Body size influences mating strategies in a simultaneously hermaphroditic sea slug, Aplysia vaccaria

The relationship between body size and hermaphroditic mating strategies was studied by following a population of the sea slug, Aplysia vaccaria, for one year. Fourteen individuals were tagged with internal microchips, and all mating pairs were weighed. Tagged individuals mated repeatedly both as sperm recipients and sperm donors. There was a trend toward size-assortative mating and size-assortative spatial clustering, and animals acting as females were larger than the average mass for the population. These findings support prior studies showing an association between larger relative size and sperm recipient roles in hermaphroditic gastropods, and highlight the need for critical experiments to determine the mechanisms of role choice and mate choice.