Spatial variability in growth and reproduction of the Pacific oyster Crassostrea gigas (Thunberg, 1793) along the west European coast

The Pacific oyster Crassostrea gigas was introduced in Europe for commercial purposes in the mid 1960s. It was initially thought that low winter temperatures would restrain this species' reproduction and settlement; however, its present distribution in areas where no introduction has taken place suggests that natural invasion and expansion has occurred. Along the European coast, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Whether C. gigas will continue to further expand through northern waters will depend on its physiological performance. In this study, the performance of wild oyster populations has been studied in terms of growth and reproduction at three stations: La Rochelle (France; 46°N), Yerseke (Oosterschelde estuary, The Netherlands, 51°N), and Texel (Wadden Sea estuary, The Netherlands, 53°N). The French population had the lowest somatic-shell mass ratio and an increase in maximum shell length, somatic and gonadal mass was observed from France to the Netherlands. In addition, mean oocyte diameter decreased significantly from south to north. The combination of increasing gonadal mass and decreasing oocyte volume suggests an increasing reproductive output in terms of egg numbers from France to The Netherlands. Differences in temperature between locations will at least be partly responsible for the observed patterns; however, other environmental factors (such as food availability, predation pressure, sediment type and/or seston concentration) cannot be excluded. Since smaller eggs (oocytes) are thought to have a longer development time, the environmental conditions along the Dutch coast may result in increased larval dispersal and possibly in further population expansion.     

Growth and reproduction of the bivalve Spisula subtruncata (da Costa) in Dutch coastal waters

The bivalve Spisula subtruncata is usually abundant in shallow coastal waters along the Dutch coast. However, its biomass has been decreasing since 1995. In order to assess whether reproductive failure may be the cause of the observed decline over the last decades, the energy investment in reproduction of a population of S. subtruncata from central Dutch coastal waters was studied. The population studied consisted of individuals of up to four years old. Shell length reached maximum values of around 32 mm and individual total body, somatic and gonadal ash-free dry mass reached maximum values of about 278 mg AFDM, 252 mg AFDM and 76 mg AFDM, respectively. A clear seasonal cycle in somatic and gonadal mass was observed. Somatic and gonadal mass indices increased in early spring and reached maximum values during summer, followed by a decrease to minimum values at the beginning of the following year. Spawning was in June–July and settlement of spat seems to have occurred in July–August. Mean oocyte diameter was 57.43 ± 0.03 μm, corresponding to a volume of 98972 μm³. These results suggested that reproductive failure was not the cause of the current population decline. Most likely, unsuccessful settlement of spat and/or severe predation during the first months of life were responsible for the observed patterns.     

重金属Cu、Pb对泥鳅(Misgurnus anguillicaudatus)卵细胞凋亡及DNA损伤的SCGE试验

采用室内暴露试验方法,以单细胞凝胶电泳技术(SCGE)检测,研究了Cu、Pb不同浓度梯度与不同暴露时间联合染毒对泥鳅卵细胞DNA的损伤.结果表明,各Cu、Pb浓度组DNA平均迁移长度增加,与阴性对照组比较差异有显著性(P＜0.05).此外,随着Cu、Pb染毒剂量的增加,各试验组DNA的平均迁移长度逐渐增加,在试验浓度梯度范围内(Cu 0.01mg/L+Pb 0.05mg/L、Cu 0.10mg/L+Pb 0.50mg/L、Cu 0.25mg/L+Pb 0.75mg/L),存在较为显著的剂量-效应关系(P＜0.05),但未见明显的时间-效应关系(P＞0.05).Cu、Pb可引起泥鳅卵细胞凋亡和DNA损伤,卵细胞的不同损伤水平可望作为较为理想的水环境基因毒性指标.     

可口革囊星虫(Phascolosoma esculenta)卵黄合成期卵母细胞发育及卵黄发生与卵膜形成的超微结构

采用电镜技术观察研究了可口革囊星虫卵黄合成期卵母细胞发育及卵黄发生与卵膜形成的超微结构特征。结果表明,可口革囊星虫卵黄合成期卵母细胞发育经历了卵黄合成初期、卵黄旺盛合成期及生长成熟期三个阶段。卵母细胞卵黄发生途径主要由线粒体、内质网、高尔基体等细胞器演变成卵黄粒,以及吞饮作用形成卵黄粒。卵母细胞质膜外被有卵黄膜,由卵母细胞自体形成,且随生长而加厚;卵黄膜具通透性,外源营养物质能透过卵黄膜进入卵内。生长成熟的卵母细胞卵黄膜厚7—9μm,从内向外由纤维层、致密层、粒状突层及外膜构成,保护卵母细胞维持特定的形状。     

香鱼(Plecoglossus altivelis)排卵后卵内油球、酶活、丙二醛及受精率、孵化率的变化

以香鱼卵母细胞为研究对象,采用观察卵内油球、有关酶的活力、以及卵的受精率和孵化率等变化的方法,研究了香鱼卵母细胞长时效演化的相关机理,结果表明,随着香鱼卵在腹腔内保存时间的延长,卵内油球从0h的油球直径≤10μm,且均匀分布,逐渐融合增大,至108h增大到120μm,油球数仅有5—6个。同时,SOD、POD的活力及MDA含量均呈先升后降的变化趋势,最大峰值分别出现在60h、36h和24h。随着油球和酶活的变化,卵子质量逐渐下降,表现为受精率和孵化率的降低:排卵后24h、48h、72h、96h的受精率分别为94.37%、88.19%、50.20%、10.83%,孵化率分别为85.78%、68.14%、25.54%、0.53%。     

三疣梭子蟹(Portunus trituberculatus)卵子发生、激活与早期卵裂的细胞学观察

采用连续切片和光镜技术,对三疣梭子蟹卵子发生、激活和早期卵裂进行了细胞学观察.结果表明,在发育及再发育的卵巢中,三疣梭子蟹卵子发生主要经历了卵原细胞的增殖和初级卵母细胞的分化、生长、成熟这两个阶段.依据卵子发生过程中雌性生殖细胞形态的变化,这两个阶段又可细分为卵原细胞期、卵黄发生前卵母细胞期、小生长期、大生长期、近成熟卵母细胞期和成熟卵母细胞期等6期.成熟卵母细胞处于第一次减数分裂中期,这可作为卵子成熟的形态学标志.第一次减数分裂中期纺缍体长轴的旋转可以发生于卵巢中,与精子及海水的刺激无关.初级卵母细胞达到形态和生理上都成熟的时间窗口很窄.精子入卵引起卵子的激活和减数分裂的完成.23℃下离体培养时,第一和第二极体分别在卵产出后约40min和2h释放.雄原核的形成早于雌原核.雌、雄原核在卵产出后约5h通过联合形成合子核.卵产出后约6h,受精卵处于第一次核分裂后期,但卵裂沟直到卵产出后13h才能观察到,此时核已完成了2次分裂,形成合胞体胚胎.     

马粪海胆卵母细胞线粒体DNA和RNAs的分离

于１９８２年１２月－１９８４年５月，以青岛汇泉湾习见的马粪海胆为材料，运用０．５ｍｏｌ／Ｌ ＫＣｌ或０．５ｍｏｌ／Ｌ ＬｉＣｌ诱导法得到其卵母细胞；差速离心技术提取其线粒体；ＳＤＳ萃取到线体核酸；再以羟基磷灰石柱层析分离邮线粒体核酸各组分。结果表明，从所得各种分离产物测不出任何蛋白质，所以，应用上述各种方法和技术，能够有效地分离出海胆卵母细胞线粒体中的ＤＮＡ，ｒＲＮＡ，ｔＲＮＡ和多核苷酸。     

中国对虾卵母细胞发育的初步研究

于１９８９年１０月－１９９０年９月分别先后在昌邑县下营镇对虾育苗场和青岛黄岛盐业公司养殖场采集中国对虾，运用光学，电子显微镜及组化方法，研究中国对虾卵母细胞的形态发育及其内部结构分化。结果表明，中国对虾卵母细胞的发育可分为４个主要时相：Ⅰ．早期分化时相，Ⅱ滤泡初生期时相，Ⅲ卵黄大量生成时相，Ⅳ皮质棒生成时相。     

Sonophotocatalysis of endocrine-disrupting chemicals

Sonolysis and photolysis often exhibit synergistic effects in the degradation of organic molecules. An assay of fish oocyte maturation provides an appropriate experimental system to investigate the hormonal activities of chemical agents. Oocyte maturation in fish is triggered by maturation-inducing hormone (MIH), which acts on receptors on the oocyte surface. A synthetic estrogen, diethylstilbestrol (DES), possesses inducing activity of fish oocyte maturation, and a widely used biocide, pentachlorophenol (PCP), exhibits a potent inhibitory effect on fish oocyte maturation. In this study, the effects of the combined treatment by sonolysis with photolysis (sonophotocatalysis) to diminish the hormonal activity of DES and the maturation preventing activity of PCP was examined. By sonophotocatalysis, hormonal activity of DES was completely lost within 30min and the inhibiting activity of PCP was lost within 120min. These results demonstrated that sonophotocatalysis is effective for diminishing the endocrine-disrupting activity of chemical agents.     

The dynamics of postovulatory follicle degeneration and oocyte growth in Baltic sprat

Ovaries of Baltic sprat (Sprattus sprattus balticus S.) were analysed histologically to identify stages of postovulatory follicles (POF) and to assess the oocyte development pattern. Samples were taken every 3 h during a 24 h trawl survey conducted in the Bornholm Basin in April 2007. Gonad histology revealed spawning of sprat throughout the day which hampered the exact ageing of POFs by the postovulatory follicle method and therefore did not allow direct estimation of spawning frequency. However, it was possible to define four stages of POFs, according to their histological features. The occurrence of these POF stages (I to IV) corresponded clearly to the development of the leading oocyte cohort. Further, the oocyte recruitment pattern revealed that the spawning batch can be identified prior to hydration. The POF stages I and II were present almost exclusively in vitellogenic ovaries, POF III were found in ovaries in the germinal vesicle stage, and the most deteriorated POF stage IV was found in actively spawning fish with hydrated oocytes. Since POF were absent only in very few ovaries (5%), and in each ovary in general only one POF stage was present, the duration of POF degeneration approximately equals the average batch interval, i.e. the time lag between subsequent spawning events. The results of the present study will serve as basis for future studies on Baltic sprat oocyte recruitment and daily spawning fraction.