Organismal biology: Sea urchins 'see' with their feet

Journal name:
Nature
Volume:
473,
Pages:
126–127
Date published:
DOI:
doi:10.1038/473126e
Published online

Sea urchins can respond to light despite having no obvious eye structure. Researchers have now pinpointed a possible mechanism for this, involving light-sensitive cells in the creatures' numerous tube feet.

M. I. ARNONE

Maria Arnone at the Anton Dohrn Zoological Station in Naples, Italy, and her colleagues show that the feet of Strongylocentrotus purpuratus (pictured) contain a type of photoreceptor cell found in many other animals, including vertebrates. The researchers found that two key photoreceptor genes (pictured in dark purple and red) are expressed in the feet.

The photoreceptor cells connect to the animals' nervous system (green). The authors suggest that the entire sea urchin can function as a large compound eye, and that the shadow cast by the animal's opaque skeleton on some of the light-sensing cells may enable directional vision.

Proc. Natl Acad. Sci. USA doi:10.1073/pnas.1018495108 (2011)

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