Their whole body surface is are their eyes, as we hear in “Sea Urchins See With Their Whole Body” (ScienceDaily, September 12, 2011):
he research group behind the study showed that the photoreceptors seem to be located on the tip and base of the tube feet that are found all over the sea urchin’s body and are used to move.
“We argue that the entire adult sea urchin can act as a huge compound eye, and that the shadow that is cast by the animal’s opaque skeleton over the light-sensitive cells can give it directional vision,” says Dupont.
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