锌在鲫体内的积累特性

采用室内暴露试验法,研究不同质量浓度锌短期内在鲫鳃、肝胰脏和肌肉中的积累特性.试验结果表明,锌在鲫鳃、肝胰脏和肌肉中的积累量均随暴露时间延长而增加,但随时间变化锌的积累速率不同.鳃锌积累在0.05 mg/L锌溶液中呈线性关系,其他浓度均呈对数关系;不同质量浓度鲫肌肉锌积累量与暴露时间呈线形关系,暴露在0.05 mg/L锌溶液中,肌肉锌在10 d内积累速度较慢,10 d后积累速率大幅度提高,肝胰脏锌在0.05、0.1 mg/L锌溶液中积累量与暴露时间呈线性关系,其他浓度随时间呈对数关系.暴露在高于国家水质允许锌浓度水体中,肝胰脏可在短时间内快速积累锌.鲫各部位对锌的积累能力为肝胰脏>鳃>肌肉.     

铅在鲤鱼体内积累和排出的试验研究

本文讨论水中溶解铅在鲤鱼体积累和排出的过程。水中铅浓度为0.1ppm、1.0ppm和5.0ppm。积累程度随试验铅浓度和暴露铅时间增加而加强,浓缩系数则基本相反。当铅积累到一定程度时,则出现吸收—积累—排出的动态平衡,鱼体铅在清水中排出的速度随铅积累量的增加而缓慢。各组织铅积累量随着不同暴露时间会有不同的消长,最终各组织内铅积累依次为肝>肠>鳃>肌肉>骨骼;进入鱼体之铅能抑制胆碱酯酶活力和降低血红蛋白含量,说明神经系统和造血系统已遭损害。     

混合金属离子Pb、Zn和Cu的相互作用对Cd在鲫体内积累的影响

采用室内生态学方法研究混合重金属离子Pb、Zn和Cu的相互作用对Cd在鲫组织中积累的影响.结果表明,混合重金属离子相互作用对Cd在鲫组织中积累的影响与离子的种类、数量及组织类型有关.Cd的积累受单一重金属影响不显著,与Pb、Zn、Cu的混合作用关系密切.随重金属离子种类的增加,相互作用对积累的影响显著;Pb、Zn、Cu的混合降低了Cd在鳃中的积累量,增加了Cd在肝脏中的积累量,对Cd在肌肉中的积累无影响.Cd在鲫组织中的积累顺序为:肝胰脏>鳃>肌肉.     

铅在草鱼体内的富集及其对组织结构的影响

以草鱼(Ctenopharyngodon idellus)鱼种为受试对象,采用浸浴法在系列铅离子(Pb2+)质量浓度下暴露4 d,检测了草鱼鱼苗肝脏、鳃、肌肉、鳞片对Pb2+的累积作用及其对肝脏和鳃组织结构的影响。结果表明,草鱼鱼种各个器官对Pb2+的累积量随着浓度的升高和时间的延长而增多;草鱼的不同组织对Pb2+的累积量有较大的差异,24、48、72 h对铅累积作用由大到小为:鳃>内脏>鳞片>肌肉,96 h对铅累积作用由大到小为:内脏>鳃>鳞片>肌肉;铅暴露后的草鱼鱼苗肝细胞出现肿大,大小不一,核萎缩变形,并偏离中心,被挤至细胞边缘,细胞间隙明显增大,细胞排列混乱;鳃组织中鳃小片之间出现弯曲、融合现象,容易断裂,鳃小片的顶端充血,呈球状或棒状。暴露时间越长,铅对草鱼的肝脏和鳃组织结构损害程度越严重。     

铅在建鲤幼鱼组织中的积累与净化研究

采用半静态暴露染毒方式探讨了建鲤(Cyprinus carpio var.Jian)幼鱼肝胰脏、肠、鳃和肌肉中重金属铅的积累和净化特征,暴露水体含铅量为0.506μg/L。结果表明,不同部位中铅的积累量差异显著(P<0.05),积累量为肝胰脏>鳃>肠>肌肉。建鲤移入清水后,随着净化时间的延长,不同组织中铅的含量均逐渐降低,但变化趋势不同。肠中的铅被迅速净化;肝胰脏中铅的净化速度初期较快,之后变化缓慢,呈现波浪式起伏;鳃中的铅净化缓慢,肌肉中的铅含量下降缓慢,但在净化期其铅含量均低于国家标准。     

镉暴露对鲢幼鱼游泳行为影响的研究

为了探讨水体镉(Cd)污染对鱼类的生态毒理效应,在实验室条件下,测定了不同浓度Cd(0、0.36、0.73、1.09和1.46 mg/L)暴露对鲢(Hypophthalmichthys molitrix)幼鱼半致死浓度、组织(肝、鳃、肌肉)Cd累积量、相对临界游泳速度(Ucrit)、以及耗氧率(MO_2)的影响。结果显示:Cd暴露导致重金属在幼鱼组织中累积,与对照组比较,Cd在鳃和肌肉中累积量差异不显著;肝脏中累积量差异显著,暴露浓度为0.73 mg/L时肝脏中镉累积量最高。鲢幼鱼相对临界游泳速度随着Cd暴露增加显著降低,浓度为1.46 mg/L时Ucrit为对照组的69.75%。临界游泳速度与鳃和肌肉组织中镉累积量呈显著负相关,相关系数分别为-0.96(P=0.01)和-0.90(P=0.04)。Cd暴露导致鲢幼鱼耗氧代谢范围增加,暴露浓度为0.73 mg/L时耗氧代谢范围较对照组增加了19.32%。低浓度Cd暴露导致鳃和肌肉损伤,并引起鲢幼鱼游泳过程中耗氧代谢效率降低,有氧运动能力和游泳能力下降。     

铜在栉孔扇贝组织蓄积、分配、排放的研究

采用暴露实验方法,研究了海水中铜离子在栉孔扇贝(Chlamys farreri)内脏、肌肉、鳃组织内吸收、积累和排放规律。结果表明:铜浓度为0.05 mg/L时,各组织内铜蓄积量随暴露时间增加而增大,第13天均达吸收平衡,此时铜蓄积量(mg/kg干重)为:鳃79.65>内脏58.40>肌肉15.99;蓄积速率(mg/kg.d)为:鳃4.830>内脏4.800>肌肉1.000。将达到吸收平衡后的栉孔扇贝移入清洁海水中,排放结果表明:随排放时间增加,各组织铜离子蓄积量明显下降,第17天时各组织铜排出率为:鳃97.68%>内脏96.50%>肌肉73.60%;排出速率为(mg/kg.d)为:鳃3.820>内脏3.210>肌肉0.740。海水中铜浓度对铜蓄积量有明显影响,随着铜浓度升高,各组织内铜蓄积量明显上升,其中内脏团的蓄积量最大;表明栉孔扇贝的内脏团具有较高的蓄积重金属铜的能力。     

栉孔扇贝对海水中Pb积累排放规律研究

研究了海水中Pb在栉孔扇贝(Chlamysfarreri)内脏、肌肉、鳃组织内吸收、积累和排放规律及海水中不同浓度Pb对栉孔扇贝(Chlamysfarreri)内脏、肌肉、鳃组织蓄积量的影响。结果表明:Pb浓度为0.5mg/L时,各组织内Pb蓄积量随暴露时间增加而增大,第9天均达吸收平衡,此时Pb蓄积量(mg/kg干重)为鳃(1356)>内脏(226.6)>肌肉(52.14);蓄积速率(mg/kg·d-1)为鳃(178.3)>内脏(37.30)>肌肉(10.48)。将达到吸收平衡后的栉孔扇贝移入清洁海水中排放结果表明:随排放时间增加各组织铅蓄积量明显下降,第16天时各组织铅排出率为:鳃(96.69%)>内脏(92.09%)>肌肉(71.20)%;排出速率为(mg/kg·d-1):鳃(81.98)>内脏(10.09)>肌肉(3.001)。海水中Pb浓度对Pb蓄积量有明显影响,随着Pb浓度升高,各组织内Pb蓄积量明显上升,其中鳃的蓄积量最大,表明:双壳类软体动物的鳃具有较高的蓄积重金属的能力,并且海水中Pb浓度能提高Pb的生物有效性。     

氯化三丁基锡对黑鲷鳃和肝组织SOD、MDA和GPx的影响

观察和比较了黑鲷Sparus macrocephalus在不同浓度的氯化三丁基锡(tri-n-butyltin chloride,TBTCl)溶液中暴露后,其鳃和肝脏组织中超氧化物歧化酶(superoxide dismutase,SOD)活性、丙二醛(malondialdehyde,MDA)含量和谷胱甘肽过氧化物酶(glutathione peroxidase,GPx)活性的变化情况.结果表明,TBTCl对黑鲷鳃SOD活性有抑制作用,对肝脏SOD活性表现出促进作用;暴露TBTCl溶液中24 h后,黑鲷鳃和肝脏MDA含量均有升高,且随浓度变化与对照组比较有显著性差异(P<0.05),但暴露48 h后,2组织中MDA含量相对于对照组均降低.TBTCl对黑鲷鳃GPx活性的影响先是表现出显著性抑制,之后随时间延长呈显著的促进效应,肝脏则呈现随浓度增加GPx活性被显著性地促进的趋势.黑鲷体内鳃和肝脏组织中抗氧化酶系统对TBTCl的毒理学敏感性,表明其可以作为监测有机锡污染程度的效应指标.     

铜在鲤体内的蓄积及毒性的研究

采用半静态法将鲤(Cyprinus carpio)暴露于不同浓度的铜溶液中,研究了铜在鱼体中的吸收富集及毒性。结果表明:铜在鲤肝、肾、鳃和肌肉中的积累量均随着铜浓度的升高而增加。鲤各部位对铜的蓄积能力依次是肝、肾、鳃、肌肉,且肝、肾中铜的积累量明显高于鳃和肌肉,鲤对铜具有较强的蓄积毒性。中毒鱼体色变黑,生长受到抑制,临死前出现神经症状;鳃小片上皮增生、变性、坏死;肝细胞和肾小管上皮细胞空泡变性、溶解性坏死。     

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).     

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.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

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.