Squid turn skin into living jewels

Lots of animals have sparkly skin, but squid are one of few that can change the colour of their shimmer.

Now Trevor Wardill and colleagues at the Marine Biology Laboratory in Woods Hole, Massachusetts, are getting new insight into how they do it by zapping their skin with electricity.

In this video, iridescent patches of skin change hue when nerves near the fin are stimulated. The signal travels through a network of nerves in the skin, allowing the squid to cycle through a range of hues from blue to red in about 15 seconds.

They also change colour via a similar mechanism that alters pigment-containing cells, but the animals are able to display different opaque hues much faster.

The experiment shows that rather than being a local reflex, the central nervous system controls changes in shimmer. But how squid pick and maintain their skin colour is still a mystery.

The hue of the shimmer helps the animals camouflage themselves - but they are colour blind, so scientists are puzzled by how they know they've got it right.