Anonim

Let's get a chela … and the neighbor's grass is more beautiful
The fiddler crab defends the territory, but not only his … The results of an Australian study.

The fiddler crab helps the neighbor when he is threatened by a stranger: altruism or strategic choice? © Chris Lukhaup
The fiddler crab helps the neighbor when he is threatened by a stranger: altruism or strategic choice?
© Chris Lukhaup

"This is my house: away or … I call the neighbor!": It seems to cite the fiddler crab (Uca mjoebergi) with the huge claw raised against the approaching intruder. It is not the highlight of a fairy tale for children: it is what happens, a separate talking crab, if an invader tries to enter the den of this crustacean, called violinist because of the presence in the male of a chela much larger than the other . The neighbor in these cases runs to the aid of the unfortunate.
If you give a chela to me … To discover this mechanism were the researchers of the National University of Canberra (Australia), who observed how a landlord, guarding his den and threatened by another crab, can count on neighbor's help. However, the researchers explain that this is not altruism, because the ally is always bigger than the owner of the den in danger, but of a form of mutualism. It is better to keep a neighbor who is stable and not belligerent and fight on his side, than to have to accept a new neighbor that could instead be a threat.
The infallible weapon for these invertebrates is the highly developed chela, often disproportionate to the rest of the body and conspicuously colored, with a dual function: used to impress females, it is useful for launching attacks against invaders.
Instructions for use at the neighbor's home. However, these crabs are not the only ones to benefit from the help of neighbors. In fact, several studies have shown that many animals derive suggestions for their conduct and survival from a kind of public knowledge.
Where can you find the best food? What are the characteristics of the ideal partner? Where to look for it? No guide is given to the young animal that faces life: the only strategy is to look around and imitate the behavior of others.
Among the many studies cited by a recent article published in the journal Science, which would demonstrate the use of a public and shared knowledge heritage, there is the one concerning the tiny guppy fish (Poecilia reticolata). Females of this species can change sexual tastes only by looking at other females and letting themselves be influenced by these: if they first liked a light-colored partner, after spying on the mates of others with darker subjects, the preference went to the male in dark gray.
(News updated July 28, 2004)