Abstract
Background: While bilaterality is a defining characteristic of triploblastic animals, several assemblages have managed to break this symmetry in order to exploit the adaptive peaks garnered through the lateralization of behaviour or morphology. One striking example of an evolved asymmetry in vertebrates comes from a group of scale-eating cichlid fishes from Lake Tanganyika. Members of the Perissodini tribe of cichlid fishes have evolved dental and craniofacial asymmetries in order to more effectively remove scales from the left or right flanks of prey. Here we examine the evolution and development of craniofacial morphology and laterality among Lake Tanganyika scale-eating cichlids.Results: Using both geometric and traditional morphometric methods we found that the craniofacial evolution in the Perissodini involved discrete shifts in skeletal anatomy that reflect differences in habitat preference and predation strategies. Further, we show that the evolutionary history of the Perissodini is characterized by an accentuation of craniofacial laterality such that certain taxa show elaborate sided differences in craniofacial shape consistent with the sub-partitioning of function between sides of the head during attacks. Craniofacial laterality in the scale-eating specialist Perissodus microlepis was found to be evident early in development and exhibited a unimodal distribution, which is contrary to the adult condition where jaw laterality has been described as a discrete, bimodal antisymmetry. Finally, using linkage and association analyses we identified a conserved locus for jaw handedness that segregates among East African cichlids.Conclusions: We suggest that, during the evolution of the Perissodini, selection has accentuated a latent, genetically determined handedness of the craniofacial skeleton, enabling the evolution of jaw asymmetries in order to increase predation success. Continued work on the developmental genetic basis of laterality in the Perissodini will facilitate a better understanding of the evolution of this unique group of fishes, as well as of left-right axis determination among vertebrates in general.
| Original language | English (US) |
|---|---|
| Article number | 8 |
| Journal | BMC Biology |
| Volume | 8 |
| DOIs | |
| State | Published - Jan 26 2010 |
| Externally published | Yes |
Bibliographical note
Funding Information:This work was supported by the Biology Department at Syracuse University, the Reneé Crown Honors Department and the McNair Undergraduate PostBaccalaureate Achievement Program. We would like to thank J T Streelman and N Parnell for providing the most recent Malawi cichlid linkage map for use in this study. We would also like to thank S Renn and H Hofmann for providing the collection of P. microlepis specimens from the field. Finally, we thank four anonymous reviewers, as well as J T Streelman, T D Kocher, K A Parsons and W J Cooper, for reading and commenting on earlier drafts of this manuscript.