Mimicry - Original or Copy?

The pressure of evolution in a coral reef leads to many different strategies of survival. One is to become toxic to predators. That doesn't help the species if the predator doesn't know and eat it anyway. In this case the predator will also die, which is obviously a disadvantage for both the predator and the prey. Only by evolution - natural selection - the predators will learn to avoid toxic prey.

This is exactly what the Mimic Leatherjacket, also called blacksaddle filefish (Paraluteres prionurus), is using to its advantage. As a filefish it is non-toxic and thus an easy prey. However, it looks almost identical to the highly toxic black-saddled toby (or Valentin's sharpnose puffer, Canthigaster valentini) and is even schooling with the puffer (although generally it forms only a small fraction of 5% of the schools).

This is a nice example of visual mimicry. The pictures below show the two species. One has to look carefully to see the differences (click on both pictures to enlarge both simultaneously). The filefish (on the left side) is hiding its file-like first dorsal fin which the puffer (picture on the right side) is missing. The coloration of the eyes is quite different and also the texture of the body shows some differences.