A typical starfish has five-sided symmetry. With no clear head, the starfish can move in any direction, led by any one of its five arms. If you were feeling particularly cruel, you could fold one up in five different ways, so each half fitted exactly on top of the other. We humans, like many other animals, have only two-sided symmetry. We’re ‘bilateral’ – our right half mirrors our left, and we have an obvious head.
These two body plans might look radically different, but looks can be deceiving. Chengcheng Ji and Liang Wu from the China Agricultural University have found that starfish have hidden bilateral tendencies, which reveal themselves under times of stress.
Starfish belong to a group of animals called echinoderms, which also include sea urchins, sea cucumbers, brittlestars. As adults, most of the group have five-sided symmetry. As larvae, they’re very different. A baby starfish looks entirely unlike ...
