DNA 条形码在鲱形目鱼类物种鉴定和系统进化分析中的应用

采用PCR特异性扩增获得中国近海鲱形目(Clupeiformes)2科6属7种的48条线粒体COI基因序列,结合从Gen Bank筛选出的4科40属83种的COI基因序列225条,对鲱形目鱼类的COI条形码基因特征、种内与种间遗传距离及其分子系统进化关系进行了分析,探索了DNA条形码技术在辅助鱼类物种鉴定和分类中的适应性。结果表明,4科41属90种273条COI基因序列的平均碱基组成为T:28.3%、C:28.3%、A:24.2%、G:19.2%,碱基组成表现出明显偏倚性。鲱形目鱼类种间的平均遗传距离为0.131,种内平均遗传距离为0.003,种间距离为种内距离的41倍;系统学分析结果显示,97.8%的鱼类在系统进化树上均为单系。可见,鲱形目鱼类DNA条形码符合物种鉴定的要求,且基于COI基因所建的NJ树对物种分类具有较为准确的辨识力。系统进化分析结果表明,COI基因不仅能够解决低阶分类单元的系统进化关系,对于高阶分类单元的系统分析研究结果也有一定参考价值。     

基于线粒体COI的DNA条形码在对虾科种类鉴定中的研究

对虾科(Penaeidae)包含有26个属,约有200多种对虾,由于同属内的对虾在形态上非常相似,只呈现细微的差别,因此使得只基于形态学对对虾科物种的鉴别非常困难。为确定DNA条形码技术在对虾科物种鉴别的可行性,在本研究中,我们采用线粒体细胞色素c氧化酶亚基I(COI)基因研究了32种对虾的核苷酸组成、对虾种间及种内遗传距离,用邻接法(Neighbor-joining)构建32种对虾COI基因序列系统发生树。结果表明,对虾COI基因组成偏倚明显,A+T含量(61.5%)显著高于G+C(38.5%)。基于Kimura双参数模型计算,32个物种的种内平均遗传距离为0.003,种间平均遗传距离(0.468)是种内遗传距离的156倍,符合Hebert提出的种间遗传距离大于或等于10倍种内遗传距离的标准。在系统进化树中,32种对虾中有30种对虾都以较高的置信度聚合成独立的分支。可见,线粒体COI基因作为对虾科DNA条形码在物种的鉴别上具有很好的应用性,可以作为形态学分类系统的必要补充和佐证。     

基于线粒体COI的DNA条形码在对虾科种类鉴定中的研究

对虾科(Penaeidae)包含有26个属,约有200多种对虾,由于同属内的对虾在形态上非常相似,只呈现细微的差别,因此使得只基于形态学对对虾科物种的鉴别非常困难。为确定DNA条形码技术在对虾科物种鉴别的可行性,在本研究中,我们采用线粒体细胞色素c氧化酶亚基I(COI)基因研究了32种对虾的核苷酸组成、对虾种间及种内遗传距离,用邻接法(Neighbor-joining)构建32种对虾COI基因序列系统发生树。结果表明,对虾COI基因组成偏倚明显,A+T含量(61.5%)显著高于G+C(38.5%)。基于Kimura双参数模型计算,32个物种的种内平均遗传距离为0.003,种间平均遗传距离(0.468)是种内遗传距离的156倍,符合Hebert提出的种间遗传距离大于或等于10倍种内遗传距离的标准。在系统进化树中,32种对虾中有30种对虾都以较高的置信度聚合成独立的分支。可见,线粒体COI基因作为对虾科DNA条形码在物种的鉴别上具有很好的应用性,可以作为形态学分类系统的必要补充和佐证。     

基于线粒体COI的DNA条形码在对虾科种类鉴定中的研究

对虾科(Penaeidae)包含有26个属,约有200多种对虾,由于同属内的对虾在形态上非常相似,只呈现细微的差别,因此使得只基于形态学对对虾科物种的鉴别非常困难。为确定DNA条形码技术在对虾科物种鉴别的可行性,在本研究中,我们采用线粒体细胞色素c氧化酶亚基I(COI)基因研究了32种对虾的核苷酸组成、对虾种间及种内遗传距离,用邻接法(Neighbor-joining)构建32种对虾COI基因序列系统发生树。结果表明,对虾COI基因组成偏倚明显,A+T含量(61.5%)显著高于G+C(38.5%)。基于Kimura双参数模型计算,32个物种的种内平均遗传距离为0.003,种间平均遗传距离(0.468)是种内遗传距离的156倍,符合Hebert提出的种间遗传距离大于或等于10倍种内遗传距离的标准。在系统进化树中,32种对虾中有30种对虾都以较高的置信度聚合成独立的分支。可见,线粒体COI基因作为对虾科DNA条形码在物种的鉴别上具有很好的应用性,可以作为形态学分类系统的必要补充和佐证。     

线粒体COI基因条形码在鲿科鱼类物种鉴定中的应用

为了探讨线粒体COI基因作为DNA条形码在中国鲿科(Bagridae)鱼类物种鉴定中的有效性,以及系统发育中的适用性,本研究对4属11种鲿科鱼类进行PCR扩增,获得48条线粒体COI基因序列,同时从Gen Bank筛选获得8种鲿科鱼类的12条COI基因序列进行分析。19种鲿科鱼类的COI基因序列特征显示:长度为674 bp的COI序列片段平均碱基组成为24.82%A,30.44%T,27.10%C和17.64%G,碱基组成呈现明显的AT偏倚性(55.26%),具有硬骨鱼类的线粒体COI基因的碱基组成的典型特征。核苷酸位点中有变异位点226个,简约信息位点195个,单一信息位点31个,转换颠换比为3.35。19种鲿科鱼类的种内、种间和属间平均遗传距离分别为0.0041、0.1136和0.1268,种间遗传距离平均为种内遗传距离的27.7倍。在本研究中,鲿科鱼类所有的物种均形成单系,在物种鉴别上与形态学分类结果基本一致,然而鲿科的4个属中只有鱯属形成单系,黄颡鱼属、属和拟鲿属均未形成单系,其进化地位需要进一步研究。线粒体COI基因作为条形码可有效对鲿科鱼类进行物种鉴定,也为鲿科的系统发育提供了参考。     

基于线粒体COI的DNA条形码在对虾科种类鉴定中的研究

对虾科(Penaeidae)包含有26个属,约有200多种对虾,由于同属内的对虾在形态上非常相似,只呈现细微的差别,因此使得只基于形态学对对虾科物种的鉴别非常困难。为确定DNA条形码技术在对虾科物种鉴别的可行性,在本研究中,我们采用线粒体细胞色素c氧化酶亚基I(COI)基因研究了32种对虾的核苷酸组成、对虾种间及种内遗传距离,用邻接法(Neighbor-joining)构建32种对虾COI基因序列系统发生树。结果表明,对虾COI基因组成偏倚明显,A+T含量(61.5%)显著高于G+C(38.5%)。基于Kimura双参数模型计算,32个物种的种内平均遗传距离为0.003,种间平均遗传距离(0.468)是种内遗传距离的156倍,符合Hebert提出的种间遗传距离大于或等于10倍种内遗传距离的标准。在系统进化树中,32种对虾中有30种对虾都以较高的置信度聚合成独立的分支。可见,线粒体COI基因作为对虾科DNA条形码在物种的鉴别上具有很好的应用性,可以作为形态学分类系统的必要补充和佐证。     

基于线粒体COI序列的DNA条形码在中国海口足类物种鉴定中的应用分析

中国海口足类动物区系具有丰富的物种多样性,是我国海洋底栖生物中的重要经济类群。口足类的属内种间鉴别特征有的极为相似,仅依靠传统的形态分类方法很难对近缘种和疑难种进行准确的鉴定。DNA条形码技术可以弥补传统形态学鉴定的某些局限,为物种鉴定提供了有效的工具。该研究探讨了利用线粒体COI序列对中国海口足类进行物种鉴定的可行性,共获得口足目4总科6科24属38个种的204条线粒体COI序列,与Gen Bank收录的14种42条口足类同源序列进行比对,结果显示口足类COI基因不存在碱基插入缺失现象,碱基组成偏倚明显,A+T含量(63.5%)显著高于G+C含量(36.5%)。基于Kimura双参数模型计算遗传距离,结果显示遗传距离随着分类阶元的增高而增大。同物种种内个体间的遗传距离变化范围在0%~3.91%,平均值为0.76%。同属内各物种间的遗传距离变化范围为6.55%~18.99%,平均值为12.91%。同科内不同属间的遗传距离变化范围为9.16%~23.32%,平均值为16.89%。不同科间的遗传距离变化范围为16.52%~26.6%,平均值为21.31%。由此可见,口足类COI基因的种间和种内遗传距离存在明显的间隙。基于COI序列构建的口足类邻接关系树显示所有包含大于1个个体的物种均可形成单系群,且节点支持率均为100%。本研究证明了COI序列作为DNA条形码标准基因在口足类物种鉴定中的有效性。此外,研究发现中国沿海分布的口虾蛄可能至少存在两个隐存种,实证了基于COI序列的DNA条形码技术能够用于口虾蛄隐存多样性的探究。     

基于COI和16S rRNA的库页岛马珂蛤遗传多样性和分子系统进化研究

本研究以库页岛马珂蛤(Pseudocardium sachalinense)为研究对象,讨论COI和16S rRNA两种DNA条形码在贝类的遗传多样性、分子进化和种类鉴定的适用性,并利用两种条形码评估库页岛马珂蛤的遗传多样性。本文在获得库页岛马珂蛤线粒体全基因组的基础上,测序获得库页岛马珂蛤群体的COI和16S rRNA序列,发现COI基因核苷酸多样性为0.00195,高于16S rRNA核苷酸多样性(0.00073)。基于COI基因的单倍型多样性为0.76,大于16S rRNA的单倍型多样性(0.318)。其次,用全线粒体基因组构建8种贝类的系统进化树为参考,发现基于COI和16S rRNA的系统进化树与参考一致,提示这两种条形码片段可用于推断贝类的分子进化关系。最后,分别对马珂蛤科和帘蛤科15属17种贝类的COI基因和16Sr DNA进行序列比较,发现COI基因和16S rRNA的种间遗传距离均是种内距离的62倍。以上结果说明,16S rRNA与COI基因一样,能有效地构建马珂蛤科和帘蛤科的系统发育关系和物种鉴定,但在分析库页岛马珂蛤的遗传多样性时利用COI基因比16S rRNA能发现更多的遗传变异。     

不同DNA条形码基因在帘蛤目贝类分类鉴定中的比较分析

DNA条形码基因已经广泛应用在海洋贝类的分类鉴定、系统发育进化、种群遗传分析等领域的研究。为进一步研究评估不同DNA条形码基因在海洋贝类鉴定中的作用,本研究利用从Gen Bank数据库随机下载的帘蛤目COI、16S r RNA、18S r RNA和28S r RNA基因序列,通过传统距离法和单系聚类法结合分析,比较了上述DNA条形码基因在鉴定物种及系统发育进化中的鉴定效率,并以本实验室已获得的部分贝类DNA序列进行了验证。结果表明,根据"10倍法则"和"2%"阈值标准,本研究中COI能够鉴定57.1%物种,16S r RNA能够鉴定60.9%,18S r RNA鉴定16.7%,而28S r RNA无法有效鉴定;多数种COI和16S r RNA基因序列的种间遗传距离和种内遗传距离存在"条形码间隙",而18S r RNA和28S r RNA序列的种间和种内的遗传距离存在显著重叠,没有明显"条形码间隙";聚类分析结果表明,基于COI基因序列,87.9%的个体与同种聚为单系,以16S r RNA序列,65.6%的个体与同种聚为单系,未聚成单系的个体则形成姐妹系,未出现不同种聚为单系现象,能够呈现与形态分类基本一致的系统发生关系;但18S r RNA和28S r RNA呈现的聚类关系相对混乱。相对而言,在鉴定帘蛤目物种时,COI和16S r RNA都能够作为条形码基因,且COI有效性更高,18S r RNA和28S r RNA基因由于种内变异较大,不适于作为条码基因。研究结果为科学选用DNA条形码基因进行帘蛤目贝类的鉴定提供了参考资料。     

山东近海习见鱼类DNA条形码及其电子芯片分析

从GenBank下载到13目50科73属77种山东近海鱼类的线粒体细胞色素c氧化酶I(CO I)序列,通过分析其遗传距离及系统进化,并基于CO I序列筛选物种特异性探针来分析DNA芯片技术在进行物种鉴定时的可行性。结果表明,在CO I基因DNA条形码的分析中,77种鱼类的种间遗传距离(平均0.117)明显大于种内遗传距离(平均0.0034),且每个物种的不同个体在进化树上都能聚在一起,提示DNA条形码能全部区分77个物种;根据CO I基因设计的用于芯片的特异性探针中,77个物种最终有64个可以筛选出物种特异性探针,占总物种数的83.1%,本研究旨在为山东近海鱼类物种鉴定提供了技术支持。     

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.