Aberration reversion of Ctenochaetus documented by Cairns Marine
We’re not unfamiliar to the sight of “xanthic-koi” type aberrants that plague various fishes. Vitiligo and other forms of patchy off-coloured specimens appear from time to time, and seem to be particularly prevalent in surgeonfish of the genus Ctenochaetus as well as Centropyge. Although we still have no clue what causes this to occur, we know for a fact that this coloration is fluid and mosaics about the body as time goes by. Most of the time the fish loses the koi-colours either completely or partially and revert to wild type coloration, or keeps the aberration but in an ever changing manner.
In most examples, the fish arrive from the wild with partial xanthic coloration or an aberrant koi pattern, and then proceeds to lose it quickly after a few weeks. Few specimens have managed to hold this coloration. Various theories have been put forward by hobbyists, saying that these could be sexual displays in the wild. Others have hypothesised that viruses and other infections have led to the appearance of such mutations.
In rare instances, healthy fish with wild type coloration can develop this phenomenon in captivity. Matt Wandell of Steinhart Aquarium has documented the development of such coloration in previously normal looking fish. The phenomenon appears to be transmittable, although none of the fish showed any adverse health effects.
An excerpt on skin pathology in wild Ctenochaetus from the journal of fish diseases.
In a paper on skin pathology in wild Ctenochaetus from the journal of fish diseases, similar discoloured examples we know and refer to as “aberrants” were discussed. The paper reveals the discolouration to be a result of chromatophoromas, iridophoromas and other forms of cancer. It at least provides some answers to patchy coloration in certain reef fish, but it does not shed light on why and how these fish revert back to their wild type coloration in captivity, assuming those are sufferers of the same affliction in the first place. If they are, are they able to recover quickly once removed from the causative agent? Or are those “xanthic” and “piebald” aberrants showing up with a totally different problem altogether?
The specimens in the paper range from having discoloured skin to bleeding ulcers as a result of cancer. None of the aquarium aberrants were documented to show any form of ulceration, apart from the abnormal coloration. This could be a totally different thing altogether.
Rob Lanceley of Cairns Marine has kindly shared with us a series of photos depicting the colour change of an aberrant koi type Ctenochaetus. We know that they are able to lose the yellow, but the process is very seldom recorded.
The gallery below shows a series of photos taken at the Cairns Marine facility of the same fish. It’s quite clear that the fish is losing some of the yellow and slowly regaining its wild type coloration. Again, it’s still pretty unclear what causes this in the first place, and why it is able to go away so quickly in captivity.
Kai is a systematic ichthyologist at The Australian Museum, Sydney. His research interests combine the use of cutting-edge next generation sequencing techniques with traditional methods of morphology to better understand the evolutionary history of coral reef fishes. He is a legacy ReefBuilders contributor, having previously written close to give hundred articles under his pseudonym LemonTYK.
