Genetic investigation of mouth asymmetry and lateralized (handed) foraging behavior in the scale-eating cichlid fish, Perissodus microlepis, from Lake Tanganyika, Africa

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Morphological variation plays a crucial role in the ecology and evolution of natural populations. One particularly interesting morphological polymorphism is left-right asymmetry, where individuals within a species conspicuously differ in their bilateral symmetry. The scale-eating cichlid fish, Perissodus mi-crolepis, from Lake Tanganyika has attracted much attention from evolutionary biologists since the ecological effects of their lateralized mouth were first documented in a publication in Science in 1993. This species comes in two morphs: one with a mouth that is turned to the right (‘right’ morph) and the other with a mouth that is directed towards the left (‘left’ morph). This mouth asymmetry is strongly associated with lateralized (handed) foraging behavior in that right morphs preferentially scrape scales from the left flanks of prey fish while left morphs forage from the right flanks. However, the mechan-isms that determine the mouth asymmetry and lateralized foraging behavior and the forces that drive the co-evolution of these morphological and behavioral traits remain largely unknown. The proposed research has three main goals to determine: (1) the extent, bimodality and ontogenetic timing of mouth asymmetry in P. microlepis, (2) the genetic bases of mouth asymmetry and (3) the effect of phenotypic plasticity on mouth asymmetry and handed foraging behavior. This project will greatly contribute to a deeper understanding of this textbook example and the basis of left-right asymmetry in animals more generally.