Exp2_behaviour from Parasitic cuckoo catfish exploit parental responses to stray offspring

Interspecific brood parasitism occurs in several independent lineages of birds and social insects, putatively evolving from intraspecific brood parasitism. The cuckoo catfish, Synodontis multipunctatus, the only known obligatory non-avian brood parasite, exploits mouthbrooding cichlid fishes in Lake Tanganyika, despite the absence of parental care in its evolutionary lineage (family Mochokidae). Cuckoo catfish participate in host spawning events, with their eggs subsequently collected and brooded by parental cichlids, though they can later be selectively rejected by the host. One scenario for the origin of brood parasitism in cuckoo catfish is through predation of cichlid eggs during spawning, eventually resulting in a spatial and temporal match in oviposition by host and parasite. Here we demonstrate experimentally that, uniquely among all known brood parasites, cuckoo catfish have the capacity to re-infect their hosts at a late developmental stage following egg rejection. We show that cuckoo catfish offspring can survive outside the host buccal cavity and re-infect parental hosts at a later incubation phase by exploiting the strong parental instinct of hosts to collect stray offspring. This finding implies an alternative evolutionary origin for cuckoo catfish brood parasitism, with the parental response of host cichlids facilitating its evolution.This article is part of the theme issue ‘The coevolutionary biology of brood parasitism: from mechanism to pattern’.种间巢寄生（Interspecific brood parasitism）广泛存在于鸟类与社会性昆虫的多个独立演化支系，其演化起源普遍被认为源自种内巢寄生（Intraspecific brood parasitism）。布谷鲶（Cuckoo catfish，Synodontis multipunctatus）是目前已知唯一的专性非鸟类巢寄生生物，它寄生于坦噶尼喀湖（Lake Tanganyika）内的口孵慈鲷（mouthbrooding cichlid）种群，尽管其所属的倒立鲶科（Mochokidae）演化支系中并无育幼行为。布谷鲶会伴随宿主的产卵活动进行寄生，其卵随后会被亲代慈鲷收集并纳入口孵过程，但宿主后续可选择性排斥这些寄生卵。关于布谷鲶巢寄生的起源，存在一种演化假说：其源自产卵过程中对慈鲷卵的捕食行为，最终使得宿主与寄生生物的产卵行为在时空维度上形成精准匹配。本研究通过实验证实，在所有已知的巢寄生生物中，布谷鲶具备独特的生存策略：可在宿主完成卵排斥后的发育晚期再次感染宿主。研究表明，布谷鲶幼体可在宿主口咽腔（buccal cavity）外存活，并利用宿主强烈的亲代收集失散幼体的本能，在后续的孵化阶段再次感染亲代宿主。这一发现为布谷鲶巢寄生的演化起源提供了另一种全新的解释，即宿主慈鲷的亲代响应行为推动了该寄生策略的演化与定型。本文属于主题专辑‘巢寄生的协同进化生物学：从机制到模式’（The coevolutionary biology of brood parasitism: from mechanism to pattern）的组成部分。