利用mini-Tn10转座子文库筛选鳗弧菌M3表型发生变化的基因

为了寻找影响鳗弧菌(Vibrio anguillarum)表型变化的基因,本研究使用转座子mini-Tn10 (pLOF/Kana)构建了鳗弧菌M3突变株文库,筛选影响表型变化的菌株及相关基因,证明这些表型变化的突变子与毒力存在一定的相关性。对M3突变文库的1152突变子进行筛选,获得泳动能力改变的突变子1个(编号为6G_1),酪蛋白酶活性发生改变的突变子3个(编号为5A_11、7B_12和7E_12),明胶酶活性发生改变的突变子1个(编号为7H_1),以及菌膜形成能力发生显著变化的突变子3个(编号为5E_2、6A_2和6E_12)。对转座子插入位点进一步分析显示,一个磷酸二酯酶相关基因突变引起泳动能力增强(P<0.05),leuD、rseB和thiQ突变引起酪蛋白酶活性显著减弱(P<0.05),potD突变引起明胶蛋白酶活性显著减弱(P<0.05),leuO、ilvH和grpB的突变引起菌膜形成能力明显减弱(P<0.05)。对这些表型变化的突变子进行毒力感染,发现野生型M3是6G_1突变子的半数致死剂量(Lethal dose 50%,LD50)的2.04倍,该突变子毒力相对增强。5A_11、7B_12和7E_12的突变子LD50分别为野生型M3的2.96、3.25和3.36倍。7H_1的LD50是野生型M3的1.25倍,5E_2、6A_2和6E_12的LD50分别为野生型M3的3.34、4.08和1.84倍,这些突变子毒力相对减弱。本研究结果为进一步阐明鳗弧菌的发病机制提供了理论基础。     

鲁氏耶尔森菌invF基因无痕缺失突变株的构建及生物学特性

鲁氏耶尔森菌是一种具有广泛致病性的条件致病肠杆菌。三型分泌系统(T3SS)是该菌的重要毒力系统,其中invF基因是T3SS功能表达的重要调控因子。为探讨invF和T3SS对Y.ruckeri致病作用的影响,本研究构建了Y.ruckeri SC09株invF基因的无痕缺失株,并对其生物学特性进行研究。通过融合PCR方法,将invF基因的上、下游片段A、C融合,构建同源臂AC;将获得的同源臂AC连接入自杀质粒pLP12,构建pLP12-invF同源重组载体;pLP12-invF电转化进入供体菌株大肠杆菌β2163,并利用接合转移方法转入受体菌株Y.ruckeri SC09,利用抗生素正向筛选和vmt反向筛选分别对插入突变株和缺失突变株进行筛选,并利用PCR技术和序列测定对Y.ruckeri invF缺失株进行鉴定;对突变株和野生株进行菌体菌落形态观察、生化特性鉴定和生长曲线测定。结果显示,融合PCR、AC片段经氯霉素抗性正向筛选和vmt反向筛选,PCR鉴定和测序鉴定后,成功获得了Y.ruckeri SC09 invF基因的无痕缺失突变株,突变株和野生株菌体菌落形态和生化特性基本一致,突变株菌落较野生株小,各个时期突变株的生长浓度较野生株低。研究表明,采用自杀质粒pLP12和大肠杆菌β2163接合转移系统,利用抗生素正向筛选和vmt反向筛选技术,在对其基本生物学特性无显著影响的情况下,可简捷高效地获得invF基因的无痕缺失突变株。     

中华绒螯蟹肌肉抑制素基因(MSTN)同义突变对基因转录和翻译效率的影响

为分析同义突变对基因转录和翻译的影响,实验应用定点突变、体外转录和过表达等技术对中华绒螯蟹肌肉抑制素基因(Es-MSTN)中发现的5个SNP同义突变位点即SNP1(C/T)、SNP2(C/T)、SNP3(C/T)、SNP4(A/G)和SNP5(T/G),及其对应的12种基因型组合(CG、TA、1T、2T、3T、4A、5T、1C、2C、3C、4G和5G)进行了转录和翻译水平的研究。结果显示,12种基因型在体外转录中存在转录效率差异,1C基因型的转录水平最高,而CG和TA基因型的转录水平最低,差异显著;且TA基因型转录水平显著高于CG基因型。对上述基因型在293T细胞中进行过表达研究发现,不同突变基因型在转染后的不同时间(24、36、48、60、72、84、96和108 h)的表达强度存在显著差异,且TA突变基因型的表达强度显著高于CG突变基因型。研究表明,5个同义突变位点对中华绒螯蟹Es-MSTN的转录和翻译具有重要影响,同义突变也可能具有较为重要的生物学意义。     

溶藻弧菌双组分调控系统KdpDE减毒活疫苗的构建及其免疫效果评价

为了研究溶藻弧菌双组分调控系统KdpDE减毒活疫苗对鱼体的免疫保护作用,本研究采用Overlap PCR和同源重组技术,构建了kdpD/kdpE（kdpDE）基因无标记基因框内敲除突变株。对野生株和缺失突变株的生物学特性及致病性进行了比较研究,发现kdpDE的缺失对溶藻弧菌的生长速率和胞外蛋白酶活性的影响不明显,但是突变株的泳动能力、生物被膜形成能力较野生株下降。斑马鱼致病性实验结果显示,突变株毒力下降78.5倍,表明减毒株构建成功,可以作为减毒活疫苗的候选菌株。突变株在鱼体内存活能力实验结果显示,注射免疫7 d后,鱼体内不能检测到该菌。以突变株ΔkdpDE为抗原,分别用注射和浸泡的方式免疫斑马鱼,免疫后第28天用溶藻弧菌和哈维氏弧菌攻毒,评估该减毒活疫苗及不同免疫方式对斑马鱼的保护效果。实验结果表明,免疫后的斑马鱼能够抵抗溶藻弧菌的感染,其中注射免疫组的免疫保护率达83.3%,浸泡免疫组次之（66.7%）;同时,该减毒活疫苗能刺激斑马鱼对哈维氏弧菌产生交叉保护效应,其中注射免疫组的免疫保护率为65.5%,浸泡免疫组为55.2%。以上结果表明,kdpDE基因敲除突变株可能是抵抗溶藻弧菌感染的有效的候选减毒活疫苗。     

鳗草根际溶磷微生物分离、筛选及其对鳗草生长的影响

为明确鳗草(Zosteramarina)根际溶磷微生物溶磷能力及其对鳗草生长的影响,采用选择性无磷培养基从鳗草根际土壤中分离获得4株具较高溶磷能力的菌株(P1、P2、P3和P4),从形态学、生理生化特征及16Sr DNA等方面对菌株进行了鉴定,探讨了菌株的最适培养条件,研究了其对鳗草植株存活、生长、生理及根际土壤酶活力的影响。结果表明,菌株P1～P4分别为芽孢杆菌(Bacillus altitudinis P1)、桑肠杆菌(Enterobacter mori P2)、大肠埃希氏菌(Escherichia coli P3)和Cobetia marina P4; 72 h菌株培养液中可溶性磷含量分别为116.98 mg/L、123.13 mg/L、130.21 mg/L和76.54 mg/L;最适培养温度分别为34.67℃、33.95℃、34.60℃和31.19℃;最适培养盐度分别为27.10、28.29、29.54和26.08;最适初始pH分别为8.26、7.92、8.17和8.21。鳗草室外盆栽实验证实,4个接菌处理组对鳗草植株的存活、生长生理及根际土壤酶活力等指标均有不同程度的提高或改善。其中菌株P2对鳗草生长的影响最为显著,单株新叶面积、地上及地下生产力最高,为(54.31±4.79)cm~2、(3.58±0.36)mg/(shoot·d)及(0.28±0.04) mg/(shoot·d),是对照组的2.77、2.91和1.75倍;叶片中叶绿素a、叶绿素b、总叶绿素和类胡萝卜素4种光合色素含量分别为31.35μg/cm~2、12.57μg/cm2、39.42μg/cm~2和6.21μg/cm~2,显著高于对照组(P0.05)。除菌株P4处理组外,其余各处理组的碱性磷酸酶活力均显著高于对照组(P0.05)。但脲酶含量与对照组无显著差异(P0.05)。综合分析认为,桑肠杆菌(Enterobacter mori P2)具备进一步研制溶磷微生物肥料的潜力,在海草床生态系统恢复中可能具有较高的应用价值。研究结果为深入探究高效溶磷菌株功能与代谢调控及其在鳗草植株人工促繁中的作用奠定了基础。     

不同栽培方式对鳗草实生苗建成和生理的影响

在15 ℃条件下，研究了3种栽培方式(水培促萌+萌中插植、水培促萌+萌后插植以及基质栽培)对鳗草(Zostera marina)种子萌发、实生苗建成与生长的影响，分析了鳗草实生苗的培育成本及其应对不同栽培方式的生理响应。结果显示，水培促萌+萌中插植、水培促萌+萌后插植的鳗草种子萌发率和实生苗建成率无显著差异(P>0.05)，平均达到54.8%和46.5%，分别是基质栽培处理组的1.3和1.6倍(P<0.05)。水培促萌+萌中插植、水培促萌+萌后插植的鳗草实生苗的各项生长指标亦无显著差异(P>0.05)，其平均值均显著高于基质栽培处理组(P<0.05)，特别是根生成速率平均达到基质促萌处理组的1.6倍。主成分分析显示，水培促萌+基质插植的鳗草实生苗生理状态较优，其中，总氮和可溶性糖含量的贡献度较大，贡献度平均分别达到16.6%和15.0%，是基质栽培处理组的1.2倍(P<0.05)。培育成本分析显示，水培促萌+萌后插植栽培方式的培育成本最低(3.6元/株)，是水培促萌+萌中插植栽培方式的81.9%。综合实生苗培育效果和培育成本，水培促萌+萌后插植的栽培方式是适宜的鳗草实生苗栽培方式，其主要通过提升实生苗非结构性碳水化合物的形成和提高光合色素含量，实现对实生苗建成与生长的促进作用。     

草鱼MSTN-1基因多态性及与早期生长性状和肌肉成分关联分析

为研究草鱼MSTN-1基因多态性及与早期生长性状和肌肉成分的相关性,本研究扩增出全长为3824 bp的草鱼MSTN-1基因,用长江选育草鱼群体对MSTN-1基因多态性进行筛选和验证。结果共发现3个多态性位点(Locus 1:C1799T,野生型EE/突变型EF;Locus2:C1842T,野生型HH/突变型HI;Locus 3:TGAAGCGCTGGTTCT/2585-,野生型BB/缺失型BD)。利用一般线性模型分析3个位点及其组合型(剔除个体数少于3的组合)与生长性状和肌肉成分的相关性,发现2个位点对幼鱼生长性状表型差异有显著影响,但3个位点对肌肉成分差异均无显著影响。多重比较发现,单倍型HI突变组的体长和体质量显著高于HH野生组,BD突变组的体长和体质量显著性低于BB野生组;多倍型中存在HI突变组合的体长、体质量均显著高于其他组,存在BD突变的组合在体长性状方面显著低于其他组。表明草鱼MSTN-1基因3个SNPs中,HI突变是对草鱼生长性状的有利突变,BD突变是不利突变,而EF突变无显著影响,可将MSTN-1基因作为分子标记辅助草鱼选育的候选基因。     

鳗弧菌L-18株的限铁条件和铁调节外膜蛋白的免疫效果研究

利用Western-blot技术，对鳗弧菌L-18株的OMPs和IROMPs的免疫反应性进行了分析，并通过免疫牙鲆比较二者免疫保护力的差异，以期从IROMPs方向探索开发鳗弧菌新型鱼用疫苗，并为研究其免疫原理提供重要的科学依据。结果表明，培养基中加入不同浓度的联铁剂，鳗弧菌L-18株的生长和铁载体的表达出现规律性变化，其中加入100~130μmol·L-1 2,2’-联吡啶为最适合限铁条件，此时铁载体的表达量最高且生长受抑制程度较小。在此条件下，菌株表达出74.3ku和77.4ku的IROMPs，其中77.4ku蛋白具有免疫反应性，为重要抗原。用全菌灭活疫苗、OMPs、IROMPs分别腹腔注射免疫牙鲆7周后攻毒， IROMPs疫苗的相对免疫保护力达到75.9%，远高于OMPs疫苗的51.8%。相对于OMPs，IROMPs的抗体效价显著提高，接近全菌疫苗组的水平，而血清杀菌活力没有显著变化。 关键词：鳗弧菌；铁调节外膜蛋白；牙鲆     

拟态弧菌OmpU蛋白的黏附功能及所介导的致病作用

为了探明拟态弧菌OmpU蛋白的黏附功能,利用同源重组技术敲除基因组中OmpU基因,并构建其互补株,再经组合PCR方法和序列测定,证实了OmpU基因的缺失和互补。对野生株、缺失株和互补株进行了遗传稳定性、生长特性、生化特性、细胞黏附性、致病性等方面比较研究。结果显示,缺失株具有遗传稳定性;在相同的培养条件下,与野生株相比,突变株的培养特性和生化特性没有明显变化,生长速率略减慢,对实验草鱼的毒力降低了4倍,对鲤上皮瘤细胞(EPC)的黏附能力显著降低,下降了66.6%,而互补株的黏附能力和毒力又得到恢复,与野生株无明显差异。研究首次确证了拟态弧菌OmpU蛋白具有黏附功能,OmpU蛋白通过黏附参与致病作用。     

悉生条件下3株嗜盐古菌对卤虫生长及其抗弧菌感染的影响

嗜盐古菌存在于高盐水体中,是高盐环境微生物种群的重要组成部分。本研究利用从日晒盐场结晶池卤水中分离得到的3株红色嗜盐古菌,分别命名为Haloarcula sp.HG-1、Haloferax sp.KN-4和Halorubrum sp.IT-5。采用悉生实验系统,探讨不同盐度(30、100和150)条件下3株古菌能否作为卤虫(Artemia)的唯一饵料,并比较其作为饵料对卤虫存活、生长和抗鳗弧菌(Vibrio anguillarum)感染能力的影响。结果表明,在盐度30的悉生系统中,投喂3株古菌组卤虫存活率和体长均保持较高水平;鳗弧菌攻毒条件下,卤虫存活率有所下降,其中投喂Haloferax sp.KN-4菌株组卤虫抗鳗弧菌感染能力最强。正常和攻毒条件下,在盐度100和盐度150悉生系统中分别投喂3株古菌,卤虫均保持较高存活率和体长,其中投喂Haloarcula sp.HG-1菌株组卤虫具有最高存活率和最长体长,但攻毒组卤虫存活率和生长普遍优于未攻毒组,这可能与高盐条件下V.anguillarum毒力下降有关。本研究利用"卤虫-古菌"悉生实验系统,证实了3株嗜盐古菌均可作为卤虫的唯一饵料,为卤虫提供营养;利用"卤虫-古菌-致病菌"攻毒实验系统,证实3株嗜盐古菌均可以增强卤虫抗鳗弧菌感染能力。本研究结果为研究古菌在高盐环境食物链中的作用提供了基础数据。     

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.     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

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.     

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.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

Effects of cadmium on the kinetics of calcium uptake in developing tilapia larvae, Oreochromis mossambicus

The toxic effects of Cd²⁺ on Ca²⁺ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l^-1 of Cd²⁺ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca²⁺ uptake within 4h resulting in a great increase in K_m values for Ca²⁺ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca²⁺ influx of larvae in solutions of 0.2 mM Ca²⁺ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd²⁺ than 0 day-old larvae. Although the Ca²⁺ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l^-1 Cd²⁺ solution, total body Ca²⁺ content was significantly reduced in 3 day-old larvae. Increased Ca²⁺ uptake efficiency ensures sufficient Ca²⁺ for normal growth. However, rapid increase in Ca²⁺ influx after hatching also leads to higher Cd²⁺ uptake. Exposure to Cd²⁺ will lead to a drop in body Ca²⁺ content resulting in retardation of larval growth. Therefore, we conclude that if Ca²⁺ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca²⁺ and will show signs of Cd²⁺ poisoning.     

Migratory dynamics of stream-spawning longnose gar (Lepisosteus osseus)

Abstract– Literature evidence suggests that lake-dwelling longnose gar (Lepisosteus osseus) enter tributary streams to spawn, Until the present study, the dynamics of this breeding migration had never been investigated quantitatively. During the summers of 1991 and 1992, longnose gar were captured as they entered Weaubleau Creek, Missouri, a tributary of Harry S. Truman Reservoir. The in-stream spawning migration began in early April and ended in late May, and was positively correlated with stream flow and water level, and negatively correlated with water temperature. In-stream residence times ranged from 15 to 94 days, with males exhibiting longer residence times than females. Once in-stream, longnose gar travelled as far as 10 km upstream and occupied certain pools at greater relative frequencies. Although the reason for this preferential utilization is not completely understood, it may relate to pool depth and riffle proximity. Longnose gar disperse from the spawning stream great distances, with gar captured in Weaubleau Creek being recaptured up to 48 km away. This information should provide fisheries biologists the means to consider the reproductive ecology of this species in their conservation and management decisions.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。