日本海における雄ズワイガニの最終脱皮について

Abstract

The terminal molt of the male snow crab Chionoecetes opilio was studied using 1, 638 male crabs with a carapace width larger than 60mm caught by Danish seine, trap and beam trawl in the Japan Sea from August 1989 to October 1990. For estimation of the molting stages of male crabs, the second maxilla was taken, and the carapace width and chela height of each individual was measured. In examination of the relationship between carapace width and chela height, male crabs were divided into two groups, those with a relatively large chela height (large-clawed crabs), and those with a relatively small chela height (small-clawed crabs). In the small-clawed crabs, intermolt, premolt and postmolt stages were mainly observed from February to May, from June to September, and from September to October, respectively. On the other hand, almost all the large-clawed crabs were at the intermolt stage throughout the year, and the postmolt stage was observed from September to October. These results indicate that small-clawed crabs continue to molt once a year, whereas large-clawed crabs have already undergone the terminal molt.