 Clown Fish About To Be Sold
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July 11, 2003 — Children who rush out to buy a clownfish, the cute little star of the new Disney cartoon "Finding Nemo," may be getting something that their parents may not have bargained for: a piscatorial transexual.
Animal behaviorist Peter Buston of New York's Cornell University studied groups of clownfish (Amphiprion percula) in tanks.
Each group of clownfish, he discovered, comprises a breeding pair and up to four non-breeders.
At the top of the social hierarchy is the largest fish, a female breeder; she is followed by the second largest fish, a breeding male.
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After them, progressively smaller in size as they decrease in rank, come the non-breeders.
Buston found that if he removed the top-ranking female, the breeding male changed sex and increased in size to become the female breeder.
That caused a knock-on effect throughout the group. The largest non-breeder became the breeding male, and all the other non-breeders increased in size as they moved up a social notch.
Clownfish — an aquarium-lover's delight because of their orange "face" and white rings — make the astonishing switch in sex and size in order to ensure harmony within their group, Buston suggested.
"This strategy to prevent conflict is a surprising departure from the more usual ploy used by many animals, of modifying their behavior within the group," he reported in Thursday's issue of Nature, the British science weekly.
"The maintenance of size differences may resolve evolutionary conflict over group membership, because subordinates do not become a threat to their dominants," he wrote.
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