Zimmerman Holger, Tolman Deryk, Reichard Martin
Institute of Vertebrate Biology, Czech Academy of Sciences, Květná 8, 603 00, Brno, Czech Republic.
Helsinki Institute of Life Sciences, University of Helsinki, Yliopistonkatu 3, 00014 Helsinki, Finland.
Behav Ecol. 2023 Apr 8;34(4):521-527. doi: 10.1093/beheco/arad024. eCollection 2023 Jul-Aug.
Brood parasites have demanding needs of host resources. Brood parasitic offspring are highly competitive and frequently cause the failure of host broods and the survival of a single parasitic offspring. Accordingly, virulent brood parasites lay a single egg in the same host nest to avoid sibling competition. In the cuckoo catfish (), which parasitize mouthbrooding cichlid fishes in Lake Tanganyika, the modes of host and parasite oviposition lead to frequent cases of multiple parasitism. We experimentally tested the prediction that multiple parasitism leads to frequent cannibalism among offspring. Cuckoo catfish embryos prey upon host offspring to obtain nourishment during their 3-week development in the host buccal cavity and may also consume conspecific embryos. The potential benefits of cannibalism in the system are, therefore, twofold; to decrease competition for limited resources (i.e., host brood with rich yolk sacs) and to directly obtain nourishment by consuming rivals. We found that cannibalism indeed provided measurable benefits in terms of increased growth of the cannibals, but cannibalism was rare and typically occurred once all host offspring had been consumed. This implies that cannibalism among cuckoo catfish embryos emerges to mitigate starvation rather than eliminate competition.
巢寄生者对宿主资源有很高的需求。巢寄生的后代竞争力很强，经常导致宿主巢的失败，只有一只寄生后代存活。因此，毒性较强的巢寄生者会在同一宿主巢中产下一枚卵，以避免同胞竞争。在寄生坦噶尼喀湖口孵丽鱼的杜鹃鲶中，宿主和寄生虫的产卵方式导致了频繁的多重寄生情况。我们通过实验验证了多重寄生会导致后代之间频繁发生同类相食的预测。杜鹃鲶胚胎在宿主口腔中发育的3周时间里，会捕食宿主后代以获取营养，也可能会吃掉同种胚胎。因此，在这个系统中，同类相食的潜在好处有两方面；减少对有限资源（即富含卵黄囊的宿主巢）的竞争，并通过吃掉对手直接获取营养。我们发现，同类相食确实在食人者生长增加方面带来了可衡量的好处，但同类相食很少见，通常发生在所有宿主后代都被吃掉之后。这意味着杜鹃鲶胚胎之间的同类相食是为了缓解饥饿，而不是消除竞争。
