How the fan worm got its tentacle-eyes

The strange compound eyes of the tiny fan worm may shed light on the evolution of vision

The tiny compound eye of the fan worm has a diameter of only 250 microns.
The tiny compound eye of the fan worm has a diameter of only 250 microns.
Michael Bok

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

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

By studying the genome of a Megalomma interrupta fan worm taken from the Great Barrier Reef, the researchers identified a number of genes that produce light-sensitive cellular signalling components such as opsins and g-proteins in the fan worm’s eyes. These collections of genes had previously only been seen in simpler photoreceptors in the brains of some invertebrates.

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

Curated content from the editorial staff at Cosmos Magazine.
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