The eyes have it

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

Cosmos - - Digest -

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.

CREDIT: MICHAEL BOK The tiny com­pound eye of the fan worm has a di­am­e­ter of only 250 mi­crons.

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