Experience and relatedness influence mating interactions in a simultaneously hermaphroditic snail, Physa gyrina

Abstract

The means by which animals assess potential mates is an important issue in studies of reproductive systems. I tested whether an individuals previous experiences and the relatedness of mates affected mating behavior in a simultaneous hermaphrodite snail, Physa gyrina. Previous work with this species showed reduced reproductive success resulting from both strong outbreeding and inbreeding. Thus, I predicted that individuals should prefer partners of intermediate relatedness. During activity trials, snails moved longer distances when exposed to chemical cues from conspecifics of lesser relatedness. Furthermore, during mating interactions, behavioral responses to relatedness varied with gender-role: male-role behaviors did not vary across relatedness treatments, while snails paired with either closely related or highly dissimilar partners increased their female-role resistance behaviors as interactions escalated. Experiences with their current partner also affected behavioral dynamics. Familiar pairs had fewer matings and longer latency times until a mating occurred than unfamiliar pairs. Snails acting in the female role also exhibited higher resistance rates in familiar pairs than in unfamiliar pairs. Previous, brief exposure to chemical cues in a non-mating context also influenced behavior during a subsequent mating interaction. Snails that were previously exposed to chemical cues from unfamiliar individuals tended to be more likely to occupy the male role following an encounter, and had significantly lower copulation frequencies and higher female-role resistance rates (i.e. were choosier) than those previously exposed to cues from familiar individuals. Overall, the results show that: 1) relatedness, past exposure to conspecific chemical cues, and experience with a current partner all influence mating behaviors in these snails; and 2) in these simultaneous hermaphrodites, an individuals responses depend on whether it is occupying the male or female role.