瘤背石磺两性腺周年发育规律的研究

Study on annual development of hermaphroditic gland of Onchidium struma

研究了江、浙、沪地区瘤背石磺(Onchidium struma)两性腺周年发育规律。结果显示,瘤背石磺雌雄同体,雄性先熟,生物学最小型为体长2.81cm,体质量1.81g。其两性腺发育为1年1个周期,发育经历增殖期、精子发生期、精卵同步发生期、排放期和休止期。其中排放期又分精子排放、精卵排放和卵子排放,体现了精卵发生的异时性。精子的发生包括精原细胞、初级精母细胞、次级精母细胞、精子细胞和精子;卵子的发生包括卵原细胞期、无卵黄期、卵黄形成期、卵黄形成后期和成熟期。成熟系数周年呈明显单峰分布,峰值出现在7～9月间;蛋白腺系数、卵黄腺系数与成熟系数具有一定的相关性,蛋白腺系数基本随着成熟系数变化而变化,卵黄腺系数随着成熟系数变化的过程中出现3个峰值,分别在6、8和12月。

We investigated the annual developmental rule of hermaphroditic gland of Onchidium struma from Jiangsu,Zhejiang and Shanghai.The results indicate that O.struma is a hermaphrodite,which often becomes a functional male before its female organs develop.The smallest individual is 2.81 cm in length and 1.81 g in weight.The development of hermaphroditic gland has a cycle per year,which is divided into proliferation,spermatogenesis,synchronous occurence of ova and sperm,exporting and resting stages.Specifically,exporting stage is divided into sperm exporting,simultaneous exporting of ova and sperm,and ova exporting,indicating a heterochrony of spermatogenesis and oogenesis.The male reproductive cells have spermatogonia,primary spermatocyte,secondary spermatocyte,spermatid and sperm.The female ones have oogonium,previtellogenic oocyte,vitellogenic oocyte,postvitellogenic oocyte and maturation.The annual change of gonadosomatic index （GSI） shows a unimodal distribution whose peak value occurs during July and September.The albumin gland index （AI） and vitelline gland index （VI） are correlated with GSI.AI changes along with GSI and has three peak values during GSI′s change,which occur in June,August and December,respectively.