鳙肌原纤维三聚磷酸盐水解酶(TPPase)的活性

采用离子色谱方法检测添加的三聚磷酸盐（STPP）在新鲜碎鳙肉和鳙肌原纤维蛋白中Mf）所发生的水解。研究结果表明，添加到新鲜碎鳙肉中的STPP能被水解成焦磷酸盐（PP）和单磷酸盐（Pi），所生成的PP继续水解，最终产物为Pi。鳙肌原纤维蛋白具有三聚磷酸盐水解酶（TPPase）活性，能将STPP水解成PP和Pi。鳙肌原纤维蛋白TPPase水解STPP的最适温度为25 ℃，最适pH为5.5。低浓度的Mg²⁺能够激活鳙肌原纤维蛋白TPPase ，但Mg²⁺超过5 mmol·L^-1时却起到了抑制作用。鳙肌原纤维蛋白TPPase活性受到KCl的影响，在0.3 mol·L^-1 KCl 条件下活性最高。EDTA-Na₂能够抑制鳙肌原纤维蛋白TPPase活性。     

磷浓度对２种有毒亚历山大藻生长和产毒力的影响

采用显微镜细胞计数和标准藻毒监测方法—小鼠生物法,研究了4种磷浓度0µmol•L-1、1.8µmol•L-1、3.6µmol•L-1和5.4µmol•L-1对有毒甲藻塔玛亚历山大藻(Alexandrium tamarense)和微小亚历山大藻(Alexandtium minutum)的生长和产毒力的影响。结果表明,磷浓度对两种甲藻的生长和产毒能力都有显著性影响(p<0.05)。3.6µmol•L-1磷浓度组的塔玛亚历山大藻密度显著高于其它3个磷浓度组,0µmol•L-1磷浓度组显著低于其它3个磷浓度组。微小亚力山大藻在1.8µmol•L-1、3.6µmol•L-1和5.4µmol•L-1磷浓度下生长没显著性差异(p>0.05)。但在0µmol•L-1磷浓度下生长缓慢,藻密度显著低于其它3个有磷组。0µmol•L-1磷浓度下塔玛亚历山大藻和微小亚历山大藻的产毒能力最高, 显著高于其它磷浓度组(p<0.05),分别为3 MU•10000cells-1和5.2MU•10000cells-1。其它磷浓度组两种有毒甲藻的产毒能力没有显著性差异(p>0.05)。     

邻苯二甲酸丁基苄酯（BBP）对斑马鱼的毒性效应研究

经急性毒性试验，求得邻苯二甲酸丁基苄酯（BBP）对斑马鱼96小时半致死浓度（LC50）为3.98 mg•L-1。在此基础上，设置4个浓度梯度：0、0.332、0.665、1.33 mg•L-1，研究了在不同的时间（7、14、21、28d）暴露下，BBP对斑马鱼超氧化物歧化酶（SOD）、乙酰胆碱酯酶（AChE）、过氧化氢酶（CAT）活性的影响。结果表明，随着时间的延长，SOD活性呈现先上升后下降的趋势，在14d时，各处理组SOD活性达到最高水平；实验期间（0-28d），各处理组AChE活性被显著抑制，整体呈现下降趋势；CAT活性，在7d时，除0.665 mg•L-1浓度组有极显著抑制作用（p＜0.01）外，其余各浓度组CAT活性均与对照接近，无显著差异，14d开始，除了0.332 mg•L-1浓度组高于对照组，其他浓度组与对照组相比均呈现先下降后上升的趋势。BBP对斑马鱼SOD、AChE、CAT活性产生的影响，其变化可作为水体污染的分子生物标记物，为制订BBP水质标准及对其进行生态风险评价提供科学依据。     

斑点叉尾鮰源嗜麦芽寡养单胞菌胞外蛋白酶的纯化及性质研究

采用硫酸铵盐析，DEAE Sephadex A－50凝胶层析等方法从嗜麦芽寡养单胞菌胞外产物中提纯了一种分子量为45.7 ku的单一多肽蛋白酶。该酶对小鼠和斑点叉尾鮰具有明显的致死作用，其LD50分别为4.33 μg•g-1体重和3.49 μg•g-1体重。酶的最适温度为20 ℃，热稳定性差，100 ℃作用15 min酶活完全丧失，最适pH为9.0，PMSF对酶活无影响，部分金属离子如Ca2+、Hg2+、Cu2+能使酶活性明显下降，而Co2+对酶有一定程度的激活作用，EDTA能完全抑制酶活性，表明该酶为一种金属蛋白酶。图1表4参29     

绒线藻凝集素的分离纯化及生物活性

将海洋红藻－绒线藻（Dasya villosa）经磷酸盐缓冲液抽提，20%～75%硫酸铵分级沉淀， Sephadex G－200分子筛层析，得到绒线藻凝集素（DVL）。用Sephadex G－200分子筛层析测得其分子量为547 ku。该凝集素凝集兔红细胞的作用不被D-果糖、D-半乳糖、葡萄糖、蔗糖、甘露聚糖、γ-球蛋白所抑制，仅被牛甲状腺球蛋白所抑制，最小抑制浓度为96.88 mg•L-1。2价金属离子Ca2+、Mg2+及EDTA对该凝集素凝集活性没有影响。其凝集活性在25～80 ℃保持不变为28，90～100 ℃加热30 min，活力为27，仍保留50%的活性,说明其具有较强的耐热性。经t检验，注射腹水型肝癌H22肿瘤细胞小鼠在DVL为低（65 mg• kg-1）、中（130 mg•kg-1）高（260 mg•kg-1）剂量时：肝指数、脾指数与生理盐水对照组的均无显著差异；抑瘤率分别为21%、27%、40%，DVL的低、中剂量下抑瘤率与生理盐水对照组的均无显著差异；在高剂量下DVL具有显著的抑制肿瘤细胞生长的作用（P<0.05）。图2表5参21     

草鱼酸性磷酸酯酶的性质及金属离子对其活性的影响

以草鱼肝脏为材料提取一种酸性磷酸酯酶(ACPase,EC.3.1.3.2),进一步用(NH4)2SO4沉淀分离,Sephadex G-200柱纯化,经聚丙烯酰胺凝胶电泳纯度鉴定呈现单一酶蛋白带,该酶紫外吸收峰为240nm和280nm,等电点为4.8,相对分子质量为100046.1。该酶水解对硝基苯磷酸二钠(pNPP)的最适pH值为4.4,最适温度为45℃,并有热激活现象,热激活温度为60℃。耐热实验表明,该酶在最适温度下耐热时间为33min,最适温度下20min时表现出最大活性。在60℃下耐热时间为25min,15min时表现最大活性。酶促反应初速度为0.0475μmol/min,最大反应速度为0.153μmol/min。米氏常数Km值为3.56×10-3mol/L。金属离子对酶活性影响的研究结果表明,K+对酶有激活作用,Li+、Na+对酶的活性没有明显影响;碱土金属离子Mg2+、Ca2+和Ba2+对酶有激活作用,其激活程度由大到小依次为:Ba2+、Mg2+、Ca2+;Mn2+对酶有激活作用,Zn2+、Cu2+、Co2+则有抑制作用;重金属离子Hg2+、Pb2+、Ag+和Cd2+对酶有抑制作用,其中Hg2+的抑制效应最强。Mg2+和Cu2+的作用机制研究结果表明,Mg2+对酶具有混合型激活作用,Cu2+对酶具有竞争性抑制作用。     

贻贝蛋白酶解降血压肽的降压活性及相对分子质量与氨基酸组成

以贻贝（Mytilus coruscus）为原料制取降血压肽，采用均匀设计试验探讨了不同酶解条件对其ACE( angiotensin converting enzyme) 抑制活性的影响，利用高效液相色谱分析了其相对分子质量分布，以氨基酸自动分析仪分析其氨基酸和游离氨基酸组成；并利用自发性高血压大鼠（SHR)饲喂试验检测其降血压活性。结果表明，对于P1酶来说, 酶量从25~175 IU• mL-1，酶解时间从2~7 h，随着酶解程度的提高，其ACE抑制率下降；其最高的ACE抑制率为88.08%，对应的最佳酶解条件为：酶量25 IU•mL-1，酶解时间2 h，pH 7.0，酶解温度60 ℃。此外发现降血压肽的相对分子质量在1.6 ku以下，其中10肽以下的短肽约占50.4%，证实了降血压肽主要以分子量较小的短肽组成。降血压肽游离氨基含量为8.8 g•（100g）-1，水解氨基酸总量为59.6 g•（100g）-1，疏水性氨基酸含量为24.86 g•（100g）-1，氨基酸组成比例平衡，必需氨基酸含量丰富,其中含量最高的氨基酸是谷氨酸,占8.57%。此外以3.0 g•kg-1体重的降血压肽样品剂量饲喂SHR，在饲喂后2～6 h降压效果显著，平均降低幅度为18～28 mmHg（P＝0.05）。研究表明以贻贝等水产蛋白为原料可开发具有高ACE抑制活性和显著降血压作用的降血压肽。     

淡水环境下3种红树植物对氮磷的去除效应应

2010年7 ~ 12月,通过水培盆栽试验研究了桐花（Aegiceras corniculatum）、海莲（Bruguiera sexangula）和无瓣海桑（Sonneratia caseolaris）对生活污水的净化效果,设置了3个浓度梯度,即N1P1（TN 为3.96 mg• L-1,TP为 0.47 mg• L-1）,N2P2（TN为 19.8 mg•L-1,TP 为2.35 mg•L-1）和N3P3（TN为 39.6 mg•L-1,TP为 4.7 mg•L-1）。研究结果表明：随着水培时间的增加,水体盐度、总氮和总磷含量显著下降（P <0.001）。桐花、海莲和无瓣海桑对生活污水总氮去除率达74.5% ~ 97.4%,总磷去除率达72.3% ~ 95.7%。栽培有红树植物的系统对氮磷的去除率显著高于无植物系统,分别为无植物的1.28倍 ~ 3.2倍和1.24倍 ~ 2.71倍。红树植物氮磷质量分数分别为6.81 mg•g-1±0.85 mg•g-1 和 1.41 mg•g-1±0.46 mg•g-1。当污水浓度低时（N1P1）,红树植物主要是通过累积作用去除水体氮磷,占总去除效应的42.2% ~ 63.3%和46.1% ~ 85.8%。当污水浓度高时（N3P3）,红树植物氮磷累积量仅占4.5% ~ 10.4%和6.7% ~ 14.9%。     

扁吻鱼保护生物学研究---栖息地饵料、鱼类群落

2003年以来作者对现今扁吻鱼唯一栖息地生物饵料及鱼类群落环境进行了初步研究。结果显示：克孜尔水库有浮游植物7门34种（属），平均密度145.7×104ind•L-1，平均生物量1.225mg•L-1，硅藻密度及生物量均占优势；浮游动物35种（属），平均密度958.6ind•L-1，原生动物占优势；平均生物量1.449mg•L-1，枝角类和桡足类占优势；底栖动物1种（属），平均密度9.1ind•m-2，平均生物量0.08g•m-2；水生植物2种（属）。栖息地分布鱼类19种，土著种10种，外来种9种，隶属2目3科13属，其中鲤科15种，占78.9%，鳅科3种，占15.8%，鱼叚虎鱼科1种，占5.3%。初步探讨了扁吻鱼所面临的生态环境问题。     

尼罗罗非鱼淀粉酶性质的初步研究

研究了尼罗罗非鱼(Oreochromis niloticus)肝脏淀粉酶的基本性质及金属离子对该鱼淀粉酶活性的影响。结果表明:罗非鱼淀粉酶活力的最适pH是6.5,最适底物浓度是2%。研究金属离子对该鱼淀粉酶活力影响,一价金属离子K+、Li+、Na+对酶活力影响较小;二价金属离子Cu2+对酶活力具有抑制作用,Zn2+对酶活力无明显影响;三价金属离子Al3+对酶活力具有抑制作用,但效果不是很强烈,Fe3+对酶活力具有明显的激活作用;碱土金属Mg2+、Ca2+对淀粉酶活性有激活作用,而Ba2+对酶具有抑制作用;重金属离子Cd2+、Pb2+有明显的抑制作用。     

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.     

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.