Abstract

Echinoderms in general, and especially the brittlestars (Ophiuroidea) exhibit a wide range of responses to light intensity, from a largely light-indifferent behavior to pronounced color-change and rapid escape behavior. The latter reaction is particularly unexpected in these animals since it is usually associated with the presence of discrete photosensory organs. No specialized eyes have, however, been documented in brittlestars and their reactions to light have been linked to “diffuse” dermal receptors. Here we show that certain single calcite crystals used by brittlestars for skeletal construction are also a component of discrete photosensory organs, conceivably with a compound-eye function.

© 2002 Optical Society of America