By EBEN HARRELL Thursday, Jan. 07, 2010
Scientists often warn against anthropomorphism — the attribution of human characteristics to animals or even nonliving things. But it's hard to resist the charm of Labroides dimidiatus, a species of fish otherwise known as the bluestreak cleaner wrasse. These colorful little critters make their living in coral reefs by setting up cleaning stations where larger fish — often predators that might otherwise gobble them up — can stop by to have their skin cleaned. The wrasse busy themselves like car wash attendants fussing around a sports car, nibbling off parasites, dead tissue and other blemishes, and nourishing themselves in the process.
(See the top 10 animal stories of 2009.)
Since the discovery of the fish's behavior in the 1950s, cleaner wrasse have provided biologists with a delightful example of cooperation in nature. But now an international team of scientists have observed another unusual trait in the fish, and one that may shed light on higher social animals, including humans. The wrasse, it appears, know how to punish each other.
It turns out that — surprise! — cleaner wrasse don't actually like to munch on dead flesh and parasites. They much prefer the slimy mucus that coats healthy fish skin, which is rich in carbohydrates. So in nature, the wrasse occasionally cheat and take a nip of their client's body. When they work alone, the wrasse strike a balance between cleaning and cheating so as not to lose their clients' business. But wrasse also work in pairs. In these situations, explains Redouan Bshary of the Universite de Neuchatel in Switzerland, one of the authors of a new study in the journal Science, the fish face a dilemma: "Theoretically, the best idea would be to bite your client right away before your partner does, because if the client swims away, you get the benefits of the tasty bite but the costs are shared." But the fish tend to behave themselves.
It's punishment — or just the threat of punishment — that's the key. Bshary and others already knew that in the wild, male wrasse, which are larger than females, become hopping mad when their partners steal a bite of their clients, chasing the female around in a threatening manner. To prove that this was indeed the physical scolding it appeared to be, Bshary and colleagues ran a tank experiment in which they introduced a plate full of normal fish flakes (which wrasse like) and prawns (which wrasse love) to two fish. If either fish ate a tasty prawn, the researchers removed all the food from the tank. Sure enough, when the female nibbled the prawns, the male wrasse went berserk. As the experiment progressed, the females became less likely to eat prawns (the males still ate the prawns with impunity).
Read more:
http://www.time.com/time/health/article/0,8599,1952458,00.html#ixzz0c9hymrjy
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