It appears sea urchins might just use their entire body as one huge eye. Previous research has shown certain marine invertebrates react to light even without apparent “eyes” leaving scientists to wonder how did they see but new research suggests sea urchins may have light-sensitive cells throughout their feet behaving much like one giant eye.
Genetic analysis of the California purple sea urchin had already yielding data showing a large amount of their genes were linked with what is found in the development of retinas — the light-sensitive tissue in the inner eyeballs of humans and other invertebrates. And other research has suggested urchins might have a spattering of light-receptor cells all over its body that collectively act much like a retina.
But recent research has found that there are two distinct groups of light receptor cells are found concentrated at the base and tips of the urchins’ feet. Considering there are over 1,400 feet on the California purple urchin, the research team speculate urchins use these multitude of tube feet as retinas and the rest of their bodies to shield against the extra incoming light allowing them to have some form of “vision.”
Since previous work discovered the number and placement of spines on a sea urchin can affect how sharp its vision might be, the new data definitely helps support the theory that the entire body of sea urchins just may in fact act as one massive eyeball.
The sea urchin-eye study appeared May 2 in the journal Proceedings of the National Academy of Sciences.