A laboratory study of host use by the cuckoo catfish Synodontis multipunctatus

Abstract

The only known non-avian vertebrate obligate brood parasite is the cuckoo catfish (Synodontis multipunctatus), a Lake Tanganyikan endemic. The cuckoo catfish parasitizes Tanganyikan mouthbrooding cichlids, and under captive conditions, will also parasitize cichlids from other Rift Valley lakes. Here we examine the frequency of parasitism by the cuckoo catfish of Ctenochromis horei from Lake Tanganyika and three species from Lake Malawi and the greater Lake Victorian system in a laboratory setting. C. horei was parasitized significantly less (17%) than the allopatric species Haplochromis latifasciatus, Haplochromis nubilus, and Metriaclima estherae (combined parasitism rate of 28%). The lower rates of parasitism in C. horei may be due to differences in the mating ritual, oviposition (e.g., long periods of pseudospawning before actual oviposition), and behavioral adaptations (e.g., increased aggression towards the cuckoo catfish). The number of catfish eggs per parasitized brood was similar between C. horei, H. latifasciatus, H. nubilus, and M. estherae. Our results are comparable to findings from the field for C. horei parasitism frequency and number of cuckoo catfish per brood.We also analyzed the parasitism rate of the albino morph of Metriaclima zebra, a domestic strain.Parasitism rates and number of catfish per brood were the highest in the albino morphotype suggesting that the higher levels of parasitism may be related to lower aggressive behavior, lower visual acuity, or captive influence. Cuckoo catfish and mouthbrooding cichlids provide a model system for testing brood parasitism in a laboratory setting.

Parasitic cuckoo catfish exploit parental responses to stray offspring

“…Cuckoo catfish are considered an obligate brood parasite in the scientific literature (e.g. [16,18,21,22]), though evidence from the wild is indeterminate being based solely on the failure, thus far, to detect juvenile cuckoo catfish outside the care of their hosts [16]. Our own observations from captivity (M. Polačik, R. Blažek 2018, personal observation) and anecdotal information from fish hobbyists suggest that cuckoo catfish can occasionally reproduce without parasitizing cichlids, though whether outcomes in the benign environment of the aquarium necessarily translate to nature is clearly a question that needs to be addressed.…”

“…The catfish -cichlid system is also much more amenable to laboratory research, enabling substantial experimental manipulation [18,21,22]. Like many avian brood parasites, cuckoo catfish eliminate host progeny, though in the case of the cuckoo catfish this is achieved through direct predation [22]. Indeed, the cichlid host provides the parasite with both food and protection while incubation itself appears less critical compared with egg incubation in birds.…”

Early life-history features associated with brood parasitism in the cuckoo catfish, Synodontis multipunctatus (Siluriformes: Mochokidae)

“…Ctenochromis horei is a natural host of the cuckoo catfish and is parasitized in the wild [3]. The cuckoo catfish is a generalist brood parasite that infects different species of mouthbrooding cichlids, and in a laboratory setting will parasitize cichlids that are not native to Lake Tanganyika [4,20,21,49], such as Metriaclima zebra from Lake Malawi [50]. Cuckoo catfish were kept in aquaria with C. horei and a domestic albino strain of M. zebra.…”

“…The catfish lay their eggs and the female mouthbrooder picks them up to be incubated along with her own eggs. Even though host and parasite eggs are fertilized at the same time, the catfish develop faster and devour the host young (often completely eliminating the host brood) while still in the mouth of the cichlid mother [3,4,7,20,21].…”

“…Two recent studies on the cuckoo catfish system examined adult host responses to parasitism [20,21]. However, the ontogenetic features of the cuckoo catfish that enable this species to parasitize mouthbrooding cichlids have not been described.…”