圆斑星鲽sox9基因的克隆与表达

本研究筛选到圆斑星鲽(Verasper variegatus)的性别相关基因sox9，并通过RACE技术获得了全长序列，基因全长为3287 bp，包括1431 bp的ORF，编码477个氨基酸，368 bp的5¢ UTR和1488 bp的3¢ UTR。在3¢ UTR中有多聚腺苷酸尾和加尾信号AATAAA。通过荧光定量PCR测定了sox9基因在圆斑星鲽成鱼不同组织中的表达水平，发现sox9基因在圆斑星鲽的脑、眼、鳃、心、肝、胆、肠、精巢、卵巢、肾和肌肉等各个组织中都有不同程度的表达。在鳃、脑和精巢组织中检测到较高水平的sox9转录，其中精巢中的转录水平显著高于其他组织，sox9基因在性腺中的表达显示出性别两相性差异。其在精巢中的表达水平要显著高于卵巢，说明sox9基因与雄性性腺发育相关。通过测定sox9基因在圆斑星鲽幼鱼不同发育时期(20、30、40、50、60、70和80日龄)的表达水平，发现其在20~50日龄表达量逐渐下降，在60日龄时表达量上升，推测表达量上升可能与幼鱼性腺分化相关。     

圆斑星鲽MHCⅠα基因的克隆与组织表达分析

采用表达序列标签法和cDNA末端快速扩增(RACE)技术,成功获得了圆斑星鲽主要组织相容性复合体MHC Ⅰα的全长cDNA序列.该cDNA全长2171 bp,5'UTR为20 bp,3'UTR为1053bp,开放阅读框(ORF)长度为1098 bp,可编码365个氨基酸,包含信号肽、抗原结合域(α1、α2),IGC类似...     

圆斑星蝶MHC ⅡB基因结构、多态性及组织表达分析

通过表达序列标签法和cDNA末端快速扩增(RACE)技术,分离和克隆了圆斑星鲽(Verasper variegatus)主要组织相容性复合体(MHC)IIB的全长cDNA序列,该cDNA全长为1 144 bp,5'UTR(untranslated region)为7 bp,3'UTR为450 bp,开放阅读框(ORF)长度为687 bp,可编码228个氨基酸,包含信号肽、抗原结合域(β1),IGC区(β2),跨膜区和胞质区5个结构域.同源分析表明,圆斑星鲽MHC IIB氨基酸序列与其他硬骨鱼具有49%-79%的同源性,与鼠、人、红原鸡和护士鳖的相似性较低,分别为34%,33%,31%和30%.圆斑星鲽MHC IIB基因含有5个内含子,与其他硬骨鱼不同,其β2结构域编码区内存在I个109 bp的内含子.根据获得的MHC IIB基因组序列设计特异性引物,在10尾野生圆斑星鲽中扩增了包括完整内含子1和外显子2的长度约388 bp的DNA片段,PCR产物直接测序后发现在270 bp的抗原结合域中共有23个位点发生变异,密码子第1位和第2位的变异明显高于第3位.利用荧光定量PCR分析组织表达发现,MHC IIB基因在健康圆斑星鲽9种组织中均有表达,但表达量存在差异,肾的表达量最高,肌肉的表达量最低,肾、心、脾脏和鳃的表达量显著高于肝、皮肤、脑、血和肌肉.本研究旨在为MHC基因家族的遗传进化分析、结构与功能的解析提供基础,同时为圆斑星鲽的分子免疫学和标记辅助育种研究提供参考依据.     

圆斑星鲽MHC IIB基因结构、多态性及组织表达分析

通过表达序列标签法和cDNA末端快速扩增(RACE)技术,分离和克隆了圆斑星鲽(Verasper variegatus)主要组织相容性复合体(MHC)IIB的全长cDNA序列,该cDNA全长为1144bp,5'UTR(untranslated region)为7bp,3'UTR为450bp,开放阅读框(ORF)长度为687bp,可编码228个氨基酸,包含信号肽、抗原结合域(β1)、IGC区(β2)、跨膜区和胞质区5个结构域。同源分析表明,圆斑星鲽MHCIIB氨基酸序列与其他硬骨鱼具有49%～79%的同源性,与鼠、人、红原鸡和护士鲨的相似性较低,分别为34%、33%、31%和30%。圆斑星鲽MHC ⅡB基因含有5个内含子,与其他硬骨鱼不同,其β2结构域编码区内存在1个109bp的内含子。根据获得的MHC ⅡB基因组序列设计特异性引物,在10尾野生圆斑星鲽中扩增了包括完整内含子1和外显子2的长度约388bp的DNA片段,PCR产物直接测序后发现在270bp的抗原结合域中共有23个位点发生变异,密码子第1位和第2位的变异明显高于第3位。利用荧光定量PCR分析组织表达发现,MHCIIB基因在健康圆斑星鲽9种组织中均有...     

双棘黄姑鱼促性腺激素释放激素基因的克隆及系统进化分析

通过同源基因克隆方法得到双棘黄姑鱼促性腺激素释放激素(GnRH)的3个基因:cGnRH、sGnRH、sbGnRH,其开放阅读框为258、273bp和261bp,分别编码85个、90个和86个氨基酸,3个基因的信号肽为23个氨基酸,核心十肽分别是QHWSHGWYPG、QHWSYGWLPG和QHWSYGLSPG,这3种核心十肽经生物信息学分析均高度保守。氨基酸序列比对分析表明,双棘黄姑鱼与同科美国红鱼GnRHs基因亲缘性最近,它们的cGnRH和sGnRH的氨基酸同源性达100%,两种鱼sbGnRH的同源性也高达92.2%。用MEGA 4.0构建GnRHs Neighbour-joining系统进化树,结果显示双棘黄姑鱼cGnRH先于同科的美国红鱼聚类,再与星点东方鲀、斑马鱼和虹鳟等共同聚类;双棘黄姑鱼sGnRH则先后与其他鱼类sGnRH、cGnRH、sbGnRH聚类;而双棘黄姑鱼sbGnRH先后与其他鱼类的sbGnRH、cGnRH和sGnRH聚类。     

中华鲟热休克蛋白hsp30基因cDNA的克隆及其在高温胁迫下的表达分析

实验克隆了中华鲟(Acipenser sinensis)热休克蛋白hsp30基因cDNA的全长、分析了其分子结构与特征,并研究了其在高温胁迫下的表达水平。结果显示,中华鲟hsp30基因cDNA序列全长为1 037 bp,其中开放阅读框(ORF)636 bp,5′端非编码区(5′UTR)38 bp,3′端非编码区(3′UTR)363 bp,共编码211个氨基酸。氨基酸多序列比对发现含有一个保守的α晶状体结构;系统进化分析显示,中华鲟HSP30与鱼类HSP30聚为一支,与小体鲟HSP30氨基酸序列相似性最高,为79%。荧光定量PCR结果表明,中华鲟hsp30基因在皮肤中的表达量最高,肝脏次之,在肠中的表达量最低。高温胁迫后,心脏、脾脏、肾脏和皮肤中hsp30基因表达量均显著增加,表明这些器官在中华鲟应对高温胁迫中可能起着重要作用。     

圆斑星鲽piwil2基因的克隆与表达分析

本研究采用RACE末端扩增方法，得到全长为3872 bp的圆斑星鲽(Verasper variegatus) piwil2基因序列，命名为Vvpiwil2，开放阅读框(ORF)长为3192 bp，编码1063个氨基酸，5?-UTR和3?-UTR的长度分别140 bp和540 bp。基于ExPASy、SMART、Signal4.1和NCBI的保守结构域(CDD)数据库在线分析对蛋白序列结构进行预测，推断Vvpiwil2编码的氨基酸分子量为118.6 kDa，理论等电点为9.02，无跨膜结构及信号肽，有3个结构域：ArgoL1结构域、PAZ结构域及PIWI结构域。利用实时荧光定量PCR技术对圆斑星鲽不同发育时期的胚胎、仔稚鱼以及雌雄成鱼的不同组织表达模式进行分析。结果显示，Vvpiwil2基因从胚胎发育早期至高囊胚期均大量表达，之后呈下降趋势，直至孵化阶段。由于胚胎从卵裂至囊胚时期的发育过程主要受细胞质成分引导，直至原肠早期，mRNA开始大量转录合成，实现由母源型向合子型的过渡，推断Vvpiwil2是母源性基因。孵化后仔稚鱼68 d时，Vvpiwil2基因表达量显著高于其他时期，表明Vvpiwil2的功能可能与圆斑星鲽性腺分化过程相关；Vvpiwil2基因在雌雄成鱼性腺中的表达量显著高于其他组织，且卵巢中的表达量显著高于精巢，推测Vvpiwil2基因在卵巢功能的维持中发挥重要作用。本研究结果为解析圆斑星鲽性别决定机制提供了新的靶标基因，为建立全雌化苗种繁育技术打下坚实的理论基础。     

星突江鲽生长激素基因的克隆及体外重组表达分析

利用cDNA末端快速扩增技术(RACE)获得星突江鲽生长激素基因(GH)的cDNA序列全长为957 bp,其中开放阅读框(ORF)长615 bp,编码204个氨基酸,氨基酸序列与牙鲆同源性最高达到73.0%,系统进化显示,星突江鲽GH与其他鲽形目和鲈形目鱼类聚为一个分支。采用实时荧光定量PCR技术对GH基因的组织表达特性进行了分析,结果显示,GH基因mRNA主要在雌雄成鱼垂体中表达,同时在脑、性腺、肝脏、胃和肌肉中均检测到表达,雌鱼胃和肌肉中GH基因mRNA的表达量显著高于雄鱼(P0.05),表明星突江鲽GH可能主要通过旁分泌和自分泌方式参与性别二态性生长调节。本实验成功构建了体外重组表达质粒GH/pET28a,转化大肠杆菌BL21(DE3)经IPTG诱导可得N端含6个组氨酸的重组蛋白。重组蛋白主要以大小为24.9 ku的包涵体形式存在,Western-blotting免疫印迹呈阳性。包涵体经6 mol/L盐酸胍变性、Ni2+离子亲和柱纯化和尿素梯度复性后可得纯化GH蛋白;5.4和16.2μg/mL重组蛋白添加组中,人胚胎肾细胞HEK293T的增殖受到显著抑制。本研究结果可在分子和蛋白水平解析星突江鲽的生长调控机制。     

草鱼C1qC基因的克隆及表达分析

为了研究C1qC基因在草鱼(Ctenopharyngodon idella)免疫过程中所起的作用,利用RT-PCR和RACE方法克隆获得了C1qC基因cDNA全长序列,经序列分析表明,所克隆的C1qC cDNA全长为916 bp,包括开放阅读框(open reading frame,ORF)735 bp,5′端非编码区(untranslated region,UTR)89 bp和3′端非编码区(UTR)92 bp。735 bp的ORF共编码244个氨基酸,相对分子量为26 162.5 U。同源性分析表明,草鱼与斑马鱼(Danio rerio)的相似度最高,达到71%。经草鱼呼肠孤病毒(grass carp reovirus,GCRV)诱导后,草鱼C1qC基因在鳃、皮肤、肌肉、肝、中肾、心脏、头肾等组织中的mRNA表达水平均显著上调。在草鱼胚胎发育的各个阶段都能检测到C1qC mRNA的表达,说明该基因可能在草鱼胚胎和鱼苗的免疫反应和早期发育中起重要作用。本研究将为今后在草鱼免疫功能方面深入研究C1qC基因提供基础资料。     

草鱼ghrelin基因的分子克隆与组织分布及其摄食调控作用分析

ghrelin是一种在脊椎动物摄食调节过程中起重要作用的脑肠肽,具有明显的摄食促进作用。实验利用同源克隆技术获得了草鱼ghrelin基因的cDNA序列和DNA序列,其中cDNA序列全长506 bp,包括90 bp的5′端非编码区(5′-untranslated region,5′UTR),312 bp的开放阅读框(open reading frame,ORF),以及104 bp的3′端非编码区(3′-untranslated region,3′UTR)。开放阅读框编码的103个氨基酸的ghrelin前体肽,经剪切加工后形成含有19个氨基酸的成熟肽。氨基酸序列分析结果显示,草鱼ghrelin与硬骨鱼类ghrelin相似度最高,而与其他脊椎动物相似度较低,同时草鱼ghrelin成熟肽N端的"活性中心"(active core)为鲤科鱼类中常见的GTSF形式。与大多数硬骨鱼类的ghrelin基因结构相同,草鱼ghrelin基因也包括4个外显子和3个内含子。荧光定量PCR检测到ghrelin mRNA大量分布于草鱼的前肠和脾,脑、肾、肝、肌肉、皮和鳔等组织也有ghrelin mRNA分布。草鱼脑和肠中的ghrelin表达水平在摄食后下降,随着饥饿时间的延长表达水平逐步升高,最后维持在较高水平,表明ghrelin作为摄食启动信号对草鱼的摄食活动起到了促进作用。     

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.     

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.     

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.