RSS There?s something fishy with some of the Clown Tangs of the Seychelles

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  1. MASA Admin

    MASA Admin Moderator

    8 May 2007
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    Part of the excitement about being a fancier of marine life is the ability to follow leads of curiosity, no matter how improbable the odds of success in finding something meaningful, even when you don’t really know what you are looking for. Recently we stumbled upon one grainy picture of an exceptional clown tang from the Seychelles which led us on a photo hunt that yielded more than a handful of interesting fish.

    [​IMG]The first clown tang from the seychelles we spotted with abnormal striping which led us on this meta-search. Photo by FlickR user Adrien

    It’s hard to explain how one picture with location data can appear so promising and stimulate our sleuthing instincts, but more often than not our ‘spidey sense’ can turn us on to something interesting. The image above was that first clue to a puzzle that we haven’t yet pieced together, but we believe there’s something in the population of Acanthurus lineatus from the Seychelles warranting further investigation.

    [​IMG]A normal Indo-Pacific Acnthurus lineatus from the Indo Pacific showing very straight and uniform blue and black striping. Photo by Paul Asman & Jill Lenoble

    A ‘normal’ clown tang should have fairly straight body stripes which curve gently around the flanks and the even blue lines are bordered by an even black trim. Above you can see a typical clown tang with the cooky-cutter pattern which is widespread from the Western Indian Ocean to the central Pacific Ocean. Maybe it’s because we really love this particular species, and have examined hundreds of specimens over the years, but the stripes of the specimen pictured below show just the slightest deviation from the normal pattern.

    [​IMG]Relatively normal clown tang with very slightly abnormal stripes. Photo Sey Praslin

    [​IMG]This clown tang is showing a moderate degree of waviness to some of its stripes on the flanks. Photo Philippe Vidal

    In the good and clear side-profile pictures of some specimens of clown tangs in the Seychelles, the squigglyness of the side stripes becomes more apparent. Again on its own this abnormality is hardly anything to mention, let alone write about, but further meta-searching led us to find even more oddball A. lineatus with ever more extreme aberrations.

    [​IMG]In this image showing two Acanthurus lineatus you can see the squigglyness of the lines on the flanks is visible in both specimens. Photographer unknown

    [​IMG]The presence of branching lines is sometimes seen in clown tangs all throughout its range but it appears to be slightly more common in the Seychelles. Photo by FlickR user Antonka

    [​IMG]The very slight aberration to the stripes we observed in Seychelles clown tangs is exaggerated almost to a squiggle in this specimen. Photo by FlickR user Photosmr

    [​IMG]Once we found a few more specimens with the squiggle-lines on theirs sides we grew in confidence that we were on to something. Photo by FlickR user Antonka

    Once again, if we saw one of these clown tangs at the local fish store or in the wild, a single specimen with abnormal stripes and patterns is not enough to raise any flags. Aberrations of color and pattern happen in practically all reef fish that we know about and it’s relative what is considered ‘normal’ for a species. However in the Seychelles the aberrations seemed to be piling up and more common than regularly striped clown tangs.

    It’s a curious thing to be investigating a hunch about marine fish through piles of online photographs, and even curiouser to actually stumble across what you seek, even when you don’t know what it is you were looking for. So you can imagine how stunned we were when we actually uncovered an extreme example of the aberrant clown tangs which is a ‘smoking gun’ for something that we can’t explain.

    [​IMG]The irregular striping is quite pronounced in this Seychelles clown tang. Photo by FlickR user Antonka

    There are plenty of clown tangs in the Seychelles which show relatively normal color and pattern but there are enough unusual ones for us to postulate that some phenomenon is affecting their appearance. With very little data to go on, our first and only hypothesis about these unusually patterned clown tangs is that there may be some degree of localized inbreeding in this region, similar to the Koi Queen Angelfish of St. Paul’s Rock.

    In this island off of Brazil the Holacanthus ciliaris specimens express very unusual colors and patterns, and even odd finnage due to well-documented inbreeding in this isolated rock in the Atlantic ocean. The Seychelles are moderately isolated from other west indian ocean islands but it still constitutes a large enough area that the resident population is relatively large. Genetic analysis alone can confirm or refute that genetics are even involved in the odd appearance of these clown tangs but if you ever end up diving or snorkeling in the Syechelles, do be on the lookout for some oddball Acanthurus lineatus. 

    [​IMG]This is the “super freak” clwon tang we hoped we’d find in the population of Seychelles Clown tangs but we never could have imagined we’d actually find a picture of such a unique fish. Photo by Hugues Brun

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