Isognomon ephippium,withspecial lurid pearllayer,is a potentialaquaculture breed to cultivate specialcolor specialpearl. The historical identification of gonad development and reproductive cycle was important for breeding and pearl cultivation inI. ephippium. The development of gonad inI. ephippium was analyzed by histological sections technology. The data indicated that the development of both male and female gonads ofI. ephippium was devided into the proliferation stage,increasing stage, maturation stage,breeding stage and suspensive stage,with specific characteristics of gonads and germ cells. In the proliferation stage,oogonium and spermatogonium were produced in new follicles.In increasing stage,the area of the gonads,the number of follicles and germ cells were increased obviously. Massive oocytes and spermatocytes existed in follicles. In maturation stage,the follicles were filled with oocytes,which had bright germinal vesicle,clear nucleolus,and sperms with red tails. In breeding stage,mature germ cells were released from damaged follicles. In suspensive stage,follicles were shrinked and no germ cells were found. The reproductive cycle ofI. ephippium was one year,including proliferation stage from May to June,increasing stage from July to August,maturation stage from August to September,breeding stage from September to October,suspensive stage from October to November. Most gonads did not grow from December to next April.%通过石蜡切片对扁平钳蛤进行性腺发育组织学观察，结果表明，扁平钳蛤雌雄性腺的发育都可分为增殖期、生长期、成熟期、排放期和休止期5个时期。增殖期为滤泡形成期，出现了精原细胞和卵原细胞，贴近滤泡壁分布；在生长期，性腺面积、滤泡数目和生殖细胞数目都明显增大，卵母细胞和精母细胞形成；成熟期雌性滤泡内充满卵细胞，其生发泡透亮，核仁清晰可见，雄性滤泡内充满着蓝紫色的精子，精子尾部聚集在滤泡中央，呈鲜红色；排放期滤泡破损，卵细胞和精子排放，性腺面积减小；休止期滤泡腔萎缩，基本无生殖细胞残留。扁平钳蛤生殖周期为一年，5—6月处于性腺发育增殖期；7—10月性腺进入繁殖期，包括生长期、成熟期和排放期；11月进入休止期；其他月份性腺基本不发育。
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