斑尾刺鰕虎鱼体内岐口福斯特吸虫的种群动态研究

通过对斑尾刺鰕虎鱼（Acanthogobius ommaturus）肠道内岐口福斯特吸虫（Faustula qikouensis）种群动态的研究发现,随着宿主体长的增加,其平均密度、感染强度及感染率均呈上升趋势;在宿主体长小于26.5cm时,其种群平均拥挤度、扩散性指标随着鱼体长的增加而增大,分布参数k值则呈减小趋势。...     

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。     

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.     

额尔齐斯河白斑狗鱼复口吸虫的流行病学调查

调查白斑狗鱼眼内寄生的复口吸虫的流行病学,为白斑狗鱼养殖过程中的疾病防治提供基础性资料。2009年至2014年在中国境内的额尔齐斯河8次采样获得263尾白斑狗鱼,统计分析复口吸虫在白斑狗鱼各体长组中的频率分布及空间分布特点。结果表明:复口吸虫一年四季均可感染白斑狗鱼,感染率从春季到冬季逐渐升高,冬季达到峰值;平均感染强度则在冬季最高,夏季次之,春秋两季均低;总感染率为34.98%,平均感染强度为10.74只/尾;感染率随宿主体长增加而上升,但是在体长50 cm时,感染率最低,为4.17%;平均感染强度随宿主体长的增加也呈逐渐上升的趋势;方均比在各体长段均大于1,呈聚集分布,且聚集度随鱼体长增加而增加。     

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。     

鳔等睾吸虫在长吻鱼危体内寄生的初步研究

解剖检查了 5 8尾体长在 35 0cm以下的长吻鱼危 ,统计表明 :宿主感染鳔等睾吸虫的感染率为2 5 9% ,平均感染强度是 3 5。在 15 0cm以下的长吻鱼危体内未检出鳔等睾吸虫。鳔等睾吸虫由 2 0～ 10 0mm的虫体组成 ,在宿主种群中呈聚集分布。宿主染虫较多时对其正常生长有明显的影响     

鳔等睾吸虫在长吻Wei体内寄生的初步研究

解剖检查了58尾体长在35.0cm以下的长吻Wei，统计表明，宿主感染鳔等睾吸虫的感染率为25．9％，平均感染强度是3．5。在15.0cm以下的长吻Wei体内未检出鳔等睾吸虫。鳔等睾吸虫由2．0－10．0mm的虫体组成，在宿主种群中呈聚集分布，宿主染虫较多时对其正常生长有明显的影响。     

澧水下游水系黄鳝感染鳗鲡独孤吸虫的研究

产于澧水下游水系的黄鳝对鳗鲡独孤吸虫的总感染率为46 7%,感染强度为3 14(1～11)。体长24cm以下的黄鳝未检出该种吸虫;体长29 1cm以上的黄鳝均有较高的感染率(50%以上),且差异不大,其感染强度亦无显著性差异。鳗鲡独孤吸虫种群主要由体长3～5mm的虫体组成,在黄鳝种群中呈聚集分布,其负二项分布参数k=0 377。鳗鲡独孤吸虫的寄生对黄鳝肥满度有一定影响,使黄鳝肥满度系数平均下降9 8%。     

洞庭湖黄鳝体内鳗鲡独孤吸虫种群生态研究

洞庭湖黄鳝对鳗鲡独孤吸虫的总感染率为 5 1 7% ,感染强度为 4 6 7(1～ 33) ,其中以体长 2 9 1～39cm的黄鳝感染率最高 ,其余体长的黄鳝也有较高的感染率 (37 5 %以上 )。其感染强度有随体长的增长而增大的趋势。鳗鲡独孤吸虫种群主要由体长 3～ 8mm的虫体组成 ,在黄鳝种群中呈聚集分布。鳗鲡独孤吸虫的寄生对黄鳝肥满度无明显影响。     

长江丽棘虫在粗唇鱼危肠道内分布的研究

对 1 0 8尾粗唇鱼危肠内长江丽棘虫种群的研究表明 ,粗唇鱼危体长 8 0～ 1 2 0cm组长江丽棘虫感染率是 88 9% ,体长 1 2 1～ 2 9 3cm感染率为 1 0 0 %。随着粗唇鱼危体长增长 ,其感染长江丽棘虫的感染强度增大。长江丽棘虫种群主要由 2 5～ 6 5mm长度的虫体组成 ,种群中雌虫显著多于雄虫。 84 0 %的虫体附着在粗唇鱼危肠道的前段。长江丽棘虫在不同体长段的宿主中均呈聚集分布 ,聚集强度各不相同。     

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.     

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.     

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).     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.     

Cardiac,ventilatory and metabolic responses of two ecologically dissimilar species of fish to waterborne cyanide

Changes in heart rate, ventilatory activity and oxygen consumption were determined in trout (Salmo gairdneri) and brown bullhead catfish (Ictalurus nebulosus) during exposure to a steadily increasing concentration of waterborne cyanide selected to produce death in 8–9 hours for each species. The lethal cyanide concentration for the bullheads was an order of magnitude higher than for trout. Trout developed an immediate and gradually increasing bradycardia throughout the exposure period. Cyanide produced tachycardia in the bullhead followed by a gradual onset of bradycardia as the concentration of cyanide was raised. Pericardial injection of atropine (a muscarinic cholinergic antagonist) indicated that bradycardia in the trout was due initially to increased vagal tone but later due to the direct effect of cyanide on the heart. Hyperventilation in the trout persisted throughout the exposure period, although the rate and amplitude fluctuated and was variable between individual fish. During the last hour of exposure (highest cyanide concentration), ventilation was characterized by rapid, shallow breaths followed by a sudden respiratory arrest. The bullheads exhibited hyperventilation during the first 3 hours of exposure followed by a gradual, linear drop in ventilation rate and amplitude until death occurred. Cardiac and ventilatory responses in both species were attributed to stimulation of central and peripheral chemoreceptors by cyanide. Evidence is presented which suggests the initial response in the bullheads was due, at least in part, to gustatory stimulation by the cyanide. Oxygen consumption of the trout remained above pre-exposure levels for the majority of the test period. Oxygen consumption in the bullhead paralleled the changes in heart and ventilatory rates. Whole-body lactate levels of fingerlings of both species during cyanide exposure were measured to estimate the extent of anaerobiosis. Whole-body lactate levels were much greater in the bullheads than the trout, indicating a higher capacity for anaerobiosis, possibly due to a greater fuel supply. Overall, the trout responded to cyanide in a manner similar to that produced by environmental hypoxia whereas the bullheads experienced a gustatory stimulus which masked the hypoxia-like response.     

An overview of stress physiology of fish transport: changes in water quality as a function of transport duration

This study brings an integrated analysis about the relationship between water deterioration and its physiological consequences in live fish transport. The analysis was focused on the transport water and its deterioration, and physiological challenges imposed on the fish. Usual commercial handling procedures employed to mitigate fish stress during transport were discussed. Future topics of research for the establishment of safer fish transport protocols were proposed. Transport was classified into short (≤8 h) or long transport (>8 h). The main issue in short transports should be the prevention of water pH reduction, while in long transports it is the increase in ammonia. Plasma cortisol is the most employed marker for stress and is acutely elevated upon short episodes of transport, but remains elevated even in long‐transport events. Plasma glucose is perhaps a better marker for handling stress. Plasma lactate, pH, osmolality CO₂ and ions should be more often evaluated. Plasma Na⁺ and Cl^‐ are very useful markers of acidosis, due to their respective exchange for H⁺ and , for acid–base regulation. The establishment of species‐specific transport protocols should be preceded by such combined analyses of water and physiological parameters.