• The Korean Journal of Malacology
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• v.29 no.2
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• pp.113-120
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• 2013

The reproductive cycle, gonad index, condition index, and the sex ratio in female and male Coecella chinensis, which were collected from the coastal waters of Namhae, the South Coast of Korea, were investigated by histological analysis and morphometric data. Monthly variations of the gonad index and condition index of this species showed similar patterns to that of the reproductive cycle. The reproductive cycle in female and male C. chinensis can be classified into six successive stages: early active stage (April), late active stage (May), ripe stage (June), partially spawned/spent stage (June to August), degeneration stage (August) and inactive stage (September to March). According to monthly changes in relative frequency distributions of ovarian egg diameters of this species, in particular, a number of ripe eggs ranging about 70 ${\mu}m$ appear in June, however, in July and August, although the mode of egg diameters ranging about 50 ${\mu}m$ appear about 80%, these ripe eggs ranging from 60 ${\mu}m$ to 70 ${\mu}m$ are gradually decreased during the period from June to August. Therefore, the spawning period of this species is continued from June to August with a peak between July and August when the seawater temperature exceeds about $24.5^{\circ}C$. The sex ratio of female and male individuals was not significantly different from 1:1 (${\chi}^2$=1.20, p>0.05). No hermaphrodites were found.