Aspects of the Reproductive Activity of Cypraea caputdraconis from Easter Island (Mollusca: Gastropoda: Cypraeidae)

Abstract

Cypraea caputdraconis Melvill, 1888 (commonly known as pure), endemic to Easter Island, is an important mollusk in Easter Island handicrafts. Knowledge about its reproduction is necessary for sustainable management of this resource. Data presented here are from 14 monthly samples taken between 1989 and 1991. As in other species of the genus, C. caputdraconis populations sampled at Easter Island had a higher proportion of females (60.28%) than males. Females averaged slightly larger than males, but there was a large degree of size overlap between the sexes and lengths were not significantly different. Reproductive activity occurs year-round, as evidenced by the presence of all three gonadal stages at every sampling date, suggesting a reproductive cycle with continuous gametogenic activity, either lacking or with a very brief period of gonadal rest. Egg mass surveys indicate agreement between egg mass presence and gonadal maturity. Egg masses were recorded throughout the year. A decrease in the percentage of animals with egg capsules corresponded to a decrease in water temperature toward winter. Observations on behavioral sex expression in relation to brooding clearly point to the female as incubator, although in one instance a male was observed on the egg mass. The reproductive activity of the Easter Island pure may be tentatively characterized by a continuous reproductive cycle, with increased activity during spring and summer. We recommend closing this fishery during the period of peak reproductive activity to prevent overexploitation.