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

形态变异在自然种群的生态和进化中起着至关重要的作用。一种特别有趣的形态多态是左右不对称，即物种内的个体在两侧对称性上明显不同。自1993年《科学》杂志首次报道了坦噶尼喀湖食鳞鱼Perissodus microcroepis的嘴巴偏侧的生态效应以来，这种鱼一直受到进化生物学家的极大关注。这个物种有两种变形：一种是嘴巴向右转(“右”型)，另一种是嘴朝左(“左”型)。这种嘴巴的不对称性与偏侧(手)觅食行为密切相关，因为右侧的变种优先从猎物的左侧刮鳞，而左侧的变种从右侧觅食。然而，决定嘴巴不对称和偏侧觅食行为的机制以及驱动这些形态和行为特征共同进化的力量在很大程度上仍不清楚。这项研究有三个主要目标：(1)小鳞鱼嘴不对称的程度、双峰性和个体发育时间；(2)口不对称的遗传基础；(3)表型可塑性对嘴不对称和手觅食行为的影响。这个项目将极大地有助于更深入地理解这个教科书上的例子，以及更普遍的动物左右不对称的基础。

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.