A complex mode of aggressive mimicry in a scale-eating cichlid fish

Aggressive mimicry is an adaptive tactic of parasitic or predatory species that closely resemble inoffensive models in order to increase fitness via predatory gains. Although similarity of distantly related species is often intuitively implicated with mimicry, the exact mechanisms and evolutionary causes remain elusive in many cases. Here, we report a complex aggressive mimicry strategy in Plecodus straeleni, a scale-eating cichlid fish from Lake Tanganyika, which imitates two other cichlid species. Employing targeted sequencing on ingested scales, we show that P. straeleni does not preferentially parasitize its models but —contrary to prevailing assumptions — targets a variety of co-occurring dissimilar looking fish species. Combined with tests for visual resemblance and visual modelling from a prey perspective, our results suggest that complex interactions among different cichlid species are involved in this mimicry system.

攻击性拟态是寄生或捕食性物种所采用的一类适应性策略，此类物种通过拟态与无害的模式物种高度相似，从而借助捕食获益提升自身适合度。尽管远缘物种间的相似性常被直观地与拟态现象相关联，但在诸多案例中，其确切机制与进化成因仍不甚明晰。本研究报道了坦噶尼喀湖食鳞丽鱼*Plecodus straeleni*所采用的复杂攻击性拟态策略，该物种会拟态另外两种丽鱼物种。通过对其摄食的鳞片开展靶向测序分析，我们发现*P. straeleni*并不会优先寄生于其拟态的模式物种——这与主流假设相悖——而是以多种同域分布、外形迥异的鱼类作为捕食对象。结合视觉相似性测试与猎物视角下的视觉建模分析，本研究结果表明，该拟态系统涉及不同丽鱼物种间的复杂相互作用。