Mouth dimorphism in scale-eating cichlid fish from Lake Tanganyika advances individual fitness

Random asymmetry, that is the co-existence of left- and right-sided (or -handed) individuals within a population, is a particular case of natural variation; what triggers and maintains such dimorphisms remains unknown in most cases. Here, we report a field-based cage experiment in the scale-eating Tanganyikan cichlid Perissodus microlepis (Boulenger, 1898), which occurs in two morphs in nature: left-skewed and right-skewed individuals with respect to mouth orientation. Using underwater cages stocked with scale-eaters and natural prey fish, we first confirm that, under semi-natural conditions, left-skewed scale-eaters preferentially attack the right flank of their prey, whereas right-skewed individuals feed predominantly from the left side. We then demonstrate that scale-eaters have a higher probability for successful attacks when kept in dimorphic experimental populations (left- AND right-skewed morphs together) as compared to monomorphic populations (left- OR right-skewed morphs), most...随机不对称性，即种群内同时存在左侧偏侧（或左利手）与右侧偏侧（或右利手）的个体，是自然变异的一种特殊情形；目前在绝大多数情况下，这类二态性的触发与维持机制仍不明确。本研究针对坦噶尼喀湖食鳞慈鲷——小鳞奇齿丽鱼（Perissodus microlepis，Boulenger, 1898）开展了野外笼养实验，该物种在自然环境中存在两种形态：依口部朝向区分的左偏型与右偏型个体。本研究使用投放了食鳞慈鲷与天然猎物鱼类的水下笼舍，首先证实：在半自然环境下，左偏型食鳞慈鲷会优先攻击猎物的右侧体侧，而右偏型个体则主要从猎物左侧取食鳞片。随后我们证实，与单态实验种群（仅含左偏型或仅含右偏型个体）相比，当食鳞慈鲷处于双态实验种群（同时包含左偏型与右偏型个体）中时，其攻击成功率显著更高，most...