鱼类利用碳水化合物的研究进展

鱼类对碳水化合物的消化和代谢能力较差,缺乏对血糖水平的调控能力。众多的研究资料表明,摄入高碳水化合物通常会导致鱼体出现持续的高血糖、肝肿大、肝糖原累积、生长率和饲料效率降低。影响鱼类利用饲料碳水化合物的因素很多,包括鱼的食性、生长发育、胰岛素水平、消化及代谢酶、能量代谢水平等内因以及碳水化合物的种类、含量、摄食频率、环境温度等外因。本文综述了该领域的研究进展,并从能量代谢的角度对影响鱼类利用碳水化合物的因素及其机制进行了探讨,认为鱼类对碳水化合物的利用能力差与其维持生命活动的能耗功率水平相对应:鱼类(尤其是肉食性鱼类)代谢率较低,而以葡萄糖为底物代谢供能速率较高,因此摄入大量碳水化合物后可能导致供能速率过剩,以血糖的形式在体内堆积,表现为持续的高血糖现象。碳水化合物类型、摄食频率及水温对鱼类利用碳水化合物的影响均可能与此相关。     

鱼类的葡萄糖感知与糖代谢调节研究进展

为加深对鱼类糖的感知与代谢调控的认识,本文综述了鱼类的葡萄糖感知与摄食调控、糖代谢调控等领域的研究进展。鱼类的下丘脑不仅是中枢葡萄糖感受器所处的主要部位,同时也是食欲调节中枢。leptin、ghrelin、CCK、NPY等内分泌因子均能调控鱼类对糖的感知与摄食。另一方面,鱼类糖代谢受到胰岛素、GLP-1、ghrelin、CCK、NPY、SS等内分泌因子和糖、脂、蛋白质等营养素的双重调节。尽管鱼类对糖的利用能力低于陆生动物,但鱼体内亦存在较完善的糖的感知、摄食与代谢调节机制。因此,将来的重点工作应在于研究鱼类中枢神经系统整合营养和内分泌等信号的机制,研究草食性鱼类、杂食性鱼类在糖耐受力及糖异生调控机制上与肉食性鱼类存在的差异。     

鱼类线粒体代谢研究概况

鱼类是脊椎动物门中最原始的,同时也是种类最多的一个纲。线粒体中电子传递的作用是使ADP磷酸化成ATP。概述了鱼类线粒体代谢的研究近况,为人们认识和深人研究鱼类线粒体代谢提供基础资料。组织、细胞和亚细胞水平的能量代谢是能量学研究的重要内容之一,而线粒体代谢研究是其重要组成部分。细胞内物质的能量代谢主要发生在线粒体呼吸链上,通过氧化磷酸化作用将其能量转化为能量通货ATP。而鱼类不但种类多,而且原始,是进行脊椎动物线粒体代谢研究的模式动物之一。     

鱼类的摄食感觉

鱼类的摄食感觉是决定鱼类摄取食物与否的关键,也是鱼类营养学研究的基础.文章简要介绍了鱼类的摄食感觉器官--嗅觉、味觉、侧线、视觉的结构和功能,不同感觉器官在鱼类摄食过程中的作用以及不同感觉器官的反应在摄食过程中的关系.     

鱼类肥胖基因及脂肪蓄积调控机理研究

讨论了鱼类肥胖基因及脂肪蓄积词控机理研究现状，认为目前该领域不应完全拘泥于前途渺茫的鱼类肥胖基因克隆，而应从直接词控鱼类摄食与脂肪蓄积的关键功能基因人手，研究其表达词控相互关系．特别是摄食与脂肪蓄积基因调控之间是否存在偶联，从功能上确定有无鱼类肥胖基因存在，为下一步通过功能基因组手段获取可能存在的具重大知识产权价值的鱼类肥胖基因奠定必要基础。     

海洋鱼类摄食生态与食物网研究进展

首先总结归纳了海洋鱼类摄食生态与食物网研究中的实验方法,主要包括胃含物分析法、碳氮稳定同位素法、特定化合物同位素法等实验方法的发展历史和应用现状；随后介绍了海洋鱼类摄食生态与食物网最新研究进展和取得的成绩,主要包括海洋鱼类摄食生态中食物组成、摄食方式、摄食量和食物用于机体各种生命活动分配方式,以及海洋食物网研究中以传统胃含物分析法为基础、以简化食物网为核心,碳氮稳定同位素技术和生态系统模型的应用发展；最后,着重分析了我国海洋鱼类摄食生态和食物网研究中有待解决的问题,并对该领域今后的发展趋势进行了展望。     

鱼类的摄食行为与诱食剂

<正>摄食活动是所有生命活动的基础,通过摄食,生物获得能量与物质,使种群得以繁衍生息。鱼类由于终身生活在水体中,因此它的摄食行为与陆生动物相比,既有共通性又有其特殊性。     

珠江下游7种典型鲤科鱼类摄食器官形态特征比较

为探究鲤科鱼类的摄食器官形态差异, 以珠江下游的海南鲌(Culter recurviceps)、鲤(Cyprinus carpio)、广东鲂(Megalobrama terminalis)、赤眼鳟(Squaliobarbus curriculus)、草鱼(Ctenopharyngodon idellus)、鲮(Cirrhinus molitorella)和鲢(Hypophthalmichthys molitrix) 7 种典型鲤科鱼类为研究对象, 基于形态解剖和多元分析等方法, 比较了这 7 种鱼类外部和内部摄食器官形态的特征差异。结果显示, 7 种鲤科鱼类外部摄食器官形态的种间差异主要体现在口裂宽、口裂高等与食物捕获有关的性状上, 内部摄食器官形态的种间差异主要体现在咽骨长、咽骨后肢长等与食物咀嚼有关的性状上, 内部摄食器官形态分化程度显著大于外部摄食器官。另外, 研究发现食性对鲤科鱼类内部摄食器官形态影响大于系统发育地位的影响, 外部摄食器官形态性状对于鱼类分类具有重要的参考价值。 本研究揭示了同域分布鲤科鱼类的摄食器官结构差异, 探讨了摄食器官形态结构与食性、系统演化地位的关系, 对于了解鲤科鱼类生态适应机制以及开展珠江鱼类资源保护具有重要意义。     

真鲷幼鱼能源物质的研究↑（*）

鱼类能源物质的研究是鱼类能量代谢研究的重要组成部份。日本学者采用封闭、半封闭、流水方式，研究了体重在００００２～２７０ｇ间的真鲷（Ｃｈｒｙｓｏｐｈｒｙｓｍａｊｏｒ）在２０℃条件下的耗氧率与体重之间的关系〔８〕。然而，关于真鲷能量代谢的研究还未见报道...     

鱼类诱食剂研究进展

1引言 水产诱食剂就是能将鱼类吸引至饵料周围和引起鱼类食欲并促进其完成吞食饵料过程的物质。这种物质包括鱼类摄饵引诱物质和摄饵刺激物质。诱食剂在改善饲料的诱食性、适口性和饲料转化率等方面都起到重要的作用，一方面诱食剂可以通过特殊气味掩盖饲料中的不良气味，刺激鱼虾的感觉器官，以达到促进鱼虾摄食、加快鱼虾生长的目的；另一方面，通过诱食剂诱导鱼虾摄食，缩短了摄食时间，可以减少水体中的残饵和饲料的溶失，在提高饲料利用率的同时，也减少了饲料对水体的污染。     

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.