect light

U.S. scientists have determined certain squids can detect light through a symbiotic organ, not just through their eyes.

University of Wisconsin-Madison researchers said the light-emitting organ some squids use in camouflaging themselves to avoid being seen by predators also detects light. That, the scientists said, is a finding that might lead to insights into the mechanisms of controlling and perceiving light.

Professor Margaret McFall-Ngai, who led the study, said the light organ, which comes from different tissues than the eye during development, uses the same proteins as the eye to see light. She said that organ is a natural model of symbiosis -- an interdependent relationship between two different species in which each benefits from the other.

In the case of E. scolopes squids, she said the light organ is filled with luminous bacteria that emit and detect light, providing the squid protection against predators. In turn, the squid provides housing and nourishment for the bacteria.

The study appears in the Proceedings of the National Academy of Sciences.