Scientists' understanding of animal sight has taken a turn toward the bizarre
E.M. Ullrich-Lüter Et Al/Integr. Comp. Biol. 2013
It sounds like a riddling trick: How can an animal with no eyes still see? But it’s a serious scientific question — the trickiest kind of riddle.
Sea urchins don’t have anything that people recognize as an eye, says Sönke Johnsen of Duke University. Urchin bodies are mobile pincushions in purples and pinks to browns and blacks, bristling with a mix of spiky spines and soft, stretchy tube feet.
Yet at times urchins act as if they “see” large-enough somethings in their world, even if the how and what of their visual systems have been hard to pin down. “Maddening,” Johnsen says. “They almost always have what looks like purposeful behavior, but you can’t quite put your finger on it because there’s something so alien about them.”