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How urchins see when they have no eyes

By Colin Ricketts - 01 Jul 2011 15:25:1 GMT
How urchins see when they have no eyes

It sounds like the set-up to a joke: how does an animal with no eyes see? Researchers from Sweden trying to answer that question have found that the answer when it comes to sea urchins is that they use their whole body.

Eyes in the animal kingdom are incredibly varied. Some creatures are blind, others have incredibly complex eyes giving them vision they can rely on to stay safe - as anyone who's failed to swat a fly will know.

The eye is often so complex that since the days of Charles Darwin evolutionary biologists have marvelled at how such a structure could have evolved and it's even been used as an argument in favour of so-called Intelligent Design, the biblical theory of creation and evolution.

Despite having no eyes, however, a sea urchin is able to react to light. How?

Researchers already knew that these sea creatures had large numbers of genes which were familiar from our own retina - the light sensitive part of the human eye - and produce a protein that is found in many animal eyes, called opsin.


So, while they have no eye as such, the urchins have many many light receptors, found on the end of the feet that cover their entire body.



Top Image: Red Sea Urchin (Strongylocentrotus franciscanus) Credit: © naturediver