Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Scale-eating cichlids: from hand(ed) to mouth. | Palmer Journal of Biology 2010 9 11 http content 9 2 11 Journal of Biology MINIREVIEW Scale-eating cichlids from hand ed to mouth A Richard Palmer See research article http 1741-7007 8 8. Abstract Two recent studies in BMC Biology and Evolution raise important questions about a textbook case of frequency-dependent selection in scale-eating cichlid fishes. They also suggest a fascinating new line of research testing the effects of handed behavior on morphological asymmetry. The twisted smiles of left- and right-bending scale-eating cichlids Figure 1 have achieved near-legendary status among evolutionary biologists since their explosion onto the scene in 1993 1 . As more data have accumulated though the story has become both more interesting and decidedly more puzzling. Two recent papers by Stewart and Albertson in BMC Biology 2 and Van Dooren et al. in Evolution 3 add valuable new perspectives including the exciting possibility that handed behavior may amplify mouth asymmetry during growth. But these and other studies also raise important questions about this textbook case of frequency-dependent selection. The original story 1 is inescapably seductive because it makes sense and is easy to tell. Perissodus microlepis is a specialized scale-eater from Lake Tanganyika that nips scales off the posterior flanks of larger prey fish. Their mouths bend to one side of the head which allows them to strike from a more posterior orientation that makes them less visible to intended victims. Mouths bend to the right in some individuals and to the left in others and a single locus two-allele polymorphism is thought to control the direction of mouth-bending with right bending being dominant. Finally frequencies of right- and left-bending individuals appear to vary cyclically around 50 50 over time as if negative frequency-dependent selection were maintaining this polymorphism. So the logic goes when right-bending individuals become more common .
