To explore the histological and ultrastructural changes of the annual development of the testis and spermatogenesis of Lutraria sieboldii in Beibu Gulf of Guangxi,the annual development of testis and ultrastructure of spermatozoa of L.sieboldii were studied through tissue section,scanning and transmission electron microscopy.Results showed that the testis completes a cycle in one year,which can be divided into proliferating stage,growing stage,maturing stage,spawning stage and resting stage.The spawning was from December to April of the following year,and the testis development of 5%～10%individuals in each stage was slightly delayed.Spermatogenesis can be divided into proliferation period,growth period,mature period and metamorphosis period.The male reproductive cell can be divided into Spermatogonia stage,primary spermatocyte stage,secondary spermatocyte stage,spermatocyte stage and mature sperm stage.The sperm of L.sieboldii belongs to the flagella type,whose total length is(39.76±0.50)μm.The sperm head was composed of a nearly subelliptic spermatic acrosome and nucleus,the bottom of the acrosome and the spermatozoa connected with the spermatozoa were depressed to form a subacrosomal cavity.The electron density in the nucleus was uniform,and there was a gap in the middle of the nucleus.There are four mitochondria around the centriole complex to form the middle part of sperm,and the mitochondria are nearly round with apparent internal ridge.The plasma membrane wraps around the axial filaments to form sperm tail,and the"9 + 2"doublet microtubule structure can be clearly observed in the transverse section of the tail.In addition,there are two different types of spermatogonia:type A spermatogonia has no nucleolus in the nucleus while type B spermatogonia has nucleolus in the nucleus,and type B spermatogonia is distributed in the testis at different stages.

In order to investigate the efficient nursery culture mode and reasonable breeding density of Lutraria sieboldii, we had carried out an experiment at three different beaches in Beibu Gulf, Guangxi Province (Beihai, Qinzhou and Fangchenggang) using the same density gradient from February 2021 to April 2022. Two nursery culture modes, box and basket, were employed, followed by adult culture in baskets to compare the growth performance and survival rate of L. sieboldii at each stage. The results indicate that the box culture mode was more effective than the basket culture mode in Beihai and Fangchenggang, while the basket culture mode was more suitable for Qinzhou. The appropriate densities in Beihai, Fangchenggang and Qinzhou were 1 500, 1 000 grains·box−1 and 500 grains·basket−1, respectively. At the adult culture stage, the appropriate density in Beihai was 40 grains·basket−1, and the survival rates at the end of the culture period in Qinzhou and Fangchenggang were 0. The results show that the changes of water temperature, beach temperature, salinity, pH and dissolved oxygen (DO) in Beihai are the smallest and the water quality environment is the most stable. Besides, the water quality environment in Qinzhou and Fangchenggang changes greatly and is unstable. The sediment particle size of Beihai beach is dominated by coarse sand and medium sand, whereas Fangchenggang and Qinzhou beaches is dominated by medium sand and fine sand, and Qinzhou beach is dominated by fine sand. The results of phytoplankton survey indicate that Beihai has the highest quantity and diversity of algae, followed by Fangchenggang and Qinzhou. Thus, it is showed that L. sieboldii is suitable for nursery culture in both Beihai and Fangchenggang sea areas, and for adult culture in Beihai sea area.

In order to explore the suitable breeding density and effective culture mode of Tapes dorsatus in three sea areas of Beibu Gulf, Guangxi, we had carried out basket nursery culture, basket adult culture and net cage hanging experiments of T. dorsatus in mudflat of three sea areas in Qingzhou, Beihai and Fangchenggang from May 2021 to January 2023. The results show that: 1) The suitable nursery culture density for T. dorsatus were 2 000, 1 500 and 1 500 grains·basket−1, respectively, and the growth indexes and survival rate of T. dorsatus decreased with the increase of nursery culture density. The survival rates of all density groups in Beihai were significantly better than those in Fangchenggang and Qinzhou (P<0.05). Except that the growth indexes (Shell length, shell width and body mass) in d5 group (3 000 grains·basket−1) in Beihai were lower than that in Fangchenggang, the growth indexes of other groups were all higher than those of Fangchenggang and Qinzhou. 2) The suitable culture densities of T. dorsatus in Beihai, Fangchenggang and Qinzhou were 40, 40 and 20 grains·basket−1, respectively. The growth indexes and survival rate of T. dorsatus at adult stage were Beihai>Fangchenggang>Qinzhou, and the survival rate decreased with the increase of cultivation density. When the density of net cage suspension in Fangchenggang was 30 grains· cage−1, all growth indexes were the highest. There were no significant differences in shell length, shell width, shell height, body mass and survival rate among different density groups in net cage suspension (P>0.05). The results of environmental factors show that the water temperature, beach temperature, salinity, transparency, pH and DO in Beihai were slightly higher than those in Fangchenggang and Qinzhou, with relatively stable water quality. The water quality environment in Qinzhou and Fangchenggang changed greatly and was unstable. The diameter of plasmid at the bottom of Beihai mudflat was mainly coarse sand (49.00%), Fangchenggang was mainly composed of medium sand (59.28%), and Qinzhou was mainly composed of fine sand (77.33%). The results of phytoplankton quantity show that the species and quantity of phytoplankton algae in Beihai were the largest, and the least species and quantity of phytoplankton algae were in Qinzhou. The research indicates that T. dorsatus is suitable for nursery and adult culture in three sea areas of Beibu Gulf, and the breeding effect in Beihai is better than that in Fangchenggang and Qinzhou. Besides, 1.5-year-old T. dorsatus is suitable for net cage hanging culture in Fangchenggang sea area.

文章采用组织切片、透射电镜技术对广西北海营盘海域钝缀锦蛤(Tapes conspersus)的卵巢发育、卵子发生的组织学及卵黄发生的超微结构进行研究.结果显示,钝缀锦蛤卵巢发育一年为一个繁殖周期,分为增殖期(6月底-7月)、生长期(7月中旬-10月中旬)、成熟期(11月-翌年2月底)、排放期(3月-4月)、休止期(5月-6月)共5个时期.钝缀锦蛤卵巢发育受水温的影响较大,个体间的性腺发育并不完全同步.在广西北海营盘海域,钝缀锦蛤每年在6月底-7月初性腺开始发育,在翌年3月-4月底成熟的卵子大量排放.依据钝缀锦蛤卵细胞发育的相关特点,可将其划分为4个主要阶段,第一阶段为卵原细胞期,第二阶段为初级卵母细胞期,第三阶段为次级卵母细胞期,第四阶段为成熟卵母细胞期.根据透射电镜观察钝缀锦蛤卵黄的发生,可将其分为3个主要时期,第一时期为卵黄合成前期,第二时期为卵黄合成期,第三时期为卵黄合成后期.

为了解广西北部湾海域钝缀锦蛤(Tapes conspersus)精巢周年发育情况、精子发生过程及成熟精子超微结构,本文采用组织切片、扫描电镜、透射电镜技术对钝缀锦蛤精巢发育过程、精子的发生及超微结构进行了研究.研究结果显示:目前广西北部湾钝缀锦蛤未见雌雄同体情况,观察的个体皆为雌雄异体.一周年的采样结果中,雌性个体138个、雄性个体102个,雌雄的性比约为1.35︰1.1年即为精巢发育的一个周期,发育时期可以划分为增殖期、生长期、成熟期、排放期、休止期共5个主要分期.精细胞的发育可以划分为5个主要分期,即精原细胞期、初级精母细胞期、次级精母细胞期、精细胞期、成熟精子期.精子全长约59.27μm,属于鞭毛型,由头部、中部、尾部3个部分共同构成,精子头部呈圆锥型,由细胞核和顶体组成,顶体呈倒"V"型.电子在顶体的分布是不均匀的,顶体前部电子分布少,后部分布多.中部主要由两部分构成,即5个圆形排列的线粒体和一个中心粒复合体.轴丝与质膜两个部分共同构成了尾部,轴丝的双联体微管结构横切面表现为"9+2"型.此外,本实验观察到少部分精子尾部呈双尾结构.