额尔齐斯河粘鲈感染复口吸虫的种群动态研究

通过对额尔齐斯河粘鲈(Acerina cernua)的取样调查研究,揭示了其感染复口吸虫(Diplostomum)的种群生态学的部分特点。2009年4月至2013年4月随机选取额尔齐斯河河段内的北屯、哈巴河为采样点进行采样调查。共采集解剖体长5~13 cm粘鲈129尾。结果表明,复口吸虫的总感染率为38.76%,平均感染强度为16.06±30.85,感染0、1~5、6~10、11~15、16~20和20只以上复口吸虫的粘鲈占粘鲈总数的比率分别为61.24%、24.03%、3.88%、1.55%、1.55%和7.75%。复口吸虫感染率和感染强度随着粘鲈体长的变化而发生变化:感染率在13 cm以上的粘鲈中达到最大,为80%;平均感染强度在11 cm≤L13 cm范围内最大。感染强度在体长段5 cmL≤7 cm与9 cmL≤11 cm和11 cmL≤13 cm之间存在显著性差异。复口吸虫种群在宿主不同体长段中的分布类型均为聚集分布,且聚集强度随宿主体长的变化而发生变化。     

伊犁河流域新疆裸重唇鱼寄生三代虫的感染情况及空间分布

2019年对新疆伊犁河流域巩乃斯河段鱼类进行寄生虫病原调查过程中发现,在新疆裸重唇鱼(Gymnodiptychus dybowskii)体表有三代虫寄生,经形态学特征及分子生物学鉴定确定为同一种三代虫,定为新种(暂未公布)。为了解该三代虫在新疆裸重唇鱼鳍条上的寄生特点,运用统计学方法对新疆裸重唇鱼鳍条寄生三代虫的感染情况及空间分布特点进行分析。结果显示:在检查的69尾新疆裸重唇鱼中,共检出459只同种三代虫,总感染率和平均感染丰度分别为91.3%和(6.65±5.24);统计三代虫在各个鳍条的感染率,腹鳍的感染率最高为78%,尾鳍感染率最低为41%,在宿主胸鳍与尾鳍之间的感染强度差异显著;三代虫随着宿主体长的增大,其感染率、感染丰度和强度逐渐上升,在14～19 cm体长组达到最高,不同大小的宿主其感染强度之间差异显著。结果表明,新疆裸重唇鱼寄生三代虫对宿主体长及鳍条具有一定的选择偏好性,更偏好寄生于体长14～19 cm的宿主的胸鳍。三代虫在宿主种群中的分布类型为聚集分布和均匀分布。     

叶尔羌河流域斑重唇鱼寄生单式指环虫的空间分布

为了解单式指环虫在斑重唇鱼(Diptychus maculates)鳃部寄生的空间分布特点, 于 2019 年 5 月至 2020 年 6 月对新疆叶尔羌河流域斑重唇鱼进行了 3 次取样调查, 运用统计学方法对斑重唇鱼鳃部寄生单式指环虫(Dactylogyrus simplex)的感染情况及空间分布特点进行分析。结果显示, 在检查的 325 尾斑重唇鱼中, 共检出 3994 只单式指环虫, 总感染率和平均感染丰度分别为 67.7%和 12.3±1.2; 左鳃及右鳃的感染率分别为 59.4%和 57.2%, 两者之间的感染丰度无显著差异(P＞0.05); 在各鳃片中, 鳃Ⅰ(最靠近鳃盖的鳃片)、鳃Ⅱ的平均感染丰度显著高于鳃Ⅳ(P＜0.01); 单式指环虫随着宿主的生长, 其感染率、感染丰度和强度先上升, 后下降, 在 13~18 cm 体长组达到最高, 但是各体长组间的感染没有显著差异(P＞0.05)。结果表明, 单式指环虫对宿主左右鳃和年龄没有选择偏好性, 但在鳃片分布上更偏好寄生于鳃Ⅰ和鳃Ⅱ, 单式指环虫在宿主种群中的分布类型为聚集分布。     

额尔齐斯河河鲈复口吸虫的空间分布研究

2009年7月至2014年8月,对额尔齐斯河河鲈(Perca fluviatilis Linnaeus)进行采样调查,运用统计学方法分析河鲈眼睛寄生复口吸虫(Diplostomum)的空间分布特点。结果表明,在检查的253尾河鲈中,复口吸虫总感染率为51.38%,左右眼晶状体的感染率分别为11.86%和9.09%,左右房室液的感染率分别为40.32%和30.04%;方均比均大于1,表明复口吸虫种群呈聚集分布,且L房和R房聚集强度为50.63和34.97,高于L晶和R晶3.18和5.58;单因素方差分析各体长组复口吸虫感染数量,发现不同体长段在L晶和R晶差异不显著(P0.05),在L房和R房差异显著(0.01≤P0.05,P0.01)。复口吸虫在晶状体和房室液的分布存在显著差异,对于晶状体和房室液有明显的选择性。     

孤岛指环虫寄生于斑尾刺鱼(鱼叚)虎鱼鳃空间分布的研究

通过对斑尾刺(鱼叚)虎鱼鳃上孤岛指环虫空间分布的研究发现,随着宿主体长的增加,其平均密度、感染强度及感染率均呈下降的趋势;从春季到秋季,孤岛指环虫的平均密度、感染强度和感染率均呈上升趋势,冬季呈迅速下降的趋势;斑尾刺鱼叚虎鱼鳃上孤岛指环虫的分布频率,表明大量的孤岛指环虫寄生于少数宿主鳃上,多数宿主感染少量的孤岛指环虫;孤岛指环虫种群在不同体长的宿主和不同季节均呈聚集性分布.     

惠东拟囊腔吸虫种群动态研究

鲻体内的惠东拟囊腔吸虫（Ｓａｃｃｏｃｏｅｄｉｏｉｄｅｓ ｈｕｉｄｏｎｇｅｎｓｉｓ Ｌｕｅ,１９９３）随着宿主体长的生长,其感染强度,平均密度有逐渐增加的趋势,而感染率则呈不规划的波动;其感染率、感染强度和平均密度在不同月份亦呈不稳定变化;吸虫在宿主体内的频率分布表明,大量的吸虫寄生于少数宿主中,而多数宿主感染少量的吸虫;吸虫在不同体长组的分布类型为聚集分布,且聚集强度随种群密度的增加而增大。     

加州鲈非细菌性疾病及其防治

１ 车轮虫病１．１ 病 因 由原虫类的多种车轮虫寄生于加州鲈体表及鳃部感染引起。１．２ 症状 病鱼体黑而瘦，食欲减退或不摄食，群游于池边。大量寄生时，鳃组织分泌大量粘液，鳃丝发白腐烂，严重时池边慢游最后死亡。１．３ 危害及流行情况 ４～５月份最为流行。对鱼苗、鱼种危害较大。该病传播速度快，感染率高，感染强度大，且易继发感染。１．４ 防治方法 １）生石灰彻底清塘，杀灭病原体；２）注意放养密度和保持水质清新；３）苗种入池前用３％食盐水浸洗３～５分钟；４）全池泼洒０．７ ｇ／ｍ３硫酸铜、硫酸亚铁合剂（５：２），…     

新疆河鲈繁殖生态学参数的解析

在为期４年（１９８７－１９９０年）的新疆乌伦古湖渔业资源考察中，从来自各湖区的渔船中随机抽样了１１１６１尾河鲈标本，对其年龄、体长、体重进行了统计。解剖测定了２８８０尾标本的性腺怀卵量、性比、性成熟系数。利用这些生态学参数建立了性腺发育周期模型及关于繁殖力的各项模型并编制了生命表，分析了河鲈产卵群体的性成熟时间与结构，以期对河鲈的人工引种和驯化提供理论依据。     

额尔齐斯河东方欧鳊寄生奇异双身虫的种群生态学研究

通过2009年4月至2010年1月在额尔齐斯河(中国段)野外取样调查,研究寄生于东方欧鳊(Abramis brama orientalis)鳃部的奇异双身虫(Diplozoon paradoxum)的种群生态学特点。结果表明,东方欧鳊感染奇异双身虫的总感染率为24.16%,平均感染强度为4.19,在宿主体长L≤30 cm时,感染率随体长增大有升高的趋势;在体长25 cmL≤30 cm时,感染率达到最大,为42.11%;而体长L30 cm的宿主,没有感染奇异双身虫。奇异双身虫在东方欧鳊各体长段均呈聚集分布。     

额尔齐斯河温氏指环虫的种群生态学研究

2009年4月至2010年1月对额尔齐斯河(中国段)东方欧鳊(Abramis brama orientalis Berg)鳃部寄生的温氏指环虫(Dactylogyrus wunderi Bychowsky)进行了取样调查,以期了解温氏指环虫的种群生态学特点。结果表明,温氏指环虫的总感染率为12.92%,平均感染强度为5.70(1～19)。感染率、感染强度在不同体长组的宿主中表现出不同的变化趋势,随着宿主体长(L)的增大,温氏指环虫的感染率在35cm以上的宿主中达到最大,为50%,而平均感染强度在20≤L<25的体长范围内最小,为1.75;温氏指环虫种群在不同体长组宿主中的分布类型主要为聚集分布,且各体长段宿主之间的感染强度差异不显著(P>0.05)。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

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 performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

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).     

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.     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

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.