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1.
探究浮游细菌群落结构以及微生物与环境因子的相关性,可为湖泊环境评价和生态治理提供理论依据。选取湖北境内的梁子湖和后官湖,于2018年4月分别设置10个和5个采样点,进行浮游细菌与水体理化指标采样调查;通过16S rRNA基因高通量测序,分析比较浮游细菌群落结构及其多样性的差异,并通过冗余分析(RDA)探讨环境因子与浮游细菌群落结构的关系。结果表明,梁子湖和后官湖均有较高的浮游细菌群落多样性,其Shannon指数分别为3.974~4.743和3.924~4.500;梁子湖与后官湖的浮游细菌群落结构有所差异,梁子湖菌群隶属于放线菌门(Actinomycetes)、变形菌门(Proteobacteria)、拟杆菌门(Bacteroides)、蓝细菌门(Cyanobacteria)、疣微菌门(Verrucomicrobia)、绿菌门(Chlorobi)、绿弯菌门(Chloroflexi)、装甲菌门(Armatimonadetes)、厚壁菌门(Firmicutes)和硝化螺旋菌门(Nitrospirae);后官湖菌群隶属于放线菌门、蓝细菌门、变形菌门、拟杆菌门、疣微菌门、芽单胞菌门(Gemmatimonadetes)、绿弯菌门、绿菌门、浮霉菌门(Planctomycetes)、装甲菌门和螺旋体菌门(Saccharibacteria);其中,梁子湖的优势菌群为放线菌门(20.09%~43.23%)和变形菌门(21.35%~35.28%),而后官湖的优势菌群为放线菌门(20.70%~42.69%)和蓝细菌门(14.40%~45.77%)。RDA分析表明,总氮(TN)、pH、总磷(TP)是影响微生物群落结构的主要环境因子。  相似文献   

2.
研究密云水库入库河流水体中总细菌和反硝化菌的群落组成与差异性,为水库的安全管理与水质保障提供基础数据和科学依据。选择对密云水库水质影响最大的5条入库河流（潮河、白河、清水河、对家河和白马关河）,对水体中的总细菌和氮循环功能微生物反硝化菌进行了聚合酶链式反应（PCR）扩增与高通量测序分析。5条入库河流中全细菌主要隶属于6个门,而以Proteobacteria（变形菌门）为优势种群;反硝化菌在门水平的分布则相对简单,主要以Proteobacteria和少量Deferribacteres（脱铁杆菌门）构成。不同入库河流全细菌的群落结构具有空间差异,其中水文特征较为接近的白河和潮河全细菌群落结构具有较高相似性,与其他3条入库河流群落差别较大;水体中全细菌的Shannon多样性和Chao1丰富度均表现出较高水平。氮磷污染较重的对家河和潮河反硝化菌群落结构比较类似,其他3条入库河流之间则相对分散;对家河全细菌和反硝化菌的多样性和丰富度表现出较低水平。清水河水体中的全细菌和反硝化菌群落结构都较少受到已分析的环境因子影响,可能与该河道的人工改造有关。河流水体中全细菌以及关键功能微生物群落特征受到河流的水文、形态和理化指标的综合影响,可以作为水体环境与生态状况的重要指示项目,在今后的水库水环境保护与管理中应予以重视。  相似文献   

3.
采用基于16S rDNA的PCR-DGGE(变性梯度凝胶电泳)技术,比较分析了添加尼龙筛绢网基质对凡纳滨对虾(Litopenaeus vannamei)精养系统中水体细菌群落结构演替的影响。结果表明:1)基质组水体菌群结构丰富度稍低于对照组;2)基质组水体菌群结构相似性始终高于对照组;随着时间的推移,基质组的相似性系数不断升高,而对照组出现了先升高后下降的波动;3)对照组水体养殖前期优势菌主要为变形菌门和未培养细菌,在养殖后期则以厚壁菌门芽孢杆菌属(Bacillus spp.)细菌为主,基质组水体菌群则在整个养殖周期中均以厚壁菌门芽孢杆菌属细菌和未培养细菌为主。该研究结果可为进一步阐明人工基质养殖系统中微生物的生态调控功能和作用机制提供参考。  相似文献   

4.
微生物群落在水产养殖环境中起着重要作用,深入了解微生物群落组成及其构建机制对了解池塘生态功能具有重要意义。本研究通过高通量测序技术研究斑点叉尾鮰（）养殖池塘底泥中细菌群落机构特征,并分析了细菌群落的主要影响因素。结果显示,斑点叉尾鮰养殖池塘底泥细菌群落结构呈现出季节性变化,冬春季样品相似性较高。斑点叉尾鮰养殖池塘底泥优势菌群主要为变形菌门（Proteobacteria）、绿弯菌门（Chloroflexi）、拟杆菌门（Bacteroidetes）、厚壁菌门（Firmicutes）和酸杆菌门（Acidobacteria）,与池塘水体细菌群落间有明显的差别。线性判别分析显示,冬、春和秋季的特异性优势菌群较为丰富,冬季和春季分布较为集中,分别集中于浮霉菌、拟杆菌门、绿弯菌门和厚壁菌门、拟杆菌门,秋季特异性优势菌群分布特别分散,而夏季优势细菌类群最少,只有绿弯菌门厌氧绳菌属1个属具有显著优势。环境因子中,透明度和总溶解性悬浮物与斑点叉尾鮰养殖池塘底泥细菌群落结构有显著相关（<0.05）,对细菌群落结构的影响也最大。本研究旨为斑点叉尾鮰池塘微生物群落的变化和调控提供借鉴。  相似文献   

5.
光合细菌对水产养殖环境细菌群落结构的影响   总被引：1，自引：0，他引：1  
为了解光合细菌(Photosynthetic bacteria)在水产养殖应用中的作用机制,采用PCR-DGGE技术研究不同浓度光合细菌对养殖水体和底泥两个微环境细菌群落的影响。结果显示:水样菌群和底泥菌群有显著差异,各聚为一簇,水样菌群多样性比底泥丰富且波动性更大,泥样菌群则相对稳定,受外源菌群影响较小;添加光合细菌可显著增加水体菌群多样性,促使SAR11族未培养α-变形菌等固有菌群数量增加,从而影响水样菌群结构;同一阶段不同处理水样菌群多聚在一起,显示出较高结构相似性,不同处理并未造成组间菌群结构明显差异;光合细菌投加12 d后出现浓度减少。鉴定分析发现水样中46个菌群归属21个属,底泥11个菌群归属6个属,其中水样和底泥共同含有3个属,水样和底泥菌群主要隶属于蓝细菌门(Cyanobacteria)、变形菌门(Proteobacteria)、拟杆菌纲(Bacteroidetes)和绿弯菌门(Chloroflexi)。  相似文献   

6.
2018年11月对福建罗源湾5个特征站位表层海水进行样品采集,用宏基因组测序分析技术对样品中的细菌群落结构和多样性进行研究分析。样品的OTU数目和α-多样性分析结果表明,5个站位菌群数目从大到小排列为污水排放口生活密集区湾内远离污染地区出海口火电站排污口。在海湾内门水平物种丰度图中,5个优势门分别是变形菌门(Proteobacteria)、拟杆菌门(Bacteroides)、放线菌门(Actinobacteria)、蓝细菌(Cyanobacteria)和厚壁菌门(Firmicutes)。对照5个优势门的菌类进行环境因子相关性分析,显示pH和无机氮含量是影响罗源湾海湾细菌群落分布及多样性的主要环境因子。  相似文献   

7.
为了解白洋淀水域细菌多样性,于夏季采集水样进行水质和微生物群落结构分析。水质分析显示,白洋淀平均酸碱值(pH)为7.95,溶解氧(DO)为16.67 mg/L,属于偏碱性湖泊且含氧量丰富。通过Illumina NovaSeq6000高通量测序分析微生物群落结构表明:白洋淀不同采样点Chao1指数、Ace指数均较高,Shannon指数为7.151~8.443,Simpson指数为0.986~0.992,反映出白洋淀各采样点微生物群落多样性丰富、稳定性好,且细菌丰富度和多样性均以光淀(GD)最高。变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、蓝细菌门(Cyanobacteria)、拟杆菌门(Bacteroidetes)和放线菌门(Actinobacteria)是湖水的优势菌门,丰度之和能达到90%,且以变形菌门(Proteobacteria)为绝对优势菌门,丰度为44.15%~60.18%;在属水平上烧车淀(SCD)和枣林庄(ZLZ)以多核杆属(Polynucleobacter)为第一优势菌属,其余采样点优势菌属为unidentified_Cyanobacteria。CCA(canonial correspondence analysis)分析表明,pH和DO是影响白洋淀细菌群落结构的主要环境因子。  相似文献   

8.
结合基于细菌16S rRNA基因的T-RFLP技术与克隆测序技术,对象山港三疣梭子蟹、脊尾白虾混养模式下改良塘M1(塘底铺网四周铺砂)以及传统塘M2(土塘)水体不同季节细菌群落结构和多样性进行分析。结果显示,M1、M2养殖塘水体细菌群落主要由变形纲门(Proteobacteria)、拟杆菌门(Bacteroidetes)、放线菌门(Actinobacteria)、蓝藻门(Cyanobacteria)组成。养殖过程中,细菌群落结构随时间发生了显著变化,不同养殖塘水体细菌群落结构变化的方向不同。M1养殖塘水体由放线菌门主导的群落结构向蓝藻菌门以及变形菌门主导的群落结构发展,M2养殖水体由蓝藻菌门主导的向变形纲门主导的群落结构发展,说明养殖后期改良塘水体有利于蓝藻细菌的生长。无论是M1还是M2,拟杆菌门在8-9月含量最高,且养殖过程中在M2水体的含量始终高于M1。随着养殖时间的推移,M1养殖塘水体细菌群落由多样性指数高的稳定性结构向多样性指数低的不稳定性结构转变,而M2水体养殖后期仍保持较高的多样性指数。PCA分析结果显示,M1养殖塘水体细菌群落差异性大于M2,说明M2水体细菌群落对环境变化的抵御能力大于M1。相关性分析结果显示,不同养殖塘水体细菌群落分布受环境的影响效应不同。  相似文献   

9.
为了解湖泊生态系统中微生物群落的组成及其在生态系统中的作用和功能,实验基于高通量测序技术分析了鲥[鱼侯]淀芦苇、棕榈片、人工水草、网片四种不同基质附着细菌的群落结构组成,并采用PICRUSt对菌群功能进行了预测分析。结果显示:鲥[鱼侯]淀四种基质附着细菌群落组成丰富,共检测出38门91纲183目338科646属,优势菌门为变形菌门(Proteobacteria)、绿弯菌门(Chloroflexi)、蓝细菌门(Cyanobacteria)、拟杆菌门(Bacteroidetes)、疣微菌门(Verrucomicrobia)、放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)、浮霉菌门(planctomycetes)。通过α-多样性分析发现四种基质附着细菌多样性指数大小依次为芦苇基质>棕榈片基质>人工水草基质>网片基质,丰富度依次为棕榈片基质>芦苇基质>网片基质>人工水草基质。进行PCoA分析和聚类分析,发现棕榈片基质与芦苇基质的附着细菌群落较为相似,而网片基质与人工水草基质较为相似。采用PICRUSt进行菌群功能预测分析,表明主要的COG功能包括氨基酸运输和代谢、细胞壁/细胞膜/膜结构的生物合成、能量产生和转换、信号转导机制、无机离子转运与代谢、碳水化合物的运输和代谢等共涉及22个功能基因家族。以上结果表明,生态修复中天然芦苇的微生物多样性最优且自我净化能力最强,其次是棕榈片。  相似文献   

10.
为探明蟹公寓养殖模式下,高蛋白配合饲料替代杂鱼饲喂对拟穴青蟹菌群的影响,采用16S rRNA高通量测序技术,比较分析养殖过程中不同饵料组拟穴青蟹的肠道菌群结构。结果显示,各饵料组中优势菌群均为变形菌门、厚壁菌门、梭杆菌门和拟杆菌门,占操作分类单元总数85.84%以上。不同饵料组共有细菌操作分类单元(695个)占总数的18.92%,其序列数占总序列数的95.39%。主坐标分析显示不同饵料组肠道菌群的群落结构未产生显著分化。共现性网络分析显示,随养殖过程推进,微生物互作网络复杂度降低。功能预测分析显示,细菌次生代谢产物的生物合成、转运和分解代谢等功能主要在养殖前期出现显著性差异,而养殖后期饵料组间无显著性差异。试验结果表明,蟹公寓养殖过程中,不同饵料会对拟穴青蟹的肠道菌群造成影响。与杂鱼组相比,高蛋白配合饲料在维持肠道菌群多样性方面有一定优势,同时未显著影响肠道细菌群落结构和功能。  相似文献   

11.
The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.  相似文献   

12.
Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.  相似文献   

13.
In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.  相似文献   

14.
Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL?1 (1.25 ng well?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.  相似文献   

15.
Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).  相似文献   

16.
Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg?1 protein) than essential amino acids (425.82 ± 9.15 g kg?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.  相似文献   

17.
There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.  相似文献   

18.
This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.  相似文献   

19.
The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 103 to 3.76 × 105 cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 105 cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

20.
Plasma estradiol-17 (E2), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E2 and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E2 and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.  相似文献   

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