The eyes have it

Vision evolves in some funny places. On tentacles, for instance.

Fan worms live in tiny tubes on the sea floor and extend feathery tentacles upwards to sift through the water for food particles. The tentacles have tiny compound eyes that act like shadow or motion detectors and alert the worm to danger, enabling it to quickly shrink into to the safety of its tube.

The eyes evolved separately from the visual systems of related creatures, specifically to meet the needs of the fan worm’s lifestyle, according to research from a team of Swedish scientists led by Michael Bok at Lund University and published in the journal Current Biology.

By studying the genome of a Megalommma interrupta fan worm taken from the Great Barrier Reef, the researchers identified a number of genes that produce the light-sensitive cellular signalling components present in the animal’s eyes. The eye structure is more closely related to those found in vertebrates than in insects.

“These eyes could offer many clues about the emergence of new sensory systems and how the first eyes may have arisen,” Bok says.