鱼类消化系统的结构、功能及消化酶的分布与特性

本文综述了鱼类消化系统的结构、功能及消化酶的分布与特性的研究进展，旨在进一步了解鱼类各个消化器官的结构以及分布，其中的主要酶类所产生的功能效应，为今后深入探讨鱼类摄食、消化和吸收的生理机制等研究提供参考。     

海水养殖鱼类消化酶研究进展

综述了海水养殖鱼类消化酶活性研究的以下三方面：（1）消化酶活性的研究,内容包括消化酶的活性分布,温度、pH、外界环境及季节变化对消化酶活性的影响;（2）不同生长阶段消化酶活性的变化,内容包括与仔鱼生长发育相对应的消化酶形成的时间,稚鱼、幼鱼在生长进程中,消化酶的变化规律;（3）鱼类的食物组成对消化酶活性的影响,内容包括饲料的种类和性质,以及饲料不同成分对鱼类消化酶的分泌、活性的影响,进而对饲料利用率的影响。本本对海水养殖鱼类消化酶的活性进行了较为系统的综述,为海水养殖鱼类饲料的开发提供参考数据。     

饲料对美国红鱼幼鱼蛋白酶活性的影响

消化酶活性是反映鱼类消化生理机能的一项重要指标，鱼类消化酶活性的高低决定鱼类对营养物质消化吸收的能力，从而决定鱼类生长发育的速度。国内外对鱼类消化酶进行了广泛研究，随着消化酶研究领域的深入，饲料与消化酶的关系也开始探讨。饲料对美国红鱼蛋白酶活性研究尚未见报道，本文对饲料与美国红鱼幼鱼蛋白酶活性的关系开展研究，以期为美国红鱼人工配合饲料的研究和养殖提供有价值的参考资料。     

样品处理对罗非鱼和银鲫肠道消化酶活性测定的影响

近年来,有关鱼类消化酶的研究报告不断增多,为鱼类消化生理的研究提供了大量有价值的实验资料。在鱼类消化酶的研究中,众多研究者采用了基本相近的研究方法[1-5],但有时却得出相矛盾的结果,这种现象似乎不能简单的归结为鱼类消化酶特性的多样性,而由实验方法和手段的差异导     

鱼类消化酶的研究进展

鱼类消化酶主要有蛋白酶、脂肪酶、纤维素酶和淀粉酶等几种，其活性随种类、生长阶段和健康状况以及外界环境的变化而变化，随着水产养殖业的发展，鱼类消化酶的研究日益受到人们的重视。通过对这些问题的研究，使人们对诸如鱼类消化能力的大小、饵料需求及配比、消化酶对饵料的适应等方面有了更加深入的了解，从而指导优化水产养殖业中的饵料问题，为水产养殖业开创一个全新的局面，这也是鱼类消化酶研究的实际意义所在。     

流速对吉富罗非鱼幼鱼行为和消化酶的影响

在不同流速条件下观测了吉富罗非鱼行为学和消化酶指标,结果发现随着流速的增大,罗非鱼的呼吸频率和摆尾频率显著增加,随着作用时间的延长,两种指标保持相对稳定。同一时间内不同流速下7d和30d取样的罗非鱼的蛋白酶、淀粉酶和脂肪酶随着流速的增加而增加,1d取样的酶活力变化不大。同一流速下,随着水流作用时间的延长,三种消化酶呈增加趋势。说明水流能增加鱼体的运动能力,而长时间的水流作用能增加鱼类三种消化酶的活力,促进消化和吸收。     

四种不同食性鱼类的消化酶活性及肠道组织形态学比较研究

为了探讨食性与鱼类消化酶分泌及肠道组织形态学的关系，通过比较分析滇池高背鲫(Carassius auratus)、草鱼(Ctenopharyngodon idellus)、鳜(Siniperca chuatsi)和昆明裂腹鱼(Shizothorax grahami)4种不同食性鱼类鱼体近似成分、血液生化指标、消化酶活性及肠道组织形态的差异。结果表明，鳜的全鱼水分显著低于其他鱼类，粗蛋白含量显著高于其他鱼类；谷草转氨酶GOT、白蛋白AIB、甘油三酯TG、总胆固醇TCH等部分血液生化指标受食性影响显著；鳜肠道蛋白酶显著高于草鱼，淀粉酶活性显著低于草鱼；鱼类肠道形态(绒毛高度、绒毛宽度和肌层厚度)与食性相关，如鳜肠道微绒毛分支较多，结构复杂。肠道结构的复杂性加大了食糜在肠道中的保留时间，促进了鱼类对营养物质的充分吸收。综上所述，食性与鱼类消化酶活性及肠道组织形态相适应，通过分析消化酶活性和肠道组织形态，有助于界定鱼类食性，改进饲料配方和饲养方法。     

生态因子对鱼类消化酶活力影响的研究进展

鱼类消化酶的活性大小与其所生活的水环境紧密相连,本文主要分析了生态因子如温度、盐度、pH和重金属离子,饵料(营养成份、含有的外源性酶以及量的多少)对鱼类消化酶活性影响的研究状况,为水产养殖中优化人工饲料和鱼类的健康养殖提供依据。     

pH影响暗纹东方魨蛋白酶活性的研究

鱼类消化酶的研究是鱼类消化生理的重要研究内容,也为配合饲料的研制提供依据,暗纹东方鲀,俗称河豚,是我国特有种类.随着人繁技术的成功,暗纹东方鲀也成了具有极高经济价值的特种水产养殖对象,因此对其消化酶的研究具有重要意义,消化酶活性与环境因素有密切关系,其中pH是主要影响因素.本文报道pH影响暗纹东方鲀蛋白酶活性的初步研究成果,期望对配合饲料的研制有所帮助.     

海水鱼类仔稚鱼消化生理学研究进展

综述了海水鱼类仔稚鱼消化系统的发育过程，讨论了消化系统中各种酶的分布以及各发育时期参与消化的酶的种类及其活性，分析了饵料与消化系统中酶的互动关系，以及外源性消化酶和神经肽在仔稚鱼消化过程中所起的作用。     

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.     

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.     

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.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

Effects of Spirulina platensis as a feed additive on growth and coloration of blue dolphin cichlids (Cyrtocara moorii Boulunger, 1902)

This study was carried out to investigate the effects of replacing fish meal with dietary Spirulina as a feed supplement on the growth performance and coloration of blue dolphin cichlids (Cyrtocara moorii). Five isonitrogenous (47% crude protein) and isocaloric (17.36 kJ/g digestible energy) diets were for formulated to replace FM with 0, 5, 10, 15 and 20% Spirulina (designated as Control, SP5, SP10, SP15 and SP20 respectively) and fed to the fish (initial body weight, 3.15 ± 0.01 g). Fish were randomly distributed into fifteen 120 L aquariums (26.5 ± 1.00°C), 15 fish per aquarium. The diets were tested in triplicate for 12 weeks. Experimental groups were fed twice daily (09:00 and 17:00) by hand to satiation. At the end of the feeding trial, significantly (p < 0.05) higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and lower feed conversion ratio (FCR) were observed in fish fed the SP10 diet when compared to the SP20 diet. There was no significant difference in these parameters between the other groups. The skin coloration of blue dolphin cichlid fed a diet containing Spirulina meal was enhanced. The best coloration was observed in the SP15 group. These impressions were objectively validated by chemical determinations of carotenoids extracted from fish skins and passed statistical tests of significance. The study findings show that Spirulina meal does not diminish growth rates except at very high levels.     

Dietary thiamin and pyridoxine requirements of fingerling Indian major carp,Cirrhinus mrigala (Hamilton)

Two experiments were conducted to quantify the dietary thiamin (experiment I) and pyridoxine (experiment II) requirements of fingerling Cirrhinus mrigala for 16 weeks. In experiment I, dietary thiamin requirement was determined by feeding seven casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) with graded levels of thiamin (0, 0.5, 1, 2, 4, 8 and 16 mg kg^?1 diet) to triplicate groups of fish (6.15 ± 0.37 cm; 1.89 ± 0.12 g). Fish fed diet with 2 mg kg^?1 thiamin had highest specific growth rate (SGR), protein retention (PR), RNA/DNA ratio, haemoglobin (Hb), haematocrit (Hct), RBCs and best feed conversion ratio (FCR). However, highest liver thiamin concentration was recorded in fish fed 4 mg thiamin kg^?1 diet. Broken‐line analysis of SGR, PR and liver thiamin concentrations exhibited the thiamin requirement in the range of 1.79–3.34 mg kg^?1 diet (0.096–0.179 μg thiamin kJ^?1 gross energy). In experiment II, six casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) containing graded levels of pyridoxine (0, 2, 4, 6, 8 and 10 mg kg^?1 diet) were fed to triplicate groups of fish (6.35 ± 0.37 cm; 1.97 ± 0.12 g). Fish fed diet containing 6 mg kg^?1 pyridoxine showed best SGR, FCR, PR, RNA/DNA ratio, Hb, Hct and RBCs, whereas maximum liver pyridoxine concentration was recorded in fish fed 8 mg kg^?1 dietary pyridoxine. Broken‐line analysis of SGR, PR and liver pyridoxine concentrations reflected the pyridoxine requirement from 5.63 to 8.61 mg kg^?1 diet. Data generated during this study would be useful in formulating thiamin‐ and pyridoxine‐balanced feeds for the intensive culture of this fish.     

Sea bream culture in Egypt; status, constraints and potential

Marine fish farming in Egypt began in 1976 with the culture of gilthead sea bream, (Sparus aurata) as this fish was notably adaptable to brackish and marine pond conditions. Today, marine fish and shrimp farms amount to about 19,000 ha, out of which 42% is already in production while the rest, i.e., 58% is still under construction. In 1997, cultured gilthead sea bream production of 2,250 tons made up 3% of the 75,000 tons total aquaculture catch. In polyculture, usually with the grey mullet and sea bass, gilthead sea bream contributed 440 kg ha^–1 to the total yield of 1,700 kg ha^–1 (26%) over a period of 16 months. For the same period, the yield of monoculture ponds averaged 100 kg ha^–1, while in marine cages, yields ranged from 4–10 kg m³. In 1996–1997, fry of 0.25–1 g and fingerlings 1–10 g with a total of 3 million, were collected from the wild and 1 million fry were produced in the three marine hatcheries out of the four existing ones. The development of sea bream culture in Egypt is now severely inhibited by the shortage of seeds and adequate feeds. Exports of both sea bream and sea bass, during 1994–1996 averaged 1,300 tons per year.     

A Minchinia mercenariae‐like parasite infects cockles Cerastoderma edule in Galicia (NW Spain)

The cockle Cerastoderma edule fishery has traditionally been the most important shellfish species in terms of biomass in Galicia (NW Spain). In the course of a survey of the histopathological conditions affecting this species in the Ria of Arousa, a haplosporidan parasite that had not been observed in Galicia was detected in one of the most productive cockle beds of Galicia. Uni‐ and binucleate cells and multinucleate plasmodia were observed in the connective tissue mainly in the digestive area, gills and gonad. The parasite showed low prevalence, and it was not associated with abnormal cockle mortality. Molecular identification showed that this parasite was closely related to the haplosporidan Minchinia mercenariae that had been reported infecting hard clams Mercenaria mercenaria from the Atlantic coast of the United States. The molecular characterization of its SSU rDNA region allowed obtaining a fragment of 1,796 bp showing 98% homology with M. mercenariae parasite. Phylogenetic analysis supported this identification as this parasite was clustered in the same clade as M. mercenariae from the United States and other M. mercenariae‐like sequences from the UK, with bootstrap value of 99%. The occurrence of M. mercenariae‐like parasites infecting molluscs outside the United States is confirmed.     

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.