Size-assortative copulation in the simultaneously hermaphroditic pond snail Radix auricularia (Gastropoda: Pulmonata)

Abstract

To better understand the importance of body size in hermaphroditic mating, we studied the mating behaviour of the pond snail Radix auricularia. This simultaneous hermaphrodite exhibits a positive correlation between body size and egg production and provides weak evidence for size-assortative mating. In addition to this mating pattern, the partner performing the male role was significantly smaller than the mounted partner, performing the female role. In this study, two laboratory experiments were done to test whether body size has (1) an effect on mate choice of the sperm donor, and (2) poses mechanical constraints. These snails did not display physical limitation in mating with a much larger or smaller partner. In the mate choice experiment, we found no evidence for significant preferences for large partners. Therefore, mate choice of sperm donor and mechanical constraints are not likely to contribute to the formation of size-assortatively mating pairs in this species, which contributes to understanding about how these processes work in hermaphrodites.