To be or not to be a mimic

What is the world coming to? An unsuspecting reef fish steps up to have its parasites removed by its favourite cleaner fish, the bluestreak cleaner wrasse, but instead of a thorough going over, it gets a nasty nip from the cleverly disguised bluestriped fangblenny, intent on a quick feed.

Mimics in nature have usually evolved to resemble foul-tasting animals, in a bid to protect themselves from predators, but the bluestriped fangblenny fish mimics a model -the bluestreak cleaner wrasse- that is not only harmless but actually beneficial to many reef fish species.

Researchers at University of East Anglia, Isabelle Côté and Karen Cheney, have discovered that fangblennies can choose when to be mimics. When no cleanerfish are nearby, fangblennies can turn off their remarkable black-and-blue cleaner-like colours. They become brown, green or orange, add a second side stripe to their bodies, and melt into large shoals from which they attack unsuspecting fish swimming by.

Opportunistic mimicry allows fangblennies to live on all reefs, even those where there are no cleanerfish. It seems that natural selection can result not only in extraordinary resemblances between unrelated animals, but also in an astonishing flexibility in when to show off these similarities.

’It was already known that these fish could be found in various colour forms. But it was very exciting to find that individuals can change colour. Mimicry is fairly common in this family so I’m keen to see whether the same phenomenon is found in related species.’ said Isabelle Côté.