Seasonal changes in the gonadal development on the clam, Ruditapes philippinarum in Jeju, Korea
2002
Choi, K.S. | Koh, K.J. (Cheju National Univ., 1 Ara-Dong Cheju 690-756 (Korea). School of Applied Marine Science)
Seasonal changes in the gonadal development were studied in a high-tidal population of the clam, Ruditapes philippinarum living in the east coast of Jeju, Korea. Seasonal changes in the gonadal tissues of the clam were investigated monthly from May to Sept 2001. Shell length, height and tissue wet weight of the clams were recorded; the middle part of the body was sectioned longitudinally for histological analysis. The gonadal status of individual clam was then categorized into indifferent, developing, ripe, partially spawned and spent stages based on histological observation. Water temperature and salinity in the area fluctuated from 17.2 to 25.5 deg C and from 31.1 to 35.0%, respectively. Most of the clams collected in mid May were in different stages and developing stages. This indicated that gonadal development of the clams started in mid May when water temperature was 17.2 deg C. The gonads were at the developing stage during the month of June and most of them were matured in late June to early Aug. Fully mature eggs were dominant in mid July or early Aug. Microscopic examination showed simultaneous occurence of three different gonadal stages: developing, ripe and partially spawned, in late June to mid July. Spawning activities of the clams were observed from mid July to Sept. Spawning season of R. philippinarum in this study area occured during the summer season (from late July to Sept) when water temperature is 21 deg C and above
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