Choosy males in a littorinid gastropod: male Littorina subrotundata prefer large and virgin females

Abstract

Mate choice has been considered to be a uniquely female behaviour. However, recent studies suggest that males strategically allocate their sperm among females with the greatest reproductive value. We investigated mating behaviour in the direct-developing Northern Pacific gastropod, Littorina subrotundata. Our field survey showed significant sexual dimorphism and the presence of size-assortative mating in our study population. Laboratory studies demonstrated that larger males may physically out-compete smaller males for access to females. Additional laboratory mate-choice experiments showed that males preferentially copulated with larger females. We also found that males were significantly more likely to copulate with virgin females than with females that had recently copulated. This suggests that males can detect the presence of sperm from rival males within a female's reproductive tract.