光、温对鼠尾藻卵子排放和幼孢子体生长的影响

以成熟的鼠尾藻生殖托为材料,研究了不同温度(13～23℃)、光照度(3000～12000lx)和光照周期(15L∶9D,12L∶12D,9L∶16D)对鼠尾藻排卵及幼孢子体生长的影响。结果显示,温度在20～23℃范围,有利于鼠尾藻卵子的排放;在3000～12000lx范围内,光照度越高,越有利于鼠尾藻卵子的排放;光周期不是影响卵子排放的主要因素,光照度是鼠尾藻幼孢子体生长的重要因子;温度是制约鼠尾藻幼孢子体生长的关键因子,水温低于16℃时不利于幼孢子体的快速生长。     

四爿藻培养条件的研究

在实验室模拟条件下,研究了温度、光照、盐度、pH值和营养盐对四爿藻生长繁殖的影响。结果表明:四爿藻生长的适宜温度为5~30℃,最适温度为20℃;适宜光照为500~10 000 lx,最适光照为4 000~7 000 lx;适宜盐度5~85,最适盐度为35;适宜pH值为4~9,最适pH值为7。筛选出四爿藻的培养液配方是,天然海水加入(NH2)2CO-N60 g/m3;KH2PO4-P 2 g/m3;FeC6H5O7-Fe 0.4 g/m3;维生素B11 g/m3和维生素B120.000 5 g/m3。     

温度、光照度、盐度和pH对颤藻生长的限制条件研究

颤藻(Oscillatoria sp.)是对虾养殖池塘中的常见蓝藻,其大量繁殖直接危害对虾养殖.实验旨在通过研究不同温度、光照度、盐度和pH对颤藻生长的影响,得出颤藻生长的限制条件.单因子实验结果显示:实验条件范围内,温度、光照度、盐度和pH对颤藻叶绿素a含量和干重影响显著(P＜0.05),温度＜10℃和＞30℃、光照度＜50 lx和＞1100 lx、盐度＜15和＞30、pH ＜5.2和＞8.0是颤藻生长的限制条件;颤藻生长的阈值为温度10℃,光照度50 lx,盐度15.0,pH5.2;正交实验结果显示,颤藻生长的最低条件为温度15℃、光照度600 lx、盐度17.5、pH 5.5,温度对颤藻叶绿素a含量和干重影响最大,其次是盐度和pH.对虾养殖池可以通过调节盐度来控制颤藻生长.     

温度、光照强度对舌状蜈蚣藻早期发育的影响

舌状蜈蚣藻（Grateloupia livida）是一种具有较高应用价值的红藻。文章研究了不同的温度（15℃、20℃、25℃和30℃）和光照强度（500 lx、2500 lx、5 000 lx和10 000 lx）对舌状蜈蚣藻早期发育的影响。试验结果表明,舌状蜈蚣藻适合果孢子发育为盘状体的条件为温度25℃、光照5 000 lx。果孢子在25~30℃条件下首先形成盘状体,15℃下形成最慢;盘状体在25℃首先长出直立枝,其次是20℃、15℃和30℃。果孢子在5 000~10 000 lx的光照强度下首先形成盘状体,2 500 lx次之;在盘状体发育过程中较高光强可以促进盘状体的生长发育,低光强培养条件显著抑制了盘状体的生长发育。     

环境因素对淡水浮丝藻生长及产生嗅味的影响

研究温度、营养盐浓度以及光照强度对淡水浮丝藻(Planktothrix sp.)及其代谢产物二-甲基异莰醇(2-MIB)的影响,为控制丝状蓝藻生长及预警水体嗅味物质污染提供实践依据。浮丝藻由中国科学院水生生物研究所淡水藻种库分离于安徽巢湖;设置的实验温度为15、20、25、30℃,BG-11营养盐溶液体积分数为20%、30%、50%、100%,光照为1 000、2 000、3 000、4 000 lx。结果表明,温度对浮丝藻生长密度、总2-MIB生成量及胞外2-MIB分泌量影响最显著,25℃是浮丝藻最适宜生长温度,最高细胞密度可达6.04×10⁵个/mL,30℃是其最适宜的产2-MIB温度,总2-MIB生成量和胞外2-MIB分泌量均最高,分别为3.64×10³ng/L和2.78×10³ng/L;其次为营养盐浓度,增大BG-11营养盐浓度,浮丝藻生长密度和总2-MIB生成量会随之增加,低浓度营养盐时胞外2-MIB分泌量所占比例较高,表明低浓度营养盐更有利于浮丝藻进行胞外2-MIB分泌;光照对浮丝藻生长及产嗅味物质影响较小,...     

不同培养条件对长紫菜叶状体生长及生理响应的研究

为探索长紫菜在不同培养条件下的生理响应,研究了在不同温度、盐度和光照培养条件长紫菜叶状体的生长及生理响应,主要测定藻体的生长、光合色素、可溶性蛋白和丙二醛(MDA)含量、抗氧化酶活性等生理指标的变化。结果表明,在培养温度为17～20 ℃时,长紫菜藻体可以保持较高相对生长速率,当温度高于23 ℃时,其生长明显受到抑制,藻体发红并出现溃烂;长紫菜叶状体在盐度25～35下可以保持较快生长,在低于盐度25的条件下,藻体的光合色素、可溶性蛋白、丙二醛(MDA)的含量以及过氧化物酶(POD)、过氧化氢酶(CAT)活性均产生显著的变化,并观察到藻体变薄、发白、腐烂现象;在光照为3 000～6 000 lx时,藻体生长速率较为稳定,藻体在光照为9 000 lx条件下的叶绿素a含量低,可溶性蛋白和MDA含量以及POD活性都出现显著增高,并观察到发红及溃烂现象。因此,适合长紫菜叶状体生长的温度为17～20 ℃,盐度为25～35,光照在6 000 lx左右。     

人工培养条件下环境因子对微小小环藻生长的影响

在实验室培养条件下,研究了温度、光照、盐度、pH值和氮、磷、铁、硅等营养盐对微小小环藻(Cyclotella caspia)生长繁殖的影响。实验结果表明:微小小环藻生长的适宜温度为10～40℃,最适温度为30～35℃;适宜光照为500～10 000 lx,最适光照为2 000～8 000 lx;适宜盐度为2～85,最适盐度为25～50;适宜pH值为4～9,最适pH为8.0～8.5。筛选出微小小环藻培养液配方是每立方米海水加入(NH2)2CO-N 30g,NaH2PO4-P 1 g,FeC6H5O7-Fe 0.1 g,Na2SiO3-Si 25 g。     

小新月菱形藻生长条件及半连续培养条件研究

为研究温度、光照和营养盐对小新月菱形藻生长的影响,设计了5个温度,3个光照度,各种营养盐各4个浓度以及6个更新率,进行了小新月菱形藻的培养试验。结果表明:小新月菱形藻的最佳生长温度为15～20℃,最佳光照度为5000 lx,氮、磷、硅、铁的最佳浓度依次为300、15、120、1.575 mg/L;当温度高于30℃或者光照度大于10000 lx时,小新月菱形藻均不能生长。对小新月菱形藻进行半连续培养条件的研究发现,小新月菱形藻在6个不同的更新率(25%、30%、35%、40%、45%和50%)条件下均能完成半连续培养。根据不同更新率下的细胞密度和实际生产中的培养密度,建议采收率在40%～45%。     

生态和营养条件对日本星杆藻生长的影响

日本星杆藻(Asterionella japonica)是浮游动物的良好食物,也是发生赤潮的藻类物种,研究生态和营养条件对日本星杆藻生长的影响,对合理利用和防止赤潮的发生具有重要的意义。本文通过室内单因子正交实验,研究了温度、光照、盐度、pH值以及氮、磷、铁、硅和维生素B12等营养元素对日本星杆藻生长的影响,结果表明:该藻生长的适宜温度为10~35℃,最适温度为20℃;适宜光照为500~8 000 lx,最适光照为1 000lx;适宜盐度为5~45,最适盐度为20~35;适宜pH值为5~9.5,最适pH为8.0。在培养用的1 m3天然海水中添加20 g(NH2)2CO3、0.5 g NaH2PO4、10 g Na2SiO3、0.005 g维生素B12,日本星杆藻的生长最快。     

温度和光照条件对裙带菜配子体生长的影响

通过设置不同的培养条件,检验温度、光照强度和光照周期对裙带菜雌配子体生长的影响。第一步设置3个温度条件(12℃、16℃、20℃)和5个光照强度条件(1 000、1 500、2 000、2 500、3 000lx)进行全析因方差设计,得出最适温度条件和光照强度;第二步,在最适温度条件下,设置2个光照周期(24h持续光照和光暗周期D∶L=12∶12)和不同光照强度,检验不同光照强度条件和光照周期对配子体生长的影响。在以上实验的基础上,根据最适温度条件和光照周期,设置不同光照强度检验其对配子体鲜重量生长的影响。实验结果显示:裙带菜雌配子体最适宜的在温度为16℃,光照强度为2 500lx,周期为24h持续光照。     

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.