The sex lives of ctenophores: the influence of light, body size, and self-fertilization on the reproductive output of the sea walnut, Mnemiopsis leidyi

Ctenophores (comb jellies) are emerging as important animals for investigating fundamental questions across numerous branches of biology (e.g., evodevo, neuroscience. and biogeography). Several ctenophore species including, most notably, Mnemiopsis leidyi, are known as invasive species, adding to the importance of studying the ecology of these animals. Despite the growing interest, relatively little is known about ctenophore reproduction. Like most ctenophores, M. leidyi is a simultaneous hermaphrodite capable of self-fertilization. In this study, we assess the influence of light on spawning, the effect of body size on spawning likelihood and reproductive output, and the cost of self-fertilization on egg viability in M. leidyi. Our results suggest that M. leidyi spawning is more strongly influenced by circadian rhythms than specific light clues, and that body size significantly impacts spawning and reproductive output. We also find a lower percentage of viable embryos from M. leidyi that were spawned alone versus those that were spawned in pairs, suggesting that self-fertilization may be costly in these animals. These results provide critical insight into the reproductive ecology of these ctenophores and provide a fundamental resource for researchers working with M. leidyi in the laboratory.