氮营养盐对浒苔、铁钉菜生长和叶绿素含量影响的研究

以大型海藻浒苔、铁钉菜为研究对象,设置2种不同的氮源NO3-N、NH4-N及浓度,在5种温度下,研究氮营养盐对浒苔、铁钉菜生长和叶绿素含量的影响。试验结果表明：在不同的温度下,氮源对2种藻类的生长都有影响,相对生长率比对照组的都有提高;随着氮源浓度的上升,浒苔、铁钉菜的生长率呈上升趋势;NH4-N更利于2种海藻的生长;浒苔的生长最适温度是20℃,铁钉菜的生长最适温度是30℃。氮源对2种海藻的叶绿素a、b的含量都有影响,叶绿素的含量相对对照组都有提高。     

温度对浒苔生长及不同氮源吸收特性的影响

为了评估浒苔(Ulva prolifera)对养殖废水的净化效果,本文研究了4个温度水平(22.5℃、25.5℃、28.5℃和31.5℃)和3种氮源(NH4Cl、NaNO2和NaNO3)下,浒苔对工厂化养殖水环境的适应能力及其净化效果。结果显示,96 h内4个温度处理组浒苔对总氨氮(TAN,包括NH4+-N和NH3)的平均吸收速率分别为14.65、14.88、14.48和13.53 μmol/(g?h),144 h内温度各处理组对亚硝态氮(NO2–-N)的平均吸收速率分别为11.28、10.48、9.11和8.38 μmol/(g?h),144 h内各温度处理组对硝态氮(NO3–-N)的平均吸收速率分别为9.41、8.62、8.80和7.35 μmol/(g?h);温度对浒苔的生长速率有极显著的影响(P<0.01),而氮源对浒苔的生长速率有显著影响(P<0.05);在相同氮源条件下,浒苔的生长速率随着温度的升高而逐渐降低;在相同温度条件下,氮源为氨氮(NH4+-N)时,浒苔的生长速率大于氮源为NO2–-N和NO3–-N的生长速率;温度和氮源对浒苔叶绿素a的含量影响不显著(P>0.05),氮源为NH4+-N和NO2–-N时,随着温度的升高,浒苔中叶绿素a的含量均有升高的趋势,而氮源为NO3–-N时,浒苔中叶绿素a的含量呈先降低再升高的趋势;温度和氮源对浒苔中类胡萝卜素的含量均有极显著影响(P<0.01)。随着温度的升高,各处理组浒苔中类胡萝卜素的含量均呈升高的趋势,其中,在28.5℃和31.5℃条件下,NO3–-N处理组浒苔类胡萝卜素的含量明显高于其他各处理组(P<0.05)。研究表明,温度在22.5℃~31.5℃范围内,浒苔可以有效吸收TAN、NO2–-N和NO3–-N等对虾工厂化养殖废水中的营养盐,浒苔对NH4+-N的吸收速率最大,但随着水温的升高,浒苔对NH4+-N、NO2–-N和NO3–-N的吸收速率均呈降低的趋势。     

镉污染对肠浒苔毒性作用研究

以肠浒苔中Chl_a含量、SOD活性、POD活性、CAT活性及可溶性蛋白含量等为指标,研究分析了不同浓度Cd2 对肠浒苔的胁迫作用。结果表明,较低浓度Cd2 对肠浒苔5项指标参数值均较对照组有一定的提高,随着Cd2 浓度的增加,5项指标参数值均下降,其中,浓度>10μmol/L时,CAT、POD活性逐渐下降;>15μmol/L时,Chl_a含量、SOD活性、可溶性蛋白含量下降。高浓度的Cd2 对肠浒苔具有明显的胁迫作用。     

江苏滨海县海域漂浮浒苔光合生理特性及其固碳潜力评估

测定了江苏滨海县海域漂浮浒苔(Ulva prolifera)的光合生理特性(叶绿素荧光参数、叶绿素含量、Rubisco活性、光合速率)和组织含碳量,并分析了浒苔暴发海区水体溶解性无机碳(dissolved inorganic carbon,DIC)浓度及pH值变化特征。结果表明:1)浒苔漂到滨海海域时藻体状态良好,藻体Fv/Fm达到0.67,Yield为0.57,总光合速率为66.99μmol(C)·g-1(FW)·h-1,叶绿素a和b的含量分别为0.91 mg·g-1和0.65mg·g-1,Rubisco活性达到11.39μmol(CO2)·g-1(FW)·min-1;2)覆盖区域不同位点海水无机碳体系各参数均出现不同程度的变化,从浒苔覆盖区边缘到中心,海水中DIC和HCO3-浓度逐步降低(P0.05),而海水pH值却逐渐升高(P0.05)。3)2008~2013连续6年暴发的绿潮藻生物量累计约达9 832.8×104t湿重,可固定CO2量达1 843.67×104t,说明浒苔对DIC的吸收能力较强,能促进海水无机碳体系循环,提高海水pH值,能一定程度上增加海洋碳汇强度。     

活性磷对浒苔生长和叶绿素含量影响的初步研究

该试验以大型海藻浒苔(Enterpmorpha prolifera)为研究对象,设置5个活性磷浓度梯度,研究活性磷对浒苔生长和叶绿素含量的影响.试验结果表明:添加活性磷对浒苔的生长有促进作用,而且添加磷的浓度不是越高越好,有个最适值(200 μmol/L),在此浓度下浒苔的生长率最高为13.13%,超过这个值反而对浒苔...     

变温对孔石莼生长和生化组成的影响

在光照培养箱中研究了变温(23±3)℃、(26±3)℃、(29±3)℃及相应的恒温对照23、26、29℃共6个温度处理对孔石莼生长、叶绿素含量、可溶性糖和蛋白质含量的影响。试验结果表明,与相应的恒温相比,变温对孔石莼的生长有促进作用,且随变温持续时间发生变化。(26±3)℃变温的促生长作用最强,其次为(23±3)℃、(29±3)℃。变温处理下孔石莼的叶绿素a、b含量降低,蛋白质含量减少。可溶性糖含量除在(26±3)℃变温处理下略有升高,其余变温处理下降低。变温虽然对孔石莼的生长有不同程度的促进作用,但不利于其叶绿素a、b合成及可溶性糖积累和蛋白质合成。这可能是藻类为适应环境因子变化而做出的积极生理调节。     

浒苔对有机高分子絮凝剂助凝作用的研究

为测试浒苔(Enteromorpha prolifera)对于有机高分子絮凝剂阴离子聚丙烯酰胺AP120的助凝效果,通过絮凝试验比较了浒苔投加量对于泥浆沉降比、pH值的影响,以及浒苔不同投加量情况下絮凝剂AP120投加量与浊度去除率的关系。结果表明,随浒苔投加量的增加,泥浆同一时间的沉降比呈现先降低后增大的趋势,浒苔投加量为1.0 g/L时较2.0 g/L、3.0 g/L同一时间泥浆沉降比低。泥浆的pH值随着浒苔投加量的增加而降低,当浒苔投加量为2.0 g/L时,泥浆液的pH值近似于7.0。浒苔作为AP120的助凝剂对提高泥浆絮凝后的浊度去除率有作用,浒苔投加量为2.0 g/L对AP120的助凝效果较好,AP120投加量为5.0 mg/L时,浊度去除率达到97.8%;浊度去除率达到95%时,絮凝剂AP120投加量可减少40%。     

条浒苔蛋白质的纤维素酶辅助提取及其性质

以条浒苔为研究对象,以蛋白质提取率为指标,通过单因素试验确定提取条件,后采用均匀设计确定纤维素酶辅助提取工艺条件。结果表明,条浒苔蛋白质的提取条件为pH 11.0,温度60℃,时间5h;纤维素酶辅助提取条件为料液比1∶50,温度30℃,pH 5.5,时间5.5h,加酶量5.0%,纤维素酶处理后再经水提取5h,在此条件下蛋白质的提取率为30.22%~35.74%。为浒苔深加工及资源化利用,测定浒苔蛋白质的功能特性,结果表明,条浒苔蛋白质的等电点pI=3.0,在pH 7时起泡性最好,起泡性随着蛋白质溶液的浓度增加而增强,泡沫稳定性在pH 3和质量浓度2mg/ml时最好,乳化性在4mg/ml时最好,乳化稳定性在2mg/ml时最好,条浒苔蛋白质的吸油性为131.6%,60℃时溶解性最大。     

浒苔对海水中重金属的富集研究及食用安全风险评估

研究了浒苔（Enteromorpha prolifera）分别在镉（Cd2＋,浓度分别为5、20、80μg/L）和铅（Pb2＋,浓度分别为5、20、80μg/L）及对照组的海水中培养时,2种重金属在其体内的积累规律。结果表明,浒苔对Cd和Pb具有较强的富集能力,对Cd的富集倍数范围为558～1882倍,对Pb的富集倍数范围为6295～11080倍。本研究并对富集Pb和Cd后浒苔的食用安全进行风险评估。     

铅离子对塔胞藻的生物学效应分析

以塔胞藻为试验材料．用不同浓度的含有Pb(NO3)2的培养液对塔胞藻进行多轮培养，随后分析了处理后代的遗传学效应。结果发现，随着铅离子浓度的升高，细胞的生长繁殖和体积在第1、2轮(9天为1轮)培养中均明显降低．而在第3轮培养时．藻细胞的繁殖和体积接近常态。而对处理后细胞内含物含量的分析表明．随着培养液中铅离子浓度增高．藻体细胞内的蛋白质、叶绿素等含量均明显下降．但对可溶性糖、核酸的含量影响不大。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

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.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

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.     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

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.     

Growth hormone (GH) and reproduction: a review

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

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.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

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).     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

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.     

Cardiac,ventilatory and metabolic responses of two ecologically dissimilar species of fish to waterborne cyanide

Changes in heart rate, ventilatory activity and oxygen consumption were determined in trout (Salmo gairdneri) and brown bullhead catfish (Ictalurus nebulosus) during exposure to a steadily increasing concentration of waterborne cyanide selected to produce death in 8–9 hours for each species. The lethal cyanide concentration for the bullheads was an order of magnitude higher than for trout. Trout developed an immediate and gradually increasing bradycardia throughout the exposure period. Cyanide produced tachycardia in the bullhead followed by a gradual onset of bradycardia as the concentration of cyanide was raised. Pericardial injection of atropine (a muscarinic cholinergic antagonist) indicated that bradycardia in the trout was due initially to increased vagal tone but later due to the direct effect of cyanide on the heart. Hyperventilation in the trout persisted throughout the exposure period, although the rate and amplitude fluctuated and was variable between individual fish. During the last hour of exposure (highest cyanide concentration), ventilation was characterized by rapid, shallow breaths followed by a sudden respiratory arrest. The bullheads exhibited hyperventilation during the first 3 hours of exposure followed by a gradual, linear drop in ventilation rate and amplitude until death occurred. Cardiac and ventilatory responses in both species were attributed to stimulation of central and peripheral chemoreceptors by cyanide. Evidence is presented which suggests the initial response in the bullheads was due, at least in part, to gustatory stimulation by the cyanide. Oxygen consumption of the trout remained above pre-exposure levels for the majority of the test period. Oxygen consumption in the bullhead paralleled the changes in heart and ventilatory rates. Whole-body lactate levels of fingerlings of both species during cyanide exposure were measured to estimate the extent of anaerobiosis. Whole-body lactate levels were much greater in the bullheads than the trout, indicating a higher capacity for anaerobiosis, possibly due to a greater fuel supply. Overall, the trout responded to cyanide in a manner similar to that produced by environmental hypoxia whereas the bullheads experienced a gustatory stimulus which masked the hypoxia-like response.     

An overview of stress physiology of fish transport: changes in water quality as a function of transport duration

This study brings an integrated analysis about the relationship between water deterioration and its physiological consequences in live fish transport. The analysis was focused on the transport water and its deterioration, and physiological challenges imposed on the fish. Usual commercial handling procedures employed to mitigate fish stress during transport were discussed. Future topics of research for the establishment of safer fish transport protocols were proposed. Transport was classified into short (≤8 h) or long transport (>8 h). The main issue in short transports should be the prevention of water pH reduction, while in long transports it is the increase in ammonia. Plasma cortisol is the most employed marker for stress and is acutely elevated upon short episodes of transport, but remains elevated even in long‐transport events. Plasma glucose is perhaps a better marker for handling stress. Plasma lactate, pH, osmolality CO₂ and ions should be more often evaluated. Plasma Na⁺ and Cl^‐ are very useful markers of acidosis, due to their respective exchange for H⁺ and , for acid–base regulation. The establishment of species‐specific transport protocols should be preceded by such combined analyses of water and physiological parameters.