Role of population traits and local social interactions in sex-change plasticity of the protandric marine gastropod Crepidula coquimbensis

Theoretical and experimental work suggests that time to sex change in sequential hermaphrodites may be strongly linked to local population traits and the social environment of the individuals. We evaluated social control and temporal and spatial plasticity in the sex-change response of the protandric marine gastropod Crepidula coquimbensis, which inhabits the empty shells of other gastropods and reproduces via direct development. Over 2 yr, 2 populations with significant genetic distance were sampled, and the abundance, population sex ratio, and sex ratio within hosting shells was measured. Reproductive responses, minimum female size, and the size at which 50% of the males changed sex to female (L50) were calculated for each location and sampling date. The sex ratio was male-biased in all cases. High temporal and spatial variability in the abundance, sex ratio, and body size at sex change was observed. However, negative and significant correlations were found between minimum female size and number of males in the aggregation and between population sex ratio and L50. Although earlier studies have suggested that sexchange strategy of gastropod species with direct development is less plastic and responsive to conspecifics, the present work indicates that the protandric marine gastropod C. coquimbensis may adjust its sexual strategy to local social conditions.