紫红笛鲷体内三种性腺激素的残留

采用放射免疫分析法测定了养殖紫红笛鲷与野生鲷肌肉中雌二醇、孕酮、睾酮3种性腺激素残留。结果表明,在养殖紫红笛鲷肌肉中均检出3种激素,养殖紫红笛鲷肌肉中3种性腺激素的残留量分别是野生紫红笛鲷的4．50倍、1．57倍、5．00倍;野生紫红笛鲷中的激素残留量较低,但仍能被检出,可能与环境激素有关。     

斜带髭鲷早期发育的形态观察

对笛鲷属(Lutjanus)的紫红笛鲷(Lutjanusargentimaculatus)、白星笛鲷(Lutjanusstellatus)、千年笛鲷(Lutjanussebae)、勒氏笛鲷(Lutjanusrussellii)、红鳍笛鲷(Lutjanuserythropterus)线粒体DNA16SrRNA基因片段进行了PCR扩增和测序,得到长度约418bp的序列。结合GenBank中斜带笛鲷(Lutjanusdecussatus)该区段的16SrRNA序列,用Clustal＿X排序软件进行16SrRNA序列的对位排列。通过Mega2.1软件对所得线粒体16SrRNA片段序列进行比较,共检测53个碱基存在变异,其中包括21个简约信息位点,并用"Pairwisedistance"计算了各属间的相对遗传距离,结果表明,其序列差异(转换 颠换)在0.027～0.083,其中勒氏笛鲷与斜带笛鲷的序列差异最小,红鳍笛鲷与勒氏笛鲷的序列差异最大。以高体四长棘鲷(Argyropsspinifer)为外类群,采用Mega2.1软件中的"Neighbore-Joining"法得到唯一1个分子系统树,系统树各分支的置信度由"Bootstrap"1000循环检验。结果表明,6种笛鲷鱼类聚成明显的3个分支,第1个分支,包括勒氏笛鲷、斜带笛鲷和白星笛鲷;第2个分支,包括紫红笛鲷;第3个分支,包括红鳍笛鲷和千年笛鲷。     

紫红笛鲷体内三种违禁激素残留水平的研究

本文采用放射免疫分析法检测了养殖紫红笛鲷与野生紫红笛鲷肌肉中雌二醇、孕酮、睾酮三种违禁性腺激素的残留水平.结果表明,在养殖紫红笛鲷与野生紫红笛鲷肌肉中均检出三种违禁激素,养殖紫红笛鲷肌肉中三种违禁性腺激素的残留量分别是野生紫红笛鲷的4.50、1.57、5.00倍;野生紫红笛鲷中的违禁激素残留水平较低,但仍能被检出,可能与海湾环境激素水平有关.     

6种笛鲷属鱼类线粒体16S rRNA基因片段的序列比较

对笛鲷属(Lutjanus)的紫红笛鲷(Lutjanus argentimaculatus)、白星笛鲷(Lutjanus stellatus)、千年笛鲷(Lutjanus sebae)、勒氏笛鲷(Lutjanus russellii)、红鳍笛鲷(Lutjanus erythropterus)线粒体DNA 16SrRNA基因片段进行了PCR扩增和测序，得到长度约418bp的序列。结合GenBank中斜带笛鲷(Lutjanus decussatus)该区段的16SrRNA序列，用(Clustal_X排序软件进行16SrRNA序列的对位排列。通过Mega2．1软件对所得线粒体16SrRNA片段序列进行比较，共检测53个碱基存在变异，其中包括21个简约信息位点，并用“PairWise distance”计算了各属间的相对遗传距离，结果表明，其序列差异(转换 颠换)在0．027～0．083，其中勒氏笛鲷与斜带笛鲷的序列差异最小，红鳍笛鲷与勒氏笛鲷的序列差异最大。以高体四长棘鲷(Argyrops spinifer)为外类群，采用Mega2．1软件中的“Neighbore-Joining‘’法得到唯一1个分子系统树，系统树各分支的置信度南“Bootstrap”1000循环检验。结果表明，6种笛鲷鱼类聚成明显的3个分支，第1个分支，包括勒氏笛鲷、斜带笛鲷和白星笛鲷；第2个分支，包括紫红笛鲷；第3个分支，包括红鳍笛鲷和千年笛鲷。     

内陆咸淡水主养紫红笛鲷创高效

紫红笛鲷属笛鲷科，别名银斑笛鲷、银纹笛鲷、红鲅、海鲤。分布于太平洋中西部、印度洋、我国南海及东海南部，主产于印度、西太平洋。上世纪70年代以来已开展养殖和育苗试验。紫红笛鲷体长一般15～35厘米，为体高的2．51～2．84倍，体紫红色，腹部银白色。该鱼属暖水性中下层鱼类，栖息于近海岸礁或泥沙底质、水深80米的海区     

紫红笛鲷与红鳍笛鲷5种同工酶的比较研究

采用聚丙烯酰胺垂直平板梯度凝胶电泳的方法,对紫红笛鲷和红鳍笛鲷8种组织中的5种同工酶(EST,LDH,MDH,ME,POD)进行比较研究,对所研究的5种同工酶在两种鱼的组织分布、位点表达及活性作了分析和总结。试验结果表明:两种鱼的ME、MDH同工酶谱非常相似,只在活性上略有差异;EST、LDH、POD等的酶谱表达带型和活性不同,这些酶可作为紫红笛鲷和红鳍笛鲷的遗传鉴定标记,能够将亲缘关系很近的这两种鱼区分开来,从而为形态分类学提供生化依据。     

杂交笛鲷人工繁育技术的初步研究

红鳍笛鲷(♀,40尾)×千年笛鲷(♂,45尾)杂交,得到受精卵2.2kg,浮卵率为78.57%,受精卵的孵化率为90.51%,共得到健康仔鱼349.2万尾;千年笛鲷(♀,30尾)×红鳍笛鲷(♂,28尾)的杂交,不成功。在水温27.5~33.5℃、盐度27.5~32.5、pH7.6~8.3、溶解氧4~6 mg/L条件下,杂交笛鲷仔鱼经过32 d的培育,用3个育苗池塘(面积共0.933 hm2)培育出平均全长36.8 mm的幼鱼44.4万尾,单位面积培育鱼种47.57万尾/hm2,育苗成活率为8.95%。     

4种笛鲷属鱼类随机扩增多态性DNA及遗传多样性研究

使用RAPD技术分析了红鳍笛鲷、紫红笛鲷、勒氏笛鲷和约氏笛鲷的种内遗传多样性、种间遗传多样性和种间亲缘关系。在120个随机引物中筛选出扩增效果好的引物36个,平均每个引物在每个个体上产生7．7个条带。种内遗传多样性研究结果显示：遗传距离(D)分别为0．2257,0．2228,0．2679和0．2247;遗传多样性指数(H)分别为0．1854,0．1904,0．2015和0．1865。说明目前湛江近海这4种笛鲷的遗传多样性比较丰富,它们的种质资源仍处于一个良好的水平。种间遗传多样性结果显示：勒氏笛鲷与约氏笛鲷遗传距离(Dpq)最小,亲缘关系最密切,勒氏笛鲷与红鳍笛鲷种间Dpq最大,亲缘关系最远。     

斜带髭鲷养殖技术

本介绍斜带髭鲷Hapalogenys nitens Richardson的分类、生态习性和养殖方法。斜带髭鲷最适生长水温22－28℃，最适盐度26－32‰；要求pH8.0-8.4；溶解氧含量4mg/L以上，养殖场所的选择在水质条件好，无污染的海区为宜，种苗放养密度约为35尾／m^3.     

真鲷和斜带髭鲷活鱼运输的适宜密度和水温

通过小水体试验和实船运输观察研究了真鲷(Pagrosomus major)和斜带髭鲷(Hapalogenys nitens)活鱼运输的密度和水温。结果表明,利用控温循环水系统,运输密度62.5~83.3 kg/m3,水温15~16℃条件下运输真鲷和斜带髭鲷活鱼是适宜的,运输过程中水质和溶氧的变化都在可允许范围之内,运输存活率可达到98%。     

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).     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

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.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

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.     

Nitrogenous waste excretion and accumulation of urea and ammonia inChalcalburnus tarichi (Cyprinidae), endemic to the extremely alkaline Lake Van (Eastern Turkey)

The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 – 19°C; pH 9.8; 153 mEq·I^–1 total alkalinity; 22 total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169moles·kg^–1 fish·h^–1, respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 – 35moles·g^–1·ml^–1) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min^–1·g^–1) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min^–1·g^–1) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated.