Abstract
The mode of reproduction and development of the muricid snail, Muricodrupa fusca, which inhabits tide pools was investigated on the Pacific coast of central Japan. This species has direct development and produces a small number of large eggs compared with the related species Thais clavigera. M. fusca breeds from March to August leaving egg capsules in small crevices in tide pools. During mating behavior, males mount females for many hours, but the duration of copulation seems to be short. Females of M. fusca are much larger than their mates, and the size ratio of female to male is greater than that of T. clavigera. Adaptive implications of their mode of reproduction and development are discussed with reference to the environmental conditions of tide pools in which the risk of desiccation and predation seems to be small.
