Sydney  - Without their distinctive livery, lots of little reef fish would look much the same. Colour differentiates them, not shape.

The blue-striped fangblenny, found in coral reefs in Indonesia and Australia, is different. What marks it out from every other fish known to man is that it can change colour at will.

The default colour is brown, but the fangblenny can switch to yellow or a range of other bright hues to deceive other fish.

"Their repertoire of disguises appears to prevent or reduce detection by potential victims," says Queensland University marine biologist Karen Cheney. "They may also escape from predators by hiding in a large shoal."

Cheney's work, published in The Proceedings of the Royal Society, is important because the fangblenny is one of a kind in the fish world. Lizards use the same technique to hunt or hide, but the fangblenny is the only fish so far found to have that ability.

Without the skills of a chameleon, the fangblenny would be hard pressed to live as it does. It nibbles the dead scales of larger reef fish - a diet made possible by deceiving other fish into thinking that's not what it's about.

A particularly clever trick is morphing into the colours of a juvenile cleaner wrasse. The wrasse lives a charmed life. It helps larger fish avoid potentially deadly infestations by nipping off the parasites that cling to them. In return for this service, it is left alone by much bigger fish. (dpa)