中国对虾（Penaeus chinensis）卵子孵化和无节幼体变态环境中锌离子…

本文研究了海水环境中锌对中国对虾卵孵化和无节幼体变态的影响，结果表明，可溶性锌对卵子孵化和无节幼体变态的作用只与游离离子活度有关，而不是与其总浓度有关，锌离子活度在１０＾－７．３０ｍｏｌ／Ｌ以下时，不影响卵子的孵化率，高于此浓度会显著（Ｐ〈０．０５）降低孵化率；在１０＾－５．００ｍｏｌ／Ｌ时卵子完全不能孵化。锌离子活度在１０＾－７．６０ｍｏｌ／Ｌ时，不影响无幼体的生长变态，高于此浓度时，明显（Ｐ〉     

重金属离子除去装置在中国对虾育苗生产中的应用

自行研制的高分子吸附剂装置，在两处中等规模的中国对虾育苗场进行了应用实验。结果表明，在其他条件一致的情况下，应用装置与使用自然海水育苗对比，卵子的孵化率平均提高１１．８％，无节幼体到蚤状幼体变态率平均提高１０．２％；应用装置与使用ＥＤＴＡ（２．０ｍｇ／Ｌ）比较，卵子的孵化率平均提高７．５％，无节幼体到蚤状幼体的变态率平均提高３．６％。     

金藻（Isochrysis galbana）培养液中铜锌离子的最佳活度↑（*）

本文研究了铜，锌离子在球等鞭金藻的培养液中最佳存在活度。采用了一种新的海水处理方法，除去海水中的重金属离子，同时，计算了培养液中铜，锌离子活度，结果表明，金藻培养液中，铜，锌离子的最佳活度为１０＾－１３．５７－１０＾－８．８０ｍｏｌ／Ｌ和０－１０＾－６．００ｍｏｌ／Ｌ；铜离子表现了对金藻生长繁殖的必需性，而锌离子未表现出对金藻生长繁殖的必需性；当铜，锌离子活度分别大于１０＾－８．８０和１０＾－６．     

镧-氨基酸络合物对中国对虾卵子孵化和无节幼体变态的影响

研究了镧－氨基酸络合物对中国对虾（Penaeus chinensis）胚胎发育和无节幼体生长的影响。实验结果表明，对胚胎发育期为单、二细胞的卵子，镧－脯氨酸、镧－苯丙氨酸的最佳浓度范围分别为（1．50－4．00）mg/L和（0．50－3．00）mg/L，对卵子的孵化率有明显的促进作用，较对照组分别提高21．0％－46．0％及23．0％－42．8％（P＜0．05）；对无节幼体的变态也有促进作用，镧－脯氨酸、镧－苯丙氨酸垢最浓度范围分别为（0．50－4．00）mg/L和（0．50－3．00）mg/L，变态率较对照组分别提高16．4％－27．5％及20．4％－26．7％（P＜0．05）。镧－氨基酸络合物对卵子孵化及无节幼体变态的促进效果好于元素镧，镧－苯丙氨酸又好于镧－脯氨酸。     

对虾养殖实验围隔中的固氮作用及其氮输入

１９９７年６～１０月,以乙炔还原法进行了不同放养模式下对虾养殖实验中生物固氮作用的测定。结果表明,各围隔中,对虾单养（Ｙ－４）和对虾＋海湾扇贝（Ｙ－５）的固氮作用较高,均值分别为２．６２μｇＮ／（Ｌ·ｈｒ）和２．６５μｇＮ／（Ｌ·ｈｒ）;对虾＋罗非鱼＋缢蛏（Ｔ－５）的最低,为１．５３μｇＮ／（Ｌ·ｈｒ）,对虾＋缢蛏（Ｙ－６）和对虾＋罗非鱼（Ｙ－７）的分别为２．３０μｇＮ／（Ｌ·ｈｒ）和１．８９μｇＮ／（Ｌ·ｈｒ）。各围隔中固氮速率较高与水体有效氮含量较低及有效氮磷比值不高有关。水层固氮蓝藻主要为蓝球藻（Ｃｈｒｏｃｏｃｕｓ）和念珠藻（Ｎｏｓｔｏｃ）。估算各围隔实验期间固氮作用输入分别为Ｙ－４∶１７．７２ｇ;Ｙ－５∶１９．６３ｇ;Ｙ－６∶９．０５ｇ;Ｙ－７∶１０．５９ｇ;Ｔ－５∶７．９９ｇ。     

镧对青虾卵子孵化的影响研究初报

本文研究了Ｌａ＾３＋对青虾（Ｍａｃｒｏｂｒａｃｈｉｕｍ ｎｉｐｐｏｎｅｎｓｅ）卵子孵化出蚤状幼体的影响,结果表明：Ｌａ＾３＋的最佳浓度范围为１．２～４．８ｍｇ／１,扣提高孵化率２２．８％～２７．７％,镧对青虾卵子孵化的促进作用是通过卵子对镧的吸收实现的。     

“四大家鱼”对暴发性鱼病的抗病力的种间差异↑（*）

嗜水气单胞菌所引起的暴发性鱼病，是近年来危害我国淡水养殖业的主要病害之一。本文报导草鱼、青鱼、鳙、鲢对该病的抗病力的差异及机理的研究结果。在菌液浓度为６．０×１０￣８ＣＦＵ／ｍｌ（１０°，１０￣（－１），１０￣（－２），１０￣（－３）四个稀释度），注射剂量为０．３ｍｌ／尾时，半数致死生（ＬＤ＿（５０））分别是草鱼１０￣（－０．４８），青鱼１０￣（１．２５），鳙１０￣（－１．３７），鲢１０￣（－２．１９），差异显著（Ｐ＜Ｐ＿（０．０５））。四种鱼的白细胞吞噬百分率存在极显著差异（Ｐ＜Ｐ＿（０．０１）），其中草鱼极显著地（Ｐ＜Ｐ＿（０．０１））强于其他三种鱼。四种鱼的补体替代途径（Ｃ＿３旁路）杀菌力１２小时测定结果的大小顺序是草鱼＞青鱼＞鳙＞鲢，差异显著（Ｐ＜Ｐ＿（０．０５））。草鱼的补体总量极显著地（Ｐ＜Ｐ＿（０．０１））低于鲢、鳙。四种鱼的红细胞Ｃ＿３ｂ受体花环率存在显著差异（Ｐ＜Ｐ＿（０．０５）），顺序为鳙＞鲢＞草鱼＞青鱼。“四大家鱼”对暴发性鱼病的抗病力的种间差异，不仅同它们的免疫力的大小有关，也同它们对特定病原的易感性的大小有关。     

三种鲤对暴发性鱼病抗病力的差异

本文报道三种鲤对嗜水气单胞菌引起暴发性鱼病的抗病力试验结果。当菌液浓度为６．０×１０￣８ＣＦＵ／ｍｌ，采用１０￣０、１０￣（－１）、１０￣（－２）、１０￣（－３）四个稀释度、０．３ｍｌ／尾注射剂量时，建鲤、野鲤和镜鲤的半数致死量（ＬＤ＿（５０））分别为１０￣（－１．３７５）、１０￣（－０．９７６）、１０￣（－０．５６２）。这三种鲤的半数致死量差异显著（Ｆ＞Ｆ＿（０．０５））。从四个方面研究了抗病机理：白细胞吞噬功能和补体替代途径（Ｃ＿３旁路）杀菌能力，镜鲤较强于野鲤和建鲤，但无显著差异（Ｆ＜Ｆ０．０５）；红细胞Ｃ＿（３ｂ）受体花环率和补体总量（单位／ｍｌ），是建鲤＞野鲤＞镜鲤，差异极显著（Ｆ＞Ｆ０．０１）。本研究结果还表明建鲤的红细胞Ｃ＿（３ｂ）受体花环率和补体总量稍高，但对暴发性鱼病病原（嗜水气单胞菌）较易感染。以上结果证明，不同品系鲤鱼对暴发性鱼病有种内特异性。     

双齿围沙蚕人工育苗生产性试验

介绍了双齿围沙蚕育苗生产的全过程。６￣７月份,利用对虾育苗室及其设备,采捕自然海域上浮的异沙蚕体,孵化密度５０￣１００万粒／ｍ＾３,经３５ｄ培养,幼体平均体长１．５（０．５￣３．０）ｃｍ,１３６ｍ＾２出苗量４５５万条,平均３２６２５条／ｍ＾２。三刚节幼虫至四刚节幼虫成活率７０％,四刚节幼虫至底栖成活率４９．４％,底栖后至出池成活率４７．９％。     

海水单胞藻培养液中微量元素的最佳浓度↑（*）

本文通过正交试验,研究确定了铜、锌、锰、钼、钴、镍为牟氏角毛藻（Ｃｈａｅｔｏｃｅｒｏｓｍｕｌｅｒｉ）和金藻（Ｉｓｏｃｈｒｙｓｉｓｇａｌｈａｎａ）培养的必需元素,并确定了最佳浓度,依次为（１～５）×１０－８、１０－９、（５～１０）×１０－８、（１～５）×１０－８、１０－７～１０－９、１０－９ｍｏｌ／Ｌ。它们应用于牟氏角毛藻和金藻的培养,可使细胞浓度和叶绿素浓度分别提高２０４％～４３２％和１９７％～２５６％。本文的研究结果较著名的Ｍ－ｆ／２配方增加了镍,并对其他的五种元素的浓度进行了修订。铜、钼、钴的浓度和Ｍ－ｆ／２配方基本相同;锰的浓度低约１个数量级;锌的浓度低约２个数量级。     

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.