Annual reproductive cycle of the Chinese Anapella clam, Coecelle chinensis (Bivalve: Mesodesmatidae) using image analysis in Jeju, Korea
2002
Kang, D.H. | Choi, K.S. (Cheju National Univ., 1 Ara 1-Dong, Jeju 690-756 (Korea). School of Applied Marine Science)
The Chinese Anapella clam, Coecella chinensis are widely distributed on intertidal sand flats along the coast of Jeju Island in Korea. Limited information has been reported on their reproductive biology despite their natural abundance. This study is the first report on the annual reproductive cycle of the C. chinensis present at a beach on east coast of Jeju. Seasonal changes in the gonadal tissue development of the clam were investigated from July 1999 to July 2000 on a monthly bases. 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 early active, late active, mature, partially spawned, spent and indeterminate stages based on histological observation. Image analysis was applied on the histologically prepared cross-sections of the gonadal tissues. Mean oocyte diameter and percent egg area (PEA) in a follicle were quantified from digitized microscopic image of the cross-sections using a personal computer equipped with an image analyzer. Planimetrical methods applied in this study provide objective and truly quantitative information on reproductive status of the clam. Water temperature in this area seasonally fluctuated from 11 to 35 deg C and salinity varied from 17 to 18% annually. Gametogenesis was found to start in early April when water temperature reached 13 deg C. In mid-June, most of the clams were at the late active stages. Fully matured eggs were observed in July and Aug. Mean oocyte diameter fluctuated from minimum value of 10.3 plus or minus 2.1 micro m in May to maximum value of 16.4 plus or minus 1.3 micro m in July. The PEA values were also correlated with the gonad development stages: 63.5 plus or minus 7.3 in July, 41.7 plus or minus 9.3 in Aug and 29.6 plus or minus 11.5 in Sept. Spawning activities of most clams were observed from late July to Aug and Sept. Clams collected in Nov to March displayed spent and indeterminate gonad. Spawning peak of C. chinensis in the study area coincides with the high water temperature in summer season
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