Photoreception

Unfocused eyes in the stars

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Science  09 Feb 2018:
Vol. 359, Issue 6376, pp. 649-650
DOI: 10.1126/science.359.6376.649-c

Brittle stars detect light with a network of opsincontaining cells.

PHOTO: SARAH DAVIES

Imagine having a whole-body-surface visual system. The brittle star Ophiocoma wendtii and its relatives are decorated with a surface layer of calcite hemispheres. Although these have been implicated in light focusing, there has been little anatomical evidence of an underlying photoreceptor network. Sumner-Rooney et al. found a comprehensive network connecting opsin-containing cells across the entire body surface of the stars. However, these cells project past the calcite structures, which apparently are not acting as microlenses, as previously thought. The projecting photoreceptors are thus not eyes in the sense of image-forming vision. Rather, the opsin-containing cells detect high-contrast light changes, evidently to coordinate shade-seeking, predator avoidance, and color-changing reflexes.

Proc. R. Soc. B 285, 20172590 (2018).

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