几个因子对内蒙古自治区卤虫卵孵化率的影响

采用常温、冷冻和盐水浸泡的方法.用3％双氧水、3％甲醛和3％高锰酸钾处理卤虫卵,研究诸因子对卤虫卵孵化率的影响。试验结果表明:产于内蒙古自治区的卤虫卵最佳孵化盐度为35;用3％双氧水和3％甲醛处理卤虫卵均能提高其孵化率;用粗盐饱和溶液处理是保存卤虫卵的好办法。     

冷冻等处理对不同孵化进程的卤虫卵存活率的影响

本文研究了冷冻、双氧水和干燥处理对处于不同孵化进程中的卤虫卵的存活率（孵化率）的影响。冷冻对未经孵化处理的卵的孵化率影响很小，冷冻1-8周，基本保持不变。孵化进行了3个小时的卤虫卵，冷冻8周后，其孵化率降低了10个百分点。孵化进行了6个小时的卤虫卵，冷冻8周后，其孵化率降低了31个百分点。孵化进行79个小时的卤虫卵，冷冻8周后，其孵化率降低740个百分点。处于不同孵化阶段的卤虫卵经冷冻处理8周后，再经3％双氧水处理10分钟和40℃干燥处理6小时，其孵化率表现为不同的特点。未经孵化处理卵的孵化率基本保持不变。孵化进行了3个小时的卤虫卵，其孵化率再次降低5个百分点。孵化进行了6个小时的卤虫卵，其孵化率再次降低了20个百分点。孵化进行79个小时的卤虫卵，其孵化率再次降低了37个百分点。     

卤虫卵孵化强化剂的初步研究

对不同品系的低孵化率卤虫卵进行了孵化对比试验，分为试验组和对照组，其中试验组添加孵化强化剂与对照组进行同等条件的试验，2组对照组的孵化率分别是66．8％、64．9％，试验组的孵化率分别是84．3％、81．5％增幅超过15个百分点，说明这种针对低孵化率卤虫卵研制的强化剂有效可行，可做进一步推广试验。     

不同品系卤虫卵孵化质量的比较

对新疆艾比湖、青海格尔木、青海尕海、河北乐亭、河北沧州、河北南堡六个品系卤虫卵的孵化质量做了一些初步研究。南堡、艾比湖、沧州、乐亭、格尔木、尕海卤虫卵的孵化率分别为82．7％，80．2％，75．3％，66．O％，62．2％，10.1％；孵化的同步性分别为4．8，11．2，17．0，11．2，11．5，23．2h。孵化质量最好的是河北南堡的卤虫卵。     

卤虫卵孵化强化剂的初步研究与应用

对两种不同品系的卤虫卵进行了孵化对比实验,分别分为实验组和对照组两组,其中实验组添加孵化强化剂,其他孵化条件与对照组相同。两组对照组的孵化率分别为80.3％和79.6％,而加入孵化强化剂之后的实验组的孵化率分别为85.3％和86.4％,增幅范围为5％～10％。从而更加说明了孵化强化剂型的显著效果,为进一步的中试奠定了基础。     

一种新型聚维酮碘制剂对卤虫卵及无节幼体的活体消毒试验

为了解一种新型的聚维酮碘制剂对卤虫卵及无节幼体的消毒杀菌效果,研究了该聚维酮碘制剂对卤虫卵和无节幼体的毒性以及对3种不同产地卤虫卵孵化率的影响,并进行了卤虫活体和孵化水的灭菌试验。结果显示,该聚维酮碘制剂在极高浓度(20000 mg/L)下,长时间(60 min)浸泡对市售卤虫卵孵化率无影响,并且未引起卤虫无节幼体死亡,毒性极低;试验分离到市售卤虫携带的4种优势细菌,分别为Vibrio tubiashii、V.sinaloensis、V.anguillarum和Uncultured V.sp.,以浓度500 mg/L的该聚维酮碘制剂处理30min后,可将孵化水中的细菌几近全部杀死(细菌存活率为1.67%);在试验浓度(2 000 mg/L)下,聚维酮碘对渤海湾盐田卤虫卵和巴里坤盐湖卤虫卵的孵化率无影响,但浓度在500 mg/L及以上时,俄罗斯进口卤虫卵的孵化率显著下降。试验结果表明,该聚维酮碘制剂可以作为优良的卤虫消毒剂,建议生产上使用浓度为200~500 mg/L。     

两种卤虫休眠卵的终止滞育及休眠卵的诱导发生

诱导大盐湖卤虫（Artemia.francisana)和东营卤虫（Artemia.sinina)产休眠卵，作为研究对象探讨了最适终止滞育的方法，结果表明：用20℃冰冻20d，3%的H2O215min处理对大盐湖卤虫休眠卵最有效，而4℃下饱和卤水浸泡25d对东营卤虫休眠卵最有效，研究还发现在不同盐度和温度的组合培养条件下得到的休眠卵，用同一种终止滞育方法处理后，其孵化育不同。     

卤虫(Artemia salina)形态习性的初步观察

本文利用我国北方塘沽盐场产的卤虫(Artemia salina)休眠卵作为孵化培养的试验材料,对卤虫的形态进行解剖观察并作详细叙述。卤虫以单细胞藻及有机碎屑为饵。一生中经过无节幼虫期、后无节幼虫期、拟成虫期和成虫期的变态过程。在这一过程中要经过多次蜕皮,每蜕皮一次,身体就长大一次。雌雄虫的形态区别主要在于第二触角和生殖器官。雄虫一般极为少见。雌虫产两种类型卵子:休眠卵和非休眠卵。后者为孤雌生殖。卤虫的生长和性成熟与其水温等有关系。水温高,生长成熟都比较快。水温还和休眠卵的孵化速度有关。平均水温20.8℃时,经46小时开始孵化;25℃经24小时开始孵化;29.5℃经12小时开始孵化。孵化水的波美氏度(卤度)以4—5度最为合适。在缺乏光照时,孵化率大为下降。卤虫无节幼虫是世界海产鱼、虾幼体的著名活饵料。因此,对其孵化、培养条件的进一步探讨是很有必要的。     

盐度、pH及孵化时间对卤虫孵化率的影响

<正> 卤虫早期幼体营养丰富,作为鱼、虾、蟹幼体的饵料,在水产育苗中已被广泛采用,但对其孵化所需盐度、pH及孵化时间意见不一。本文就这几个因子对卤虫孵化率的影响进行了试验总结。 试验用卤虫卵系采自河北省海兴的冬卵。卵取回后经漂洗、沉淀去杂质,在-28～—30℃速冻,存放于-18℃冷库中。用前取     

小卤虫 大产业——加速开发持续利用我国丰富的卤虫资源

卤虫又名“丰年虫”、“丰年虾”,是高盐度水域繁生的一类小型甲壳动物,含有丰富的蛋白质及多种营养成分,无节幼体是鱼、虾、蟹育苗的优质鲜活饲料,成体是鱼、虾、蟹及家禽等养殖的精饲料。我国预计到2000年时年需要量2000吨卤虫卵。世界各国的需求量也在逐年增加。因此,卤虫个体虽小(成体仅1—1.7cm),经济价值却极高,尤其是细砂状的卤虫冬卵,每克20多万粒,在国际市场每吨售价2—3美元,高的可达5万美元。开发卤虫资源前景广阔。 我国沿海盐田及内陆盐湖、盐场面积很大,卤虫成体和卤虫卵产量均超过世界其它国家的总和。仅目前已开始利用的盐湖、盐场估计,天然卤虫卵年产量可超     

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.