Annual gametogenesis of the Chinese anapella clam Coecella chinensis (Deshayes 1855) at an upper intertidal sandy beach on the east coast of Jeju, Korea

Abstract

We report for the first little annual gametogenesis in the Chinese anapella clam Coecella chinensis (Deshayes 1855) living on all Upper intertidal sandy beach oil the eastern coast of Jeju. Korea. Using histological methods, gonadal maturation. oocyte area in the follicle (follicle index. FI). and oocytc diameter were investigated. Gametogenesis began in the middle of April when the sediment temperature was 13 degrees C. Annual inaxiluLlin oocyte size and FI peaked ill July when Water temperature reached 20 degrees C and sediment temperature reached 35 degrees C. Subsequent spawning of C. chinensis Occurred ill August and continued until the end of September. Mean ripe oocyte diameter was 3 1.2 mu m, which is comparatively smaller than that of other bivalves. Clams over 15.7 mm in shell length had mature gonads, indicating that this size is a biological minimum for reproduction. Annual sediment temperature fluctuation was positively correlated with condition and gonadal development (P < 0.01), indicating that cyclic changes in gametogenesis are in part governed by Substrate temperature. The relatively smaller eggs observed here are believed to be a reproductive strategv of C. chinensis, all adaptive trade-off between reproduction and growth in the food-poor upper inteitidal environment.