Reproductive Cycle, Copulating Activity and Dispersion Pattern of the Dogwhelk Nucella freycineti (DESHAYES)
1993 Volume 1993 Issue 45 Pages 29-41
Details
1993 Volume 1993 Issue 45 Pages 29-41
KAWAI, KEI and SHIGERU NAKAO (Faculty of Fisheries, Hokkaido University). 1993. Reproductive cycle, copulating activity and dispersion pattern of the dogwhelk Nucella freycineti (DESHAYES). Benthos Research, 45 : 29-41.
The reproductive cycle of Nucella freycineti was studied based on samples collected at monthly intervals from September 1987 to December 1988 and from May 1990 to July 1991 in Usujiri, southern Hokkaido, Japan. The developmental processes of the gonads and the seminal vesicle were classified into four and three successive stages, respectively. The development of the gonads and the seminal vesicle exhibits a distinct annual cycle. In both sexes, remarkable gonadal development was observed during the warm season from June to October. More than 90% of the males were mature in October. However, oogenesis was observed through the winter until the next breeding season in April and May. The annual cycle of the ovary is not synchronous with that of the testis but with that of the seminal vesicle. Size at sexual maturity was 19+ mm and 15+ mm shell length for females and males, respectively. MORISITA index (Iδ) showed that these snails aggregated all year round. Strongest aggregation was observed during the colder and coldest seasons from November to May, when high copulation and breeding activities successively occurred. During warmer period from June to September, the index was relatively low but high foraging activity was observed.
