海子湖春季浮游植物群落结构与环境因子相关性分析

2012年春季对长湖海子湖浮游植物群落结构及其主要水环境指标进行调查,同时运用典范对应分析方法 (CCA)对浮游植物与环境因子的关系进行分析。结果表明,海子湖共检测到浮游植物93种(含变种和变型),其中绿藻(Chlorophyta)最多,占46.76%,其次为硅藻(Bacillariophyta)和蓝藻(Cyanophyta),分别为22.65%和15.00%;浮游植物优势种共6种,其中小球藻(Chlorella vulgaris)优势度高达0.36;浮游植物丰度在86.21×105~410.12×105个/L,平均为232.85×105个/L。多样性指数为1.82~3.28,均匀度指数为0.40~0.63。根据浮游植物丰度水平、优势度以及群落多样性指数等生物学指标进行综合评价,海子湖处于重度富营养化状态。CCA分析表明,浮游植物空间分布主要受到硝酸盐氮、化学需氧量、叶绿素以及磷酸盐等环境因子的影响,主要影响因素为海子湖地形、人为干扰因素以及水动力学相关参数。     

桃山水库浮游植物群落结构及水质营养状态评价

2009年的枯水期（5月）和丰水期（7月）,在桃山水库对浮游植物结构群落和水质状况进行了调查研究,结合生物监测和理化监测手段,基于浮游植物优势度、丰度、优势度以及综合指数评价方法,对研究水库进行了生态评价。结果显示：（1）桃山水库浮游植物共有7门46属73种及变种,其中以绿藻为主,分别占44 %;（2）生物量在2.29-10.96 mg﹒L-1之间,丰度变幅在(38.76-124.44)×105 ind.﹒L-1之间;（3）枯水期优势种以硅藻为主,丰水期优势种以以蓝藻、绿藻为主;（4）综合营养指数为42.0-60.1。综合评价结果表明：桃山水库枯水期和丰水期水质营养状态为轻富营养化,化学需氧量是影响桃山水库浮游植物群落结构的主要环境因子。     

高州水库浮游植物群落结构及其与环境因子的关系

摘要：为掌握高州水库浮游植物群落结构变化规律及其与环境因子的关系,2011年4月至2012年3月对高州水库浮游植物群落周年动态进行调查和分析。结果表明：高州水库共鉴定浮游植物7门97种,库区浮游植物细胞密度年变化范围为7.8×105-9.72×106 cells/L;全年主要优势种为铜绿微囊藻（Microcystis aeruginosa）与梅尼小环藻（Cyclotella meneghiniana）。Shannon-Wiener多样性指数和均匀度指数分析结果显示,高州水库各区域属于中污染状态;CCA分析结果表明,氮磷营养盐是影响高州水库浮游植物群落分布的重要因子,温度、pH与CODMn对浮游植物群落分布也有一定程度的影响。     

大连近海水产养殖区中浮游植物群落结构及其与环境因子的关系

为研究大连近海水产养殖区中浮游植物群落结构及其与环境因子的关系,于2020年1月、4月、7月和10月对大连7个区市县沿海裙带菜（Undaria pinnatifida）、仿刺参（Apostichopus japonicus）、菲律宾蛤仔（Ruditapes philippinarum）、扇贝、牡蛎和对虾为主的重点海区设置10个采样点,同步监测调查浮游植物种类组成、生物量及其水质,并对浮游植物群落与水环境因子进行Pearson相关分析和典范排序分析（CCA）。调查结果共发现3门31属78种浮游植物,主要由硅藻组成,还有少量的甲藻和金藻,优势种共14种。浮游植物细胞丰度变化在7.82×104～22.00×104ind./L之间,多样性指数变化在1.51～3.32之间,均匀度指数变化范围在0.378～0.588之间。Pearson相关分析结果表明,浮游植物细胞丰度、硅藻细胞丰度和多样性指数与氨氮浓度呈一定负相关。典范排序分析（CCA）结果表明,水温、p H、溶解氧（DO）、亚硝酸盐、氨氮和硝酸盐含量是影响大连近海水产养殖区浮游植物优势种变化的主要环境因子。     

苏北运东水网区浮游植物群落结构特征及与环境因子关系

为研究苏北运东水网区浮游植物群落结构特征及其与环境因子之间的关系，于2016年3月至12月对苏北运东水网区19个采样点进行了季节性浮游植物群落调查和水质监测。结果表明，浮游植物共计鉴定出142种，隶属于7门、75属，以绿藻门和硅藻门的种类数偏多，其中绿藻门共29属、58种，硅藻门共22属、44种。春、冬季以硅藻门密度最大，分别为2.49×106个/L和 1.67×106个/L；夏、秋季以绿藻门密度最大，为1.57×106个/L和 1.34×106个/L；Margalef丰富度指数（R）、Shannon-Wiener多样性指数（H''）、Simpson多样性指数（D）和Pielou均匀度指数（J）均在夏季最大，分别为1.374、3.198、0.944和0.831，在冬季和春季相对较小；运东河网区内部水流变缓，河网外部水体流动性相对较好，浮游植物密度的监测结果显示，内部河流大于外部河流，但生物多样性指数为外部河流小于内部河流；运东片各季节的主要浮游植物优势物种共有20种，春、冬季主要为硅藻门和隐藻门，而夏、秋季则主要为绿藻门和硅藻门，其中梅尼小环藻（Cyclotella meneghiniana）、尖针杆藻（Synedra acus）和啮蚀隐藻（Cryptomonas erosa）为全年常有的优势种。藻类优势物种与环境因子的CCA分析表明，影响运东片四季浮游植物群落分布的环境影响因子存在差异，其中BOD5、TP、NH3-N和CODMn是关键的环境影响因子。     

黄洲河流域浮游植物的季节变化及其环境影响因子

为了解贵州白云岩喀斯特世界自然遗产地浮游植物群落结构及其与环境因子的关系,于2017年秋季(10月)、2018年冬季（1月）、2018年春季（4月）、2018年夏季（8月）对遗产地境内黄洲河流域的浮游植物群落种类组成、优势种、丰度以及多样性的时空变化进行研究,并应用Pearson相关性分析和冗余分析（RDA）探究环境因子总氮（TN）、氨氮（NH3-N）、总磷（TP）、叶绿素a（Chl-a）、溶解氧（DO）、高锰酸盐指数（CODMn）、水温（WT）对黄洲河浮游植物群落结构的影响。结果表明,调查共鉴定出藻类6门、29科、37属、38种,以硅藻门和绿藻门居多。按季节划分,黄洲河流域优势种共9种,其中硅藻门5种,?绿藻门1种,?蓝藻门3?种;按空间划分,黄洲河流域优势种共19种,其中硅藻门9种,绿藻门4种,蓝藻门6种。浮游植物年均丰度为36.45×104个/L,夏季的丰度最高,达到89.7×104个/L,春秋季次之,冬季最低,仅8.9×104个/L。全年Margalef丰富度指数（D）、Shannon多样性指数（H）及Pielou均匀度指数（J）分别为0.34 ~0.51、1.18~1.4及0.72~0.84。Pearson相关性分析和冗余分析(RDA) 表明,影响遗产地浮游植物丰度和分布的主要环境因子为WT、CODMn、Chl-a。     

青岛崂山近岸海域浮游植物群落结构及其与环境因子的关系

2012年5月和8月对崂山近岸和流清河湾网箱增养殖区的浮游植物进行调查。结果显示,5月共检出浮游植物23属36种,细胞丰度变动范围为85.26×103～720.16×103cell/m3,夜光藻为优势种,数量占浮游植物总量的80%以上,受其影响,群落多样性较差,细胞丰度低。8月共检出浮游植物30属54种,细胞丰度变动范围为43.00×103～1 116.27×103cell/m3,群落多样性较好,细胞丰度较低。对浮游植物群落进行聚类分析,5月相似性在60%以上,8月在50%以上。崂山近岸的浮游植物细胞丰度平均值均大于流清河湾网箱增养殖区,而多样性均值前者均小于后者;相关性分析显示,细胞丰度平均值与N/P均值呈显著负相关(r=-0.81,P<0.05),而多样性均值与其呈显著正相关(r=0.98,P<0.05),认为影响浮游植物细胞丰度和多样性的最关键限制因子是无机氮。     

京杭运河苏北段秋冬季浮游植物群落结构特征及其与 环境因子的关系

在京杭运河苏北段秋冬两季开展水环境监测和浮游植物调查,为京杭运河苏北段的水生态环境保护提供参考。2020 年 10 月（秋季）和 2021 年 1 月（冬季）,对京杭运河苏北段布设的 16 个采样点开展了系统的水环境和浮游植物调查,根据Shannon-Wiener 多样性指数、 Pielou 均匀度指数和浮游植物细胞丰度进行了水质及水体营养状态的评价,利用 Pearson 相关性分析明确了浮游植物与环境因子的关系。结果显示：京杭运河苏北段秋冬季共采集到浮游植物 8 门 101 种,其中秋季 7 门 52 种、冬季 5 门 63 种,秋冬季均是以绿藻门和硅藻门为主,2个门类的种类数在秋冬季浮游植物种类总数的占比分别达到了 73% 和 82%;秋季浮游植物细胞丰度均值为 49.1×104 个/L,生物量均值为 0.344 mg/L,冬季浮游植物细胞丰度均值为 15.0×104 个/L,生物量均值为 0.193 mg/L;秋冬季浮游植物优势种主要以硅藻门（Bacillariophyta）和绿藻门（Chlorophyta）为主;秋季浮游植物的多样性评价结果优于冬季,秋冬季水体营养状态均为中营养型,相关性分析表明氮对京杭运河苏北段浮游植物群落结构的影响大于磷;另外,行船引起的水体扰动也是造成浮游植物群落差异的重要因素。     

金沙江下游浮游植物群落生态特征及与环境因子关系

为探究金沙江下游干流江段浮游植物群落特征及物种与生境之间的关系，于2019年6月和10月对金沙江下游攀枝花至水富段因梯级电站蓄水产生的三类不同水体（自然河流型、过渡型、类湖泊型）开展浮游植物与水环境调查，结果显示：2次调查共鉴定出浮游植物7门53属74种，主要以硅藻（47.30%）、绿藻（33.78%）和隐藻（6.76%）为主；浮游植物密度变化范围为13.9×104~105×104个/L，其中6月平均密度（54.92×104个/L）高于10月（27.22×104个/L），自然河流型水体平均密度低于其它两种类型水体。硅藻在自然河流型水体为绝对优势种，在过渡型水体和类湖泊型水体中其优势度降低，而蓝藻和绿藻优势度增加，但三种水体中以小环藻（Cyclotella sp.）平均优势度最大。各优势种6月生态位宽度Bi和生态位重叠ΔSOij分别为0.13~0.77和1.04~38.46，10月分别为0.10~0.80和3.55~39.48，和10月份相比，6月各优势种生态位宽度Bi较高，而优势种间生态位重叠ΔSOij数值较低，表明6月各优势种种间竞争态势相对均衡，群落状态相对稳定。Shannon-Wiener指数（H''）、Marglef指数（D）及Pielou均匀度指数（J）变化范围分别为1.99~2.69、2.56~5.88和0.50~0.78，总体表现为6月＞10月，自然河流型水体>过渡型水体>类湖泊型水体，各江段水体处于α-β中污染状态。浮游植物与环境因子的典范分析（Canonical Analysis）结果表明：透明度、流速、水温、溶解氧、总氮是影响浮游植物群落的主要环境因子，且不同优势种对环境因子的响应有所不同。研究可为金沙江下游梯级库区水资源保护和生态修复提供科学依据。     

大纵湖浮游植物群落特征及其与环境因子的关系

里下河腹地位于江淮两大水系交融地带,人类活动严重影响区域水生态环境。鉴于浮游植物群落结构及多样性可作为水环境变化重要指示生物,于2015-2017年对里下河腹地典型湖泊大纵湖浮游植物群落结构及环境因子进行逐月采样调查,分别采用藻类生物学指标和综合营养指数对大纵湖营养状态进行综合评价,并且基于相关性分析法,探讨浮游植物与水环境因子的响应关系。结果显示,大纵湖在调查期间共鉴定出浮游植物7门、123种,以绿藻、硅藻、蓝藻为主,分别为50、35、18种,占总种数的40.65%、28.46%、14.63%。全湖各采样点浮游植物的平均丰度为3.70×106 ~6.25×106 个/L;空间上略有差异,夏季藻类丰度较高,冬季最低。大纵湖各个采样点浮游植物优势种基本相同,共8种。浮游植物物种多样性指数和均匀度年均值分别为2.74和0.78,表明大纵湖处于轻-中度污染状态。综合营养指数显示,大纵湖处于轻度富营养状态,两者结果基本一致。相关性分析表明,水温（T）、透明度（SD）、浊度（TUB）和总氮（TN）是影响大纵湖浮游植物群落结构的主要水质指标。     

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.