广东鲂性腺发育组织学研究

利用组织学方法,对珠江下游野生广东鲂(Megalobrama terminalis)性腺进行了显微观察和研究,描述了其卵巢、精巢的结构特征以及各类型生殖细胞形态。结果显示,广东鲂属于一次性产卵类型,卵巢发育类型为部分同步型。其卵巢为细线或条状,卵巢发育经历卵原细胞期、单层滤泡细胞期、卵黄泡期、卵黄充满期、成熟期和退化期。卵细胞发生经历3个阶段:卵原细胞、初级卵母细胞和次级卵母细胞;卵巢初级卵母细胞中核仁外排现象出现在第2时相末期至第3时相早期;精巢呈线状或直棒状,精巢为叶状型结构。精细胞发生经历5个阶段:精原细胞、初级精母细胞、次级精母细胞、精子细胞及精子;繁殖季节精子充满于精小叶内,精小囊消失。     

双须骨舌鱼性腺发育的组织学观察

通过组织学研究方法,分别对双须骨舌鱼Ⅱ~Ⅴ期的卵巢及Ⅱ~Ⅵ期精巢的形态结构、特征及生殖细胞变化进行描述。结果显示,Ⅱ时相卵母细胞的细胞核较大,约为细胞体积的一半;Ⅲ时相卵母细胞出现卵黄斑及卵黄颗粒;Ⅳ时相卵母细胞中卵黄迅速积累且细胞膜出现褶皱;Ⅴ时相卵母细胞膜表面的褶皱消失。雄性双须骨舌鱼精巢发育的Ⅱ期,只含有初级精母细胞。Ⅲ期精巢分布有初级和次级精母细胞,精小管形成且小管中充满精细胞;Ⅳ期精巢主要含有初级和次级精母细胞以及精原细胞,精小管中出现空腔;Ⅴ期精巢中包含次级精母细胞、精原细胞和精子细胞,精小管中的空腔增大;Ⅵ期精巢则显示出高度血管化和结缔组织增多等特点。本研究将为双须骨舌鱼人工繁殖提供参考。     

脊尾白虾的性腺发育及组织结构观察

为系统研究脊尾白虾的性腺发育及组织学特征,采用常规的石蜡切片及H.E染色方法对脊尾白虾的性腺发育及其组织结构进行观察。结果表明,脊尾白虾的雌性生殖系统由卵巢、输卵管及排卵孔组成。卵子发生经历了卵原细胞、卵黄合成前期卵母细胞、内源性卵黄合成期卵母细胞、外源性卵黄合成期卵母细胞,最后发育为成熟的卵母细胞。卵巢发育可分为增殖期、小生长期、大生长期、成熟期及产后恢复期。脊尾白虾雄性生殖系统由精巢、输精管及排精孔组成。精巢由生精小管构成,不同生精小管内精子发育可不同步。精子发生经历了精原细胞、初级精母细胞、次级精母细胞、精细胞,最后发育为精子。输精管可分为前、中、后输精管及末端壶腹,精荚在输精管中形成。     

外源性促性腺激素诱导日本鳗鲡精子发生和成熟的作用机制

用兔抗血清对抗促黄体素生成素受体（LHR）或称绒毛膜促性腺激素受体（CGR）和雄激素受体（AR）进行LHR和AR免疫组织化学定位,以揭示外源性促性腺激素（鲤脑垂体激素和hCG）诱发日本鳗鲡精子发生及其内分泌机制。结果表明,经过注射激素处理后的实验组与注射前的对照组相比较,其精巢发育和精子发生出现十分显著的变化。组织学切片观察显示,激素处理前鳗鲡精巢处于精原细胞增殖期,而两种激素混合注射后第10天,实验组可见精小叶中精原细胞的有丝分裂和初级与次级精母细胞的数量显著的增加。注射后第35天,靠近生殖上皮除有少量精原细胞外,精小叶中有大量初级精母细胞和次级精母细胞和少数精子细胞以及管腔中存在少量精子。在注射后第83天,日本鳗鲡完成了精子发生和精巢发育成熟以及释精。免疫组织化学染色结果进一步揭示,激素处理前,LH受体免疫活性分布在生殖上皮,显示强的免疫阳性反应;激素处理后,LH受体定位在Sertoli细胞和间质细胞以及精原细胞和初级与次级精母细胞的胞膜上,均显示强的免疫阳性反应。激素处理前,雄激素受体定位在生殖上皮和早期生精细胞的胞膜上;激素处理后,AR则定位在这些生精细胞的核或胞质,而精子细胞和精子显示免疫阴性反应。这些结果首次证明了这两种激素诱导鳗鲡精子发生和成熟的作用机制是通过LH受体和雄激素受体的介导。     

长鳍吻鮈性腺发育的初步观察

采用常规石蜡切片技术对野生长鳍吻鮈(Rhinogobio ventralis(Sauvage et Dabry))性腺进行了组织学观察,描述了其各类型生殖细胞形态及卵巢、精巢的分期特征。结果显示:长鳍吻鮈卵巢为细线状或扁条状,精巢为细线状或直棍状;卵细胞发生经历了卵原细胞、初级卵母细胞和次级卵母细胞3个阶段,精细胞发生经历了精原细胞、初级精母细胞、次级精母细胞、精子细胞及精子5个阶段;性腺发育分为6个时期,卵巢中第Ⅱ时相晚期至Ⅲ时相早期的初级卵母细胞中出现核仁外排现象;同一时期卵巢中存在多种时相的卵母细胞,故推测其卵巢发育类型为部分同步型,精巢为小叶型结构。     

北方须鳅性腺发育的组织学观察

采用组织学方法观察辽宁太子河上游体长5~11cm的北方须鳅Barbatula nuda性腺发育的组织形态结构。结果表明:北方须鳅的精巢属于小叶形,分为6个发育期,精子的发生分为5个时相:精原细胞、初级精母细胞、次级精母细胞、精子细胞和成熟精子;卵巢发育分为6个时期,卵子的形成分为5个时相:卵原细胞、初级卵母细胞前期、初级卵母细胞后期、次级卵母细胞、成熟卵子。夏季水温较高时,北方须鳅迅速积累营养物质,精巢当年秋冬季节达到Ⅳ期,次年三、四月即可繁殖,较非冷水性鱼类提前1~2个月。     

粗唇鮠精巢显微结构和精子发生的研究

采用光镜和透射电镜观察了粗唇鮠(Leiocassis crassilabris)精巢结构和精子发生。光镜结果显示:粗唇鮠的精巢各小叶由数个小囊组成。从第Ⅱ期到第V期时,初级精母细胞逐渐发育成为次级精母细胞、精子细胞和精子,第Ⅵ期为排精后退化时期。透射电镜观察粗唇鮠的精原细胞、初级精母细胞、次级精母细胞、精子细胞和精子的形态以及细胞核和线粒体等的结果表明:在精子发生各期中线粒体和细胞核有明显的变化;精原细胞时期细胞器较丰富,到精子细胞后期,细胞器的形态和数量发生了较大变化;随着精母细胞的发育,核质凝聚程度逐渐增强;粗唇鮠的精子具有椭圆的头部和复杂的中片,并具有由外膜折叠形成的波浪形的结构。     

金钱鱼性腺发育及其组织结构观察

采用常规石蜡切片,H.E染色研究了金钱鱼性腺发育及组织结构特征.结果显示,2+龄的金钱鱼性腺发育成熟.金钱鱼精巢为管型,可分为:精原细胞增殖期、精母细胞生长期、精母细胞成熟期、精子细胞变态期、精子成熟期等5个时期.从Ⅱ期精巢起,金钱鱼精巢的成熟系数(GSI)为0.2％～1.5％,精巢成熟系数在发育到精子细胞成熟期(Ⅴ期)达到峰值,肝重指数(HSI)在精子细胞变态期(Ⅳ期)达到峰值.金钱鱼卵巢的卵母细胞发育过程可分为5个时相,相对应的卵巢发育亦分为5个时期.从Ⅱ期卵巢起,金钱鱼卵巢的成熟系数为1.2％～14.9％,在发育到Ⅴ期时达到峰值,HSI在Ⅳ期达到峰值.Ⅱ时相卵母细胞出现卵黄核和滤泡膜.Ⅲ时相卵母细胞中开始出现油滴,卵黄颗粒.Ⅳ时相卵母细胞中卵黄颗粒与油滴的数量迅速增多.Ⅴ时相卵母细胞中卵黄颗粒融合成片,在卵母细胞中卵黄颗粒与油球之间在数量上没有明显的差异.根据切片观察,Ⅴ期卵巢中,除了Ⅴ时相卵母细胞外,还有一定数量的Ⅱ、Ⅲ和Ⅳ时相卵母细胞,卵母细胞发育呈现非同步型.并且发现在多数产完卵后的卵巢中,除空的滤泡外亦存在一定数量的Ⅱ、Ⅲ和Ⅳ期卵母细胞,因此推测,金钱鱼的产卵类型为分批非同步产卵类型.     

粗唇(鱼危)精巢显微结构和精子发生的研究

采用光镜和透射电镜观察了粗唇(鱼危)(Leiocassis crassilabris)精巢结构和精子发生.光镜结果显示:粗唇(鱼危)的精巢各小叶由数个小囊组成.从第Ⅱ期到第V期时,初级精母细胞逐渐发育成为次级精母细胞、精子细胞和精子,第Ⅵ期为排精后退化时期.透射电镜观察粗唇(鱼危)的精原细胞、初级精母细胞、次级精母细胞、精子细胞和精子的形态以及细胞核和线粒体等的结果表明:在精子发生各期中线粒体和细胞核有明显的变化;精原细胞时期细胞器较丰富,到精子细胞后期,细胞器的形态和数量发生了较大变化;随着精母细胞的发育,核质凝聚程度逐渐增强;粗唇(鱼危) 的精子具有椭圆的头部和复杂的中片,并具有由外膜折叠形成的波浪形的结构.     

尼奥罗非鱼杂种性别类型与性腺发育初步研究

通过组织学方法,研究了0.5~4.5月龄尼奥罗非鱼杂种(尼罗罗非鱼♀×奥利亚罗非鱼♂)的性腺发育特征与性别类型。结果表明,0.5月龄尼奥罗非鱼原始性腺尚未分化;1月龄,精巢中原始生殖细胞开始分化成精原细胞;2.5月龄出现初级精母细胞;3月龄出现次级精母细胞;3.5~4月龄精巢中存在不同发育阶段的生殖细胞,壶腹空腔中分散着稀疏的精子;4.5月龄精巢壶腹腔内密集大量精子。在2.5、3.5、4、4.5月龄抽样中,均检测到雌鱼,2.5~3.5月龄卵巢以第Ⅱ时相卵母细胞为主;4~4.5月龄卵巢以第Ⅲ时相卵母细胞为主。研究结果初步表明,尼奥罗非鱼杂种中观察到雄性、雌性两种性别类型,以雄性性别为主;杂种雌、雄鱼的性腺均能正常发育。     

中东太平洋公海金枪鱼延绳钓误捕海龟的观察和分析

根据2006年2－11月科学观察员对热带东太平洋公海海域(05°N～10°S,134° W~173°W)金枪鱼延绳钓渔业的调查,期间共投钩223次(天),误捕到绿海龟、蠵龟、丽龟、玳瑁和棱皮龟5种共22尾,死亡海龟13尾。从海龟误捕率看,平均每次尾数为0.098 65。平均每千钩尾数0.037 40。从海龟的钩获部位看,喙(嘴)上钩占41.0%,躯干部位上钩占13.6%,喉部上钩占13.6%,前肢上钩占18.2%,主绳缠绕被捕获占13.6%。海龟的误捕区域位于04°S以北海域,几乎可全年捕获。此外分析了不同钩位误捕海龟的数量,探讨了影响误捕率和死亡率的因素,提出保护对策。     

Involvement of steroid hormones in the preovulatory gonadotropin surge in female goldfish

Goldfish,Carassius auratus, spawn several times within a spawning season. A gonadotropin (GtH) surge occurs at the time of ovulation in this cyprinid species. This ovulatory GtH surge mediates the processes of final oocyte maturation and ovulation, and occurs at the end of each spawning cycle. Within a cycle, there is a shift in the predominant plasma steroid from estradiol to testosterone, and finally 17α, 20β-dihydroxy-4-pregnen-3-one at the time of the ovulatory GtH surge. High levels of testosterone were always observed before ovulation. When ovariectomized or sexually regressed female goldfish were implanted with testosterone, they exhibited a GtH surge which was similar to those normally observed at ovulation. These results strongly suggest that elevated plasma testosterone is an important physiological requirement for the occurrence of the GtH surge.     

基于物种分布模型的全球绿海龟空间分布及洄游廊道预测

环境因素影响物种的空间分布和动态, 全面了解环境与物种分布之间的关系对于其资源的管理和保护至关重要。绿海龟(Chelonia mydas)作为典型的长距离迁徙物种, 周期性地往返于索饵地和繁殖地之间, 迁徙距离可达数千千米。物种分布模型(species distribution model, SDM)是研究环境因子信息和物种分布关系的有效工具, 可以通过环境因子数据有效模拟物种潜在分布区域。本研究结合绿海龟物种出现记录点和环境变量, 应用物种分布模型预测不同时间段的绿海龟分布情况, 得出其分布区域的时空变化, 推断洄游路线。结果表明: 离岸距离、深度和海洋表层温度对绿海龟分布起重要作用; 太平洋西部、印度洋北部和大西洋西部为绿海龟主要适宜栖息范围; 大西洋-地中海以及印度洋-太平洋之间存在绿海龟洄游通道。同时, 基于气候变化模拟了绿海龟 2050 年和 2100 年的潜在分布区域, 分布范围在印度洋中部、太平洋中西部海域减少, 在大西洋中部海域增加, 在全球范围内呈现向高纬度海域扩散的趋势。     

达氏鲟dmc1基因的克隆及在精子生成中的表达分析

DNA减数分裂重组酶1基因(disrupted meiotic cDNA,dmc1)是一个在减数分裂时期特异表达的基因,为减数分裂同源染色体配对所必需。为研究dmc1基因在达氏鲟(Acipenser dabryanus)不同组织的表达特征,从达氏鲟性腺转录组数据库搜索得到该基因并设计引物,克隆获得达氏鲟dmc1的编码区序列,其中开放阅读框(ORF)为1 029 bp,编码342个氨基酸。运用生物信息学方法分析达氏鲟dmc1基因编码的蛋白序列和系统进化关系,推测达氏鲟Dmc1蛋白的分子量为82.696 kDa,理论等电点(PI)为5.04;多重序列比对发现,Dmc1氨氮酸序列在进化中可能比较保守。系统进化分析显示,AdDmc1属于RecA家族Dmc1蛋白分支,且与四足动物类聚为一支。RT-PCR结果表明,dmc1基因在精巢和卵巢中特异表达。结合组织学结果通过实时荧光定量PCR研究dmc1基因在精子生成过程中的表达特征发现,dmc1基因在0~Ⅰ期精巢中不表达;在Ⅱ、Ⅲ、Ⅳ期精巢中,其表达量逐渐升高并在Ⅳ期精巢中达到最高;在Ⅴ期精巢中,其表达量显著性下降(P<0.05),因此推断达氏鲟dmc1基因可能是减数分裂时期特异表达的基因,研究结果可为后续达氏鲟初级和次级精母细胞的鉴定奠定基础。     

Incidental captures of sea turtles by swordfish and albacore longlines in the Ionian sea

ABSTRACT:   Incidental catches in pelagic longline fishing pose a serious threat to sea turtle populations throughout the world's seas and oceans. In this work, carried out in the framework of the EC-DG-Fisheries 98/008 project, information on sea turtle catch rates from swordfish and albacore longline fishing activities observed in Italian waters off the Ionian Sea during 1999 and 2000, are reported. In addition, biometric data, health status, and tagging return rate of sea turtles captured are provided. A total of 200 sea turtles were caught (198 loggerhead turtles and 2 green turtles), comprising 0.5–15.7% of the total catch in number of individuals. The estimates of the sea turtles caught by the total fishing effort of both longlines in the whole study area were 1084 specimens in 1999 (95% CI = 667–1502) and 4447 specimens in 2000 (95% CI = 3189–5705). Although all sea turtles were released alive, nearly half of them had hooks that could not be removed and remained deeply embedded in the digestive tract.     

Food-deprivation-induced suppression of pituitary–testicular-axis in the tilapia Oreochromis mossambicus

In the present study, the tilapia Oreochromis mossambicus were exposed to food deprivation for a period of 6 or 12 days and changes in the luteinizing hormone (LH) immunoreactivity in the proximal pars distalis (PPD) of the pituitary gland and the testicular activity were examined. Intensely immunoreactive LH content was noticed in the PPD of the pituitary gland in the initial controls, controls on days 6 and 12, and fasting fish on day 6, whereas the LH immunoreactivity was moderate or weak in fasting fish on day 12. In addition, although the mean gonadosomatic and hepatosomatic indices among different experimental groups did not show any statistically significant difference, the mean numbers of spermatogonia, spermatocytes, and spermatids were significantly lower in food-deprived fish on days 6 or 12 compared to those of controls. The inhibition of the spermatogenesis was accompanied by the presence of abundant spermatozoa in the lumen of seminiferous tubules of the testis in food-deprived fish, whereas the occurrence of spermatozoa was relatively infrequent in initial controls and controls. Furthermore, refeeding to food-deprived fish on day 6 onwards resulted in occurrence of few intensely stained LH secreting cells and significantly higher numbers of spermatocytes and spermatids concomitant with sparse spermatozoa in majority of tubules compared to those of food-deprived fish. These results suggest that prolonged exposure to food-deprivation causes suppression of the LH secretory activity in the pituitary gland and disruption in the spermatogenesis in O. mossambicus.

     

Assessment of pollutant loads discharged from aquaculture ponds around Taihu Lake,China

China is the world's largest producer of aquatic animals, and the Taihu Lake area is one of the most important contributors within China. To obtain the basic information needed to minimize environmental impacts of aquaculture, the water quality and volume of effluents from 48 ponds used for raising crab, shrimp, river prawn, black carp, grass carp and turtles near Taihu Lake were monitored, and their pollutant loads were estimated. Effluent volumes ranged from 12.7 ± 1.7 (crab) to 50.9 ± 15.8 (turtle) thousand tons ha^?1 year^?1. The concentration of pollutants in the effluents often exceeded acceptable limits for Taihu Lake. Crab ponds produced the lowest gross loads of total nitrogen, total phosphorus, chemical oxygen demand and total suspended solids, whereas turtle ponds produced the highest. The net loads of monitored pollutants comprised only 4–53% of the gross loads in crab ponds, but > 50% in other species ponds. Results indicate that the pollutant loads discharged from aquaculture ponds around Taihu Lake are mild, but precautions are still needed to treat the wastewater. Connecting the ponds in series with crab ponds downstream is a feasible way to decrease pollutant loads.     

Variations in body condition of green turtles (Chelonia mydas) in two nearby foraging grounds indicate their sensitivity to foraging habitats

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The timing of puberty in cultured female yellowtail flounder, Limanda ferruginea (Storer): Oogenesis and sex steroid production in vivo and in vitro

This study examines puberty in female yellowtail flounder, correlating macroscopic, histological and endocrine parameters at the gonadal level. Short-term ovarian tissue incubations were used to study estradiol-17β production in relation to oogenic stage. Examining 2 year classes of young flounder demonstrated that cultured females retain phenotypic plasticity in reproductive age with pubertal onset occurring in one-year, two-year and three-year-olds. Immature ovaries were steroidogenic and capable of responding to gonadotropic stimulation. Endocrine puberty in females was detected by a peak in estradiol-17β production during the cortical alveolar oocyte stage prior to any ovarian evidence of vitellogenesis. Puberty, once initiated, proceeded to ovulation within 8 to 12 months; vitellogenic oocyte development followed the group synchronous pattern. Estradiol-17β was clearly the dominant of the two measured plasma hormones during pubertal onset and throughout vitellogenesis. Plasma testosterone was consistently detectable at low levels by mid-to late-vitellogenesis. Ovaries showed the highest sensitivity to gonadotropic stimulation in vitro during late-vitellogenesis. Variable plasma levels in both estradiol-17β and testosterone occurred in preovulatory and ovulating females during the captive spawning period. Together the results show that yellowtail flounder can mature at a young age and small size when culture conditions permit. In addition, the early sensitivity to gonadotropin by the immature ovaries may be an important physiological determinant for the timing of puberty in this species.     

Changes in Serum Steroid Hormones and Vitellogenin Levels in Cultured Female European Eels Anguilla anguilla during Artificially Induced Ovarian Development

Changes in serum concentrations of estradiol-17β, testosterone, 17α,20βdihydroxy-4-pregnen-3-one, and vitellogenin were investigated during ovarian development induced by injection of a salmon pituitary extract in cultured European eel Anguilla anguilla . Vitellogenesis was induced with a weekly dose of 50 mg pituitary extract/kg body weight. In eels receiving that dose, gonadsomatic indices ranged from 20–43% after the 10th–11th weekly injection. Body weights were relatively stable during vitellogenesis, but increased dramatically during final maturation. Serum estradiol-17β levels increased slightly during vitellogenesis and peaked at an average of 6.95 ng/mL at final maturation. The profile of serum vitellogenin followed that of estradiol-17β which increased markedly from an average of 0.36 to 20.72 mg/mL. Control levels of vitellogenin were undetectable throughout the study. Average serum levels of testosterone increased to a peak of 17.74 ng/mL in the early stage of vitellogenesis, followed by a sharp drop to initial levels (3.86 ng/mL) in the late stage of vitellogenesis, and then increased again to an average of 8.84 ng/mL at the final maturation stage. Serum 17α,20β-dihydroxy-4-pregnen-3-one was not detected (<50 pg/mL) throughout the experiment. Profiles of serum estradiol-17β, testosterone, and vitellogenin observed during ovarian development appear different from those found in salmonids and other teleosts. This study indicates, however, that cultured European eels are a useful model for study of gonadal maturation in the eel.