氟苯尼考的体外抑菌作用及其对鲫抗嗜水气单胞菌感染的效果

研究了氟苯尼考对嗜水气单胞菌、副溶血弧菌、溶藻弧菌、鱼链球菌等水产动物主要病原菌的体外抑菌作用,并进一步观察了其对异育银鲫抗嗜水气单胞菌感染的效果。实验结果表明,氟苯尼考对嗜水气单胞菌、副溶血弧菌、溶藻弧菌、鱼链球菌具有良好的抗菌活性,最小抑菌浓度(MIC)分别为1mg/L、0.5mg/L、2mg/L、4mg/L。此外,投喂氟苯尼考的异育银鲫对抗嗜水气单胞菌感染具有良好的效果,以5,10,15mg/kg体重剂量将氟苯尼考拌饲投喂异育银鲫的平均死亡率与对照组相比分别降低了50%,70%,70%。     

鲤隐性败血症病原菌的分离与鉴定

本文对东北地区流行的鲤隐性败血症进行了病原菌的分离、人工感染、病原菌生理、生化特性和药物敏感性的测定,观察了病理组织变化等。从病鱼内脏分离到场22株致病菌,其中标7株的生长及生化特性均符合嗜水气单胞菌种的特性,嗜水气单胞菌hec毒素检测呈阳性。有3株菌V—P(-)、赖氨酸(-)、葡萄糖产气(-)是区别嗜水气单胞菌(Aeromonas hydrophila)及温和气单胞菌(A．Sobrie)主要特征,这三株菌符合豚鼠气单胞菌(A．Caviae)种的特征。     

齐口裂腹鱼败血症的病原分离与鉴定

从发生败血症的齐口裂腹鱼体内分离出2株致病菌，通过细菌的形态特征、培养特性和生化实验鉴定为嗜水气单胞菌和温和气单胞菌。经人工感染健康鱼表现出与自然病鱼相同的症状，并从人工感染死亡鱼中分离获得同种细菌，证实齐口裂腹鱼败血症的病原为嗜水气单胞菌和温和气单胞菌。药敏实验结果表明新霉素、头孢三嗪、庆大霉素对其高度敏感，红霉素、羧苄青霉素、氮苄青霉素和磺胺等不敏感。     

黄颡鱼暴发性流行病病原的分离鉴定及其3种毒力基因检测

为查明黄颡鱼(Pelteobagrus fulvidraco)暴发性流行病的病原菌及其3种毒力基因的携带情况,以常规方法进行细菌分离,人工感染试验确定病原菌的致病性,API 20NE和16S rRNA基因序列分析进行细菌鉴定,PCR扩增法检测病原菌的3种毒力基因。结果显示,从发病症状典型的黄颡鱼肝脏中分离到1株嗜水气单胞菌(Aeromonas hydrophila)GXGP1,与嗜水气单胞菌标准株ATCC 7966T的同源性为99.9%,对黄颡鱼有很强致病力,是引起黄颡鱼暴发性流行病的病原菌,该菌携带有Aer、hly和ahp 3种毒力基因。     

鱼类暴发性流行病治疗新方法

鱼类暴发性流行病(即白鲫出血病)是近年来在全国各地广泛流行的一种急性传染病,危害白鲫、异育银鲫、鲫鱼、团头鲂、鲢、鲮鱼等多种鱼类。据上海水产大学孙其烷等(1991)报导,异育银鲫溶血性腹水病的病原菌在上海市郊是苏伯利气单胞菌及嗜水气单胞菌,在江苏省吴县是嗜水气单胞菌。该病原菌在4～4℃及DH 5.5～     

齐口裂腹鱼感染嗜水气单胞菌后血液生化指标与组织病理学研究

为了研究嗜水气单胞菌(Aeromonas hydrophila)对齐口裂腹鱼(Schizothorax prenanti)血液生理生化指标的影响,将180尾齐口裂腹鱼平均分成6组(4、24和48 h对照组;4、24和48 h感染组)。对照组腹腔注射0.2 mL0.65%的无菌生理盐水,感染组腹腔注射0.2 mL 2.5×10~7CFU/mL的嗜水气单胞菌液。分别测定4、24和48 h对照组和感染组齐口裂腹鱼各项血液生理生化指标,并对肾脏、肝脏和肌肉组织进行病理学观察。结果显示:谷丙转氨酶、白蛋白、总胆固醇、葡萄糖、乳酸脱氢酶、钾、钠、氯、钙和磷含量均有显著变化。谷草转氨酶、碱性磷酸酶、总蛋白、球蛋白、甘油三酯则没有受到显著影响。由此可见,嗜水气单胞菌感染后对齐口裂腹鱼血液指标产生了显著的影响。对病鱼的病理学观察发现病鱼体表多处出现充血出血,溃疡和腹水,尤其是肝脏、肾脏和肌肉组织均出现不同程度的损伤,变性和局部坏死。     

载铜蒙脱石对嗜水气单胞菌粘附尼罗罗非鱼上皮细胞的影响

采用尼罗罗非鱼上皮细胞培养模型，观察嗜水气单胞菌对鳃上皮、皮肤上皮、肠上皮细胞的粘附率，研究载铜蒙脱石对细菌粘附的阻断作用及其对细菌粘附引起鱼上皮细胞膜生物特性变化的影响。结果显示：嗜水气单胞菌与鱼上皮细胞均有不同程度的粘附作用，粘附率大小顺序为鳃上皮〉皮肤上皮〉肠上皮细胞。载铜蒙脱石均显著降低了嗜水气单胞菌对鳃、皮肤和肠上皮细胞的粘附率（P〈0．05），而且对不同上皮细胞的粘附阻断率无显著差异。嗜水气单胞菌粘附肠上皮细胞后细胞膜生物特性发生了显著变化，与正常对照组相比，嗜水气单胞菌粘附鱼上皮细胞后，胞浆游离钙和细胞膜磷脂酶A2活性显著上升。载铜蒙脱石可显著降低由于嗜水气单胞菌粘附鱼上皮细胞引起的胞浆游离钙和细胞膜磷脂酶A2活性的升高。结果表明，载铜蒙脱石可有效阻断病原菌粘附，从而防治细菌感染和细菌移位。     

感染嗜水气单胞菌鱼类组织病理变化与多组学分析的研究进展

嗜水气单胞菌感染引起的病害使我国鱼类养殖遭受了严重经济损失，制约了水产养殖业的健康发展。嗜水气单胞菌可产生多种毒力因子，致病过程及影响因素复杂，感染鱼类种类广。鱼类的肠道、脾脏、肝脏和肾脏具有重要的免疫功能，在抵御病原菌入侵中发挥重要作用，其中肠道菌群直接影响着宿主的免疫和炎症反应。本文着重阐述了嗜水气单胞菌感染后鱼类免疫相关器官的组织病理学变化、转录组水平基因的差异表达和通路富集及肠道微生物组成与结构改变，综述了嗜水气单胞菌感染后鱼类病理学和组学水平变化，为研究鱼类免疫应答机制及肠道菌群免疫调节功能提供参考依据。     

嗜水气单胞菌的研究进展

嗜水气单胞菌属于弧菌科气单胞菌属,在自然界分布广泛,可以感染多种水生及陆生动物并引起不同的疾病,是一种重要的人-兽-鱼共患病病原菌。该文概述了嗜水气单胞菌的分类地位和生物学性状,并对其致病因子、鉴定方法进行了综述。     

大口鲶细菌性肠炎的病原分离和病理学研究

从大口鲶细菌性肠炎的病鱼中，分离出二株病原菌，经人工感染健康大口鲶表现出较强的致病力，出现与自然病鱼相同的症状。证实这二菌株是大口鲶细菌性肠炎的病原菌。对菌体形态特征、培养特性和生理生化反应的鉴定证明为嗜水气单胞菌。细菌性肠炎的病理学研究结果表明为淋巴细胞侵润为主的炎性病变。并探讨细菌性疾病的致病原理。     

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.     

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.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

Effects of cadmium on the kinetics of calcium uptake in developing tilapia larvae, Oreochromis mossambicus

The toxic effects of Cd²⁺ on Ca²⁺ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l^-1 of Cd²⁺ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca²⁺ uptake within 4h resulting in a great increase in K_m values for Ca²⁺ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca²⁺ influx of larvae in solutions of 0.2 mM Ca²⁺ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd²⁺ than 0 day-old larvae. Although the Ca²⁺ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l^-1 Cd²⁺ solution, total body Ca²⁺ content was significantly reduced in 3 day-old larvae. Increased Ca²⁺ uptake efficiency ensures sufficient Ca²⁺ for normal growth. However, rapid increase in Ca²⁺ influx after hatching also leads to higher Cd²⁺ uptake. Exposure to Cd²⁺ will lead to a drop in body Ca²⁺ content resulting in retardation of larval growth. Therefore, we conclude that if Ca²⁺ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca²⁺ and will show signs of Cd²⁺ poisoning.     

Migratory dynamics of stream-spawning longnose gar (Lepisosteus osseus)

Abstract– Literature evidence suggests that lake-dwelling longnose gar (Lepisosteus osseus) enter tributary streams to spawn, Until the present study, the dynamics of this breeding migration had never been investigated quantitatively. During the summers of 1991 and 1992, longnose gar were captured as they entered Weaubleau Creek, Missouri, a tributary of Harry S. Truman Reservoir. The in-stream spawning migration began in early April and ended in late May, and was positively correlated with stream flow and water level, and negatively correlated with water temperature. In-stream residence times ranged from 15 to 94 days, with males exhibiting longer residence times than females. Once in-stream, longnose gar travelled as far as 10 km upstream and occupied certain pools at greater relative frequencies. Although the reason for this preferential utilization is not completely understood, it may relate to pool depth and riffle proximity. Longnose gar disperse from the spawning stream great distances, with gar captured in Weaubleau Creek being recaptured up to 48 km away. This information should provide fisheries biologists the means to consider the reproductive ecology of this species in their conservation and management decisions.     

Nutritional regulation of hepatocyte fatty acid desaturation and polyunsaturated fatty acid composition in zebrafish (Danio rerio) and tilapia (Oreochromis niloticus)

The desaturation and elongation of [1-¹⁴C]18:3n-3 was investigated in hepatocytes of the tropical warm freshwater species, zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus). The hepatocyte fatty acid desaturation/elongation pathway was assayed before and after the fish were fed two experimental diets, a control diet containing fish oil (FO) and a diet containing vegetable oil (VO; a blend of olive, linseed and high oleic acid sunflower oils) for 10 weeks. The VO diet was formulated to provide 1% each of 18:2n-6 and 18:3n-3, and so satisfy the possible EFA requirements of zebrafish and tilapia. At the end of the dietary trial, the lipid and fatty acid composition was determined in whole zebrafish, and liver, white muscle and brain of tilapia. Both zebrafish and tilapia expressed a hepatocyte fatty acid desaturation/elongation pattern consistent with them being freshwater and planktonivorous fish. The data also showed that hepatic fatty acid desaturation/elongation was nutritionally regulated with the activities being higher in fish fed the VO diet compared to fish fed the FO diet. In zebrafish, the main effect of the VO diet was increased fatty acid Δ6 desaturase activity resulting in the production of significantly more 18:4n-3 compared to fish fed the FO diet. In tilapia, all activities in the pathway were greater in fish fed the VO diet resulting in increased amounts of all fatty acids in the pathway, but primarily eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). However, the fatty acid compositional data indicated that despite increased activity, desaturation of 18:3n-3 was insufficient to maintain tissue proportions of EPA and DHA in fish fed the VO diet at the same level as in fish fed the FO diet. Practically, these results indicate that manipulation of tilapia diets in commercial culture in response to the declining global fish oil market would have important consequences for fish fatty acid composition and the health of consumers. Scientifically, zebrafish and tilapia, both the subject of active genome mapping projects, could be useful models for studies of lipid and fatty acid metabolism at a molecular biological and genetic level. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of diatom–bacteria biofilm isolated from Seriola lalandi cultures for aquaculture application

Controlled incorporation of selected microalgae and bacteria in aquaculture systems can be beneficial because they can act as microbiological control. That is why the characteristics of biofilm generated naturally in Seriola lalandi culture cages were analysed, their potential benefit to the growth of larvae was studied, and their controlled use for improving the larval viability and as a vector to improve incorporation of previously studied probiotic bacteria was tested. According to biodiversity results, these biofilms are composed of a diatom–bacteria mix showing a decrease in biodiversity in laboratory culture conditions being dominated by Navicula phyllepta and bacteria of the family Rhodobacteraceae. This can be produced on mesh substrates incorporated in bioreactors with rapid growth rate and adhesiveness. Preliminary results from the addition of substrates with this specific biofilm in larvae culture systems showed that it is consumed by the larvae without negative effects, while positive effects on the viability of larvae in combination with probiotics were observed. Considering preliminary results, the addition of these specific substrates with diatom–bacteria biofilms could be a good improvement for aquaculture systems and together with the use of probiotics can contribute to maintaining a stable and controlled system improving the viability of the larval fish culture in its early stages.