Sexual dimorphism of Nucella lapillus (Gastropoda: Muricidae) in North Wales, UK

Abstract

Multivariate statistical methods were employed to examine sexual dimorphism in size and shape of Nucella lapillus collected from 16 sheltered sites along coasts of Anglesey and the Lleyn Peninsula, North Wales, UK. Females were significantly larger than males in overall size; among 12 relative measures of shell shape, two ratios (shell width/shell length and aperture length/shell length) were significantly different between males and females, but these differences usually decreased with increasing age (shell length). The observed hypoallometric dimorphism could be a result of selection on increased female fecundity, which may be positively correlated with shell size in N. lapillus as in other gastropod species.