Meeting Abstract
The ability of simultaneous hermaphrodites to self-fertilize (selfing) can be advantageous as it can ensure reproductive success even when partners are rare. However, self-fertilization can lead to inbreeding depression due to low genetic variability, which reduces offspring fitness. Ctenophores (comb jellies) are a group of gelatinous marine predators that are almost entirely simultaneous hermaphrodites capable of selfing. In the ctenophore Mnemiopsis leidyi, selfing results in low offspring development and viability. Thus, there may be strong selective pressures to promote out-crossing and reduce selfing. In this study, we examine whether M. leidyi can avoid selfing using two potential mechanisms that promote out-crossing: sperm storage and egg trading. Conspecific sperm storage would allow M. leidyi to produce out-crossed offspring even when reproductively isolated. We sequenced the offspring of a single isolated individual and found genetic diversity consistent with more than one parent. To test this further, we isolated and spawned individuals for seven consecutive days and conducted paternity analyses on the resultant offspring. This design allowed us to test the ability and duration of sperm storage as well as the frequency of sperm storage within the population. Egg trading occurs when paired simultaneous hermaphrodites reciprocally alternate between shedding eggs and sperm. To test for this behavior, we placed paired M. leidyi on opposite sides of a porously divided tank. We found that the number of eggs spawned was highly skewed towards one member of each pair, suggesting that M. leidyi alter their reproductive output when spawning in close proximity to another individual. Taken together, these results provide insights into M. leidyi reproductive behavior, which is essential to understanding their ecology.
