Mate choice is not affected by mating history in the simultaneously hermaphroditic snail Lymnaea stagnalis

Abstract

Mate choice based on mating history is one way to optimize the distribution of one's sperm. This is especially pertinent when donating semen is costly. Owing to sperm competition many species allocate different amounts of sperm depending on their partners' mating histories. The hermaphroditic Lymnaea stagnalis has a preference for inseminating different partners, rather than the same one twice. Moreover, virgin partners receive more sperm than nonvirgins. Here we aim to determine whether these hermaphrodites prefer to inseminate virgins. Therefore, focal animals were offered a choice between one mating partner raised in isolation and one raised in a group. For each rearing condition we also measured individual growth, onset of egg laying (waiting time) and hatching success. Of the growth parameters we found that only the asymptotic size differed, with the virgins attaining a larger size. This coincides with the delayed onset of laying selfed eggs by virgins. Selfed eggs did not differ in hatching success from outcrossed eggs. The choice experiment revealed that focal individuals mated randomly with animals raised in isolation (virgins) and raised in groups (nonvirgins). This leads us to conclude that the decisions about whether to mate with an encountered individual and how much sperm to donate to this individual are two separate processes. © The Author 2008. Published by Oxford University Press on behalf of The Malacological Society of London, all rights reserved.