外排泵抑制剂对海水养殖源弧菌酰胺醇类药物耐药性的影响

通过检测从海水养殖中分离的对氟苯尼考低敏感弧菌菌株中常见酰胺醇耐药基因的携带情况,来分析外排泵抑制剂对弧菌酰胺醇耐药性的影响,旨在研究主动外排机制在我国海水养殖源弧菌耐药中的作用。本研究从前期分离的海水养殖源弧菌中挑选出41株对氟苯尼考低敏感的菌株,运用琼脂稀释法测定了这些菌株对酰胺醇类药物(氯霉素和氟苯尼考)的敏感性;利用PCR方法检测了这些菌株的酰胺醇外排泵耐药基因和整合子的携带情况,包括外排泵基因floR、cmlA、pexA、fexA、fexB和optrA,以及Int1、SXT和ISCR1整合子相关基因;同时研究4种外排泵抑制剂对弧菌氯霉素、氟苯尼考最小抑菌浓度(MIC)的影响,利用琼脂稀释法检测41株弧菌分别加入甲基吡咯烷酮(N-methyl-2-pyrrolidone,NMP)、利血平(reserpine)、羰基氰氯苯腙(carbonyl cyanide m-chlorophenyl hydrazone,CCCP)和苯丙氨酸-精氨酸-β萘酰胺(Phe-Arg-β-naphthylamide,PAβN)4种外排泵抑制剂前后对氯霉素和氟苯尼考的MIC值的变化情况。副溶血弧菌(14株)、溶藻弧菌(17株)、哈维氏弧菌(8株)、创伤弧菌(2株)共41株氟苯尼考低敏感弧菌敏感度检测结果显示,氟苯尼考耐药菌株39株、氯霉素耐药菌株11株。41株氟苯尼考低敏感弧菌菌株中,酰胺醇类外排泵基因floR检出率为100%,而cmlA的检出率仅为17.1%,其他4个外排泵基因均未检出;整合子相关基因Int1、SXT和ISCR1的检出率分别为46.3%(19/41)、46.3%(19/41)和63.4%(26/41)。41株弧菌中,添加NMP、利血平、CCCP和PAβN后,分别有0株、2株、10株和2株弧菌为氯霉素外排阳性菌;分别有1株、1株、15株和3株弧菌为氟苯尼考外排阳性菌。研究表明,CCCP被验证可以作为有效治疗酰胺醇类药物耐药弧菌的外排泵抑制剂。     

养殖刺参溃疡病病原菌RH2的鉴定及其生物学特性分析

从患溃疡病养殖刺参(Apostichopus japonicus)病灶处分离出3株优势菌(RH1、RH2、RH3),以浸浴、体腔注射、体壁肌肉注射等方式进行感染实验,证实菌株RH2为养殖刺参溃疡病的病原菌,其对刺参的LD50(半数致死量)每尾为5.68×106CFU,并证实浸浴、体腔注射的方式无法感染刺参,该菌可能通过体表创伤侵入的方式感染刺参。经形态学观察、生理生化特性分析、16SrRNA和HSP60基因测序确定菌株RH2为溶藻弧菌(Vibrio alginolyticus)。基于16S rRNA基因构建的系统发育树显示,菌株RH2与溶藻弧菌(AF513447)亲缘关系最近,置信度为50%;HSP60基因序列分析表明RH2与溶藻弧菌(AY332570、AF230931)聚为一个分支,且置信度高达99%。菌株RH2的最适生长盐度为25~35,最适生长pH为7.2~8.0,最适生长温度为14~22℃。对18种药物的敏感实验证实菌株RH2对诺氟沙星、复方新诺明、壮观霉素等较为敏感。     

3株O3血清型鳗弧菌灭活疫苗的免疫原性和免疫保护效果

鳗弧菌(Vibrio anguillarum)O3血清型菌株是感染鱼类的重要病原菌,本文研究了3株O3血清型鳗弧菌(SMP1、SMP3和SMP4)灭活疫苗的免疫原性和免疫保护。首先在牙鲆(Paralichthys olivaceus)体内对3株鳗弧菌进行复壮;检测复壮后的菌株毒力,检测的3株鳗弧菌对蓝蔓龙(Trichogaser trichopterus)的半数致死量(LD50)分别为105.1 CFU/ml(SMP1)、104.7 CFU/ml(SMP3)和105.4 CFU/ml(SMP4);制备了3株菌的甲醛灭活疫苗,注射免疫牙鲆,免疫后第7天可检测到牙鲆的血清特异性抗体产生,免疫后第28天的血清特异性抗体效价为1:1280(SMP1)、1:640(SMP3)和1:905(SMP4),提供的免疫保护率(Relative percent survival rate,RPS)为94.4%(SMP1)、100%(SMP3)和73.7%(SMP4)。研究表明,3株致病性O3血清型鳗弧菌菌株具有良好的免疫原性,其中SMP3为最适疫苗候选株。本研究为鳗弧菌O3血清型疫苗的开发应用奠定了基础。     

抗弧菌光合细菌的分离鉴定及对氨氮和亚硝态氮的降解特性

该研究采用双层平板涂布法和划线法,从不同地区的海洋环境样品中分离纯化光合细菌,以副溶血弧菌(Vibrio parahemolyticus)、创伤弧菌(V.vulnificus)、鳗弧菌(V.anguillarum)为指示菌,采用牛津杯法测定海洋光合细菌菌株的抑菌作用,采用靛酚蓝分光光度法和盐酸萘乙二胺分光光度法测定不同菌株对氨氮(NH_4~+-N)和亚硝态氮(NO_2~--N)的降解作用,筛选出具有抗弧菌并高效降解NH_4~+-N和NO_2~--N复合功能的优良菌株。结果显示,从30个海水、海泥等样品中分离得到3株光合细菌,分离自连云港车牛山岛海水样品的菌株P-3,对3种弧菌均具有较强的抑制作用,其中对鳗弧菌的作用最强,抑菌圈直径为5.3 mm。3株光合细菌均具有一定的降解NH_4~+-N和NO_2~--N作用,菌株P-3的降解作用最强,在含有50 mg·L~(-1) NH_4~+-N和NO_2~--N的培养基中培养4 d,降解率分别为89.68%和94.98%。经形态学观察、生理生化试验和16S rDNA序列分析,确定P-3为沼泽红假单胞菌(Rhodopseudomonas palustris)。     

抗弧菌海洋细菌的分离筛选及其抗菌作用测定

采集连云港海域海水、海泥以及海洋动植物等样品86个,分离到海洋细菌176株.以病原性弧菌鳗弧菌为指示菌,采用平板对峙法在2216E培养基上测定不同海洋细菌菌株的抗菌作用, 其中XDY-7-4、YC-6-3、BM-1、BN-1、BN-2和XS1-5等6个海洋细菌菌株有明显的抗菌作用,菌株BN-1的抑菌带为11.2 mm,抗菌作用最强;其次为菌株XS1-5 、XDY-7-4 和YC-6-3,抑菌带宽度为10.4、10.2、9.9 mm;菌株BN-2和BM-1对鳗弧菌的抑菌作用较弱. 采用打孔法测定不同海洋细菌菌株无菌发酵液的抗菌作用,结果表明,菌株BN-1对鳗弧菌生长的抑制作用最明显,其次为菌株YC-6-3和XDY-7-4,菌株BM-1、XS1-5和BN-2的抗菌效果较弱.     

对虾养殖池中一株弧菌拮抗菌的分离鉴定

从对虾养殖池中分离出1株编号为2013082515(简称菌株15)的菌株,以鳗弧菌(Vibrio anguillarum)、哈维氏弧菌(Vibrio harveyi)和副溶血弧菌(Vibrio parahaemolyticus)为指示菌,分析了菌株15对指示菌的抑菌效果及最低抑菌浓度,同时,分析了菌株15对其他7株弧菌的抑菌效果.结果显示,菌株15对3株指示菌均具有抑菌效果,对鳗弧菌、哈维氏弧菌及副溶血弧菌的最低抑菌浓度分别为2.50×104、2.50×105、2.50×105 CFU/ml;对其他弧菌也具有一定的抑菌效果.采用注射及浸泡感染方法分析了菌株15对对虾的生物安全性,结果显示,在高浓度时,菌株15对对虾具有潜在毒性.分别用细菌全细胞脂肪酸气相色谱法和16S rDNA序列分析比对法对该菌进行分类鉴定,表明菌株15为一株假交替单胞菌(Pseudoalteromonas sp.).     

2株副溶血弧菌不同盐度下致病性和毒力基因差异分析

副溶血弧菌(Vibrio parahaemolyticus)是常见的食源性致病菌和海水养殖动物致病菌,目前已知的毒力基因有tlh、tdh、trh、T3SS、pirA、pirB、toxR/S、orf8等。盐度是影响细菌基因表达的关键生态因子之一,为进一步探求副溶血弧菌的致病机理,对2株分别分离自海水和淡水养殖发病凡纳滨对虾(Litopenaeus vannamei)中的副溶血弧菌在不同盐度下的生长速率、致病性进行检测,并用q-PCR方法对菌株毒力基因携带和表达情况进行定量研究。实验结果表明:海水菌株383生长速率快于淡水菌株V9,但菌株383在生长稳定期的细菌浓度明显低于菌株V9;菌株383对凡纳滨对虾的致病性明显高于菌株V9,前者的48 h半致死浓度(LD_(50))低于后者2个数量级;2株副溶血弧菌皆携带毒力基因tlh、T3SS1和pirA/B,但未检测到tdh、trh、T3SS2、toxR/S和orf8。部分毒力基因表达量检测结果显示,菌株383和菌株V9均为vcrD1表达量最高,其次是pirA,vopD1表达量最低;4个毒力基因不仅在2菌株间的表达量差别较大,而且盐度对同一菌株不同毒力基因表达的影响也是不同的。2株副溶血弧菌的毒力与pirA和vcrD1的表达量呈正相关性。研究结果为探究环境因素与副溶血弧菌致病力的关系提供了科学依据,同时也提示,淡水养殖凡纳滨对虾要防范副溶血弧菌输入的风险。     

牙鲆秦皇岛弧菌HQ010712-1外膜蛋白及其抗原性分析

采用十二烷基肌氨酸钠(Sarkosyl)和苯甲基磺酰氟(PMSF)2种方法提取秦皇岛弧菌HQ010712-1(Vibrio qinhuangdaora sp.nov.)外膜蛋白,结果显示 Sarkosyl法提取效果较好,且所提取的主要外膜蛋白分子量为102kD、45 kD、39 kD、36 kD、30 kD、28 kD、24 kD、22 kD;为比较该菌株与弧菌属其他细菌外膜蛋白组分及抗原性异同,以鳗弧菌(Vibrio anguillarum)、副溶血弧菌(Vibrio parahaemolyticus)、溶藻胶弧菌(Vibrio alginolyticus)为对照,电泳图谱显示4种弧菌外膜蛋白的分子量主要集中在22～48 kD之间;利用抗秦皇岛弧菌HQ010712-1血清的免疫印迹表明菌株HQ010712-1外膜蛋白中分子量为45 kD、36 kD的蛋白条带呈现阳性反应,其他3种弧菌外膜蛋白中均有与该抗血清反应的条带,且分子量为36 kD的反应带为菌株HQ010712-1、副溶血弧菌、溶藻胶弧菌共有.本研究旨在为进一步筛选和研究致病性弧菌的共同保护性抗原提供参考.     

对虾源副溶血弧菌强毒株HNBX-1的分离鉴定与毒性分析

副溶血弧菌(Vibrio parahaemolyticus)是海水养殖中常见的条件致病菌,具有发生率高和流行面广等特点。本文从患红体病的凡纳滨对虾(Litopenaeus vannamei)体内分离得到一株细菌HNBX-1,经生化实验结合热休克蛋白60(Heat Shock Protein 60,HSP60)基因鉴定为副溶血弧菌。毒性实验表明,弧菌HNBX-1对凡纳滨对虾的毒性极强,感染24 h时的LD50为3.5×104cfu·mL-1;对其重要毒力基因———耐热溶血毒素基因(TDH)、耐热溶血毒素相关基因(TRH)和Ⅲ型分泌系统(T3SS1和T3SS2)的分析结果显示,HNBX-1中的TDH、TRH以及T3SS2基因检测结果均为阴性,而T3SS1的4个毒力基因中的VP1689(vscK)和VP1694(vscF)基因扩增为阳性,表明该副溶血弧菌菌株的强毒特性与其携带的T3SS1密切相关。     

蟹源拟态弧菌外毒素生物学特性研究

对蟹源拟态弧菌HX-4菌株外毒素的酶活性、溶血活性、细胞毒性和致死性等生物学特性进行了系统研究。采用固体硫酸铵盐析法和层析技术提取拟态弧菌HX-4菌株外毒素,所得外毒素具有酪蛋白酶、明胶蛋白酶、溶血素等多种毒性酶活性、细胞毒性(HEp-2)、肠毒性和致死性等生物学特性,TC ID50为0.025μg,对中华绒螯蟹的半数致死量(LD50)为1.40μg。     

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.     

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.