Adoption and Risk Management in Fish: How Cichlids Prevent Their Young from Being Eaten

Mar. 19, 2013 — For a variety of reasons, many humans choose to adopt children. More surprisingly, adoption is fairly widespread in the animal kingdom, even though it would seem to counteract the basic premise of Darwin's theory of evolution, which suggests that animals should raise as many of their own offspring as possible. Understanding the rationale for adoption has challenged theorists for generations. Franziska Schaedelin and colleagues at the University of Veterinary Medicine, Vienna now describe a new approach to the problem. The scientists present findings that suggest parents of fish exchange young with other parents to reduce the chances that their entire brood will be predated.

The results are published in the current issue of the journal Behavioral Ecology.

The phenomenon of adoption has taxed the minds of evolutionary scientists since Darwin first came up with his account of natural selection. According to Richard Dawkins's description, adoption is "a double whammy. Not only do you reduce, or at least fail to increase, your own reproductive success, but you improve someone else's." So why are animals apparently so willing to take care of young that are not related to them?

Franziska Schaedelin and colleagues at the Konrad Lorenz Institute of the University of Veterinary Medicine, Vienna now shed interesting light on the problem. The researchers are investigating a small cichlid fish that lives in Lake Tanganyika in southern Africa. The species is monogamous and pairs construct nesting caves to protect their eggs and fry from predators. By diving 12 meters to the lake floor, the scientists were able to collect DNA samples from over 350 parents and fry from over 30 nests. Sophisticated genetic techniques were then applied to investigate the parentage of fry in individual nests.

Continued: http://www.sciencedaily.com/releases/2013/03/130319091129.htm