Fangblenny changes colour to mimic prey

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Australian scientists have proven that the Bluestriped fangblenny, an aggressive mimic of the juvenile Cleaner wrasse is able to adopt mimic colours depending on the availability of cleaner fish.

The study by Karen Cheney, Alexandra Grutter and Justin Marshall is published in the latest issue of the journal Proceedings of the Royal Society B: Biological Sciences.

The Bluestriped fangblenny (Plagiotremus rhinorhynchos) is an aggressive mimic of the Cleaner wrasse (Labroides dimidiatus) that instead of cleaning reef fish by removing ectoparasites and mucus from larger client fish, attacks them in removing and eating scales and dermal tissue.

The fangblenny has recently been shown to be a facultative mimic (ie it is able to switch between mimic and non-mimic colours at will), but the cues for doing so remain poorly understood.

In this study, the authors set out to study three things: (1) whether the presence of cleaner fish served as a visual cue for colour change in the fangbleny; (2) whether the proportion of mimetic to non-mimetic fangblenies in a given area was dependent on the number of juvenile cleaner fish in the area and (3) using objective colour analyses to determine if the fangblenny is an accurate mimic of the cleaner fish and whether non-mimic fangblennies closely matched the colours of other fishes they associated with (non-mimic fangblennies often hide in similarly coloured shoals of fish).

The authors found that the presence of cleaner fish indeed served as visual cues for the assumption of mimic colours in the fangblenny, with the change occurring within 30 minutes under experimental conditions.

This result was supported by field observations that the proportion of mimic to non-mimic fangblennies was positively correlated to the number of juvenile cleaner fish in the surrounding area.

Lastly, the colour analyses (using spectrophotometry) showed the fangblennies to be both accurate mimics of the cleaner fish, as well as being able to appear reasonably similar to other shoaling fishes the non-mimetic fangblennies associated with.

The authors write: Facultative mimicry is a unique strategy that is uncommon in the animal kingdom and allows mimics to resemble a number of different species.

This enables individuals to persist in a variety of environmental conditions; for example, such a strategy would be useful to fangblennies on reefs where cleaner fish juveniles are not present, or are present in low numbers.

The ability to adopt colour forms different to that of its main model provides the mimic with added strategies for avoiding detection by potential victims of attack, or by potential predators.

For more information, see the paper: Cheney, KL, AS Grutter and NJ Marshall (2008) Facultative mimicry: cues for a colour change and colour accuracy in a coral reef fish. Proceedings of the Royal Society B: Biological Sciences 275, pp. 117"122.