Abstract
Ctenophores (comb jellies) are emerging as important animals for investigating fundamental questions across numerous branches of biology (e.g., evodevo, neuroscience and biogeography). A few ctenophore species including, most notably, Mnemiopsis leidyi, are considered as invasive species, adding to the significance of studying ctenophore ecology. Despite the growing interest in ctenophore biology, relatively little is known about their 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 cues and that body size significantly impacts spawning and reproductive output. Mnemiopsis leidyi adults that spawned alone produced a lower percentage of viable embryos versus those that spawned in pairs, suggesting that self-fertilization may be costly in this species. These results provide insight into the reproductive ecology of M. leidyi and provide a fundamental resource for researchers working with them in the laboratory.
Highlights
Ctenophores are fascinating planktonic animals most recognized by eight rows of fused cilia that they use as their primary means of locomotion
When placed in bowls overnight, we found no difference in spawning likelihood between ctenophores kept in constant light (20/21 [95%] spawned), four hours of darkness (15/15 [100%] spawned), eight hours of darkness (12/12 [100%] spawned), or constant darkness (17/18 [94%] spawned)
We found that M. leidyi individuals spawning alone had a lower percentage of developed offspring after 24 h than ctenophores that spawned in pairs (Fig. 6)
Summary
Ctenophores (comb jellies) are fascinating planktonic animals most recognized by eight rows of fused cilia that they use as their primary means of locomotion. Recent work suggests ctenophores are the sister group to the rest of all animals and are especially informative as to the state of the most recent common ancestor of animals (Dunn et al, 2008; Hejnol et al, 2009; Ryan et al, 2013; Borowiec et al, 2015; Chang et al, 2015; Whelan et al, 2015; but see Pisani et al, 2015) This phylogenetic position, the availability of nuclear and mitochondrial genome sequences (Pett et al, 2011; Ryan et al, 2013), and the ease with which embryos can be collected and observed (Pang & Martindale, 2008b) has made the ctenophore Mnemiopsis leidyi an emerging model. Mnemiopsis leidyi may even produce viable gametes as juveniles (Martindale, 1987)
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