FISH may not drive fast cars, but they do seem to have ways to show off their sexual prowess. Male cichlids (Cyathopharynx furcifer) in Lake Tanganyika, Zambia, signal their place in the pecking order by building mating craters.
Males spend hours building and tending their craters, which appear to serve no purpose other than to provide a place to mate. They vary in diameter from 20 to 50 centimetres, with the larger ones generally belonging to larger, healthier fish.
Franziska Sch盲delin and Michael Taborsky from the University of Berne in Switzerland reduced the size of some craters and enlarged others. 鈥淢ales that got a smaller crater started to rebuild immediately,鈥� Sch盲delin says, while those that ended up with a larger crater set about knocking it back to its original size (Animal Behaviour, vol 72, p 753).
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鈥淓very male always builds a crater the same size,鈥� Sch盲delin says. She speculates that they are unwilling to trade up to a bigger crater, perhaps because females will leave if they discover the owner isn鈥檛 up to scratch or because other males will attack them. Sch盲delin and Taborsky suggest that crater building may be an 鈥渆xtended phenotype鈥�: a behaviour that is passed on through the genes.
