中国对虾中肠盲囊的研究：I.中肠前盲囊的组织细胞结构和功能

中国对虾中肠前盲囊是由于肠最前端背壁伸出的突起盲囊，这一盲状突起与胃后腔背部及肝胰前端相连，意志支柱状上皮细胞层突入盲腔形成多分支讯管构构成中肠前盲囊；盲管上皮的柱状上皮细胞在形态上没有明显的区别，在柱状上皮细胞内有３种大小，电子密度不同的颗粒，用溶酶体标志酶作细胞化学染色显示；直径１μｍ左右，电子密度中等的颗粒是溶酶体颗粒，另外两种颗粒分别是粘蛋白颗粒和酶原颗粒，中肠前盲囊上皮细胞吸收的物质主要     

缢蛏消化盲囊的组织学与组织化学

运用光镜、透射电镜及组织化学方法研究了缢蛏消化盲囊的结构与功能。消化盲囊为复管泡状腺，以导管与胃腔相通。腺上皮由胚性细胞(E-细胞)、纤维细胞(F-细胞)、吸收细胞(R-细胞)和分泌细胞(B-细胞)组成，它们在分布位置、结构及功能等方面各有其特点：E-细胞主要存在于近端(与导管相连处)，体积较小、核质比大，能分化为其它类型的腺细胞；F-细胞内含发达的粗面内质网和游离核糖体，功能是合成、分泌消化酶；R-细胞以脂肪滴和糖原粒的形式储存丰富的能量；B-细胞只见于远端，游离端具发达的微绒毛，内含大量的次级溶酶体和消化残体，有很强的吸收和细胞内消化功能；B-细胞和R-细胞消化脂类的能力较强。导管壁由单层短柱状纤毛细胞和丰富的粘液细胞构成，纤毛柱状细胞能合成、分泌消化酶。消化盲囊参与无机盐代谢。     

中国对虾幼体中肠腺的结构和细胞化学研究

用组织学、细胞学以及细胞化学等手段对中国对虾中肠腺的结构发生和功能进行研究。结果表明，中肠腺始于Ｎ４－５期，为中肠前端先后向两侧突出的２对盲囊，第１对中肠腺盲惠至Ｍ３期退化消失，成体中肠腺由第２对中肠腺盲囊发育而成。中肠腺小管上 Ｚ２期细胞已有了分化，由４类细胞组成，即胚细胞（Ｅ细胞）、纤维细胞（Ｆ细胞）、泡状细胞（Ｂ细胞）和吸收细胞（Ｒ细胞）。电镜下，腺上皮细胞在发育的各个时期基本一致；Ｅ细胞的     

真鲷幼鱼消化道组织学研究↑（*）

６月龄真鲷（Ｐａｇｒｏｓｏｍｕｓｍａｊｏｒ）幼鱼通过解剖,切片、染色和显微摄像,结果表明：整个消化道从解剖水平可以分为口、口咽腔、食道、胃、肠及直肠等６个功能区。口部有犬齿、臼齿和不规则的粒状齿;口腔内有咽（含咽齿）及鳃耙,鳃耙形成了对食物颗粒的屏障,面向食管保护鳃丝;短的食管起源于咽腔,终止于胃,两者间没有明显的解剖上的差别;Ｙ型的胃分为贲门部、幽门部和胃盲囊３部分。组织学观察可见：胃由单层柱状上皮细胞组成,在贲门区和幽门区的上皮层下面,具有相似细胞组成的胃腺;有４个幽门盲囊,幽门盲囊与肠组织结构基本一致。胰腺管和肝管从幽门盲囊的基部生出。肠道短,肠道前部起源于幽门括约肌之后,在肠瓣处变窄,使整个肠道分为肠和直肠两部分;肠与直肠相比粘膜上有较多的褶皱;肠道上皮由柱状上皮细胞和粘液分泌细胞组成,粘膜下层有致密的结缔组织和大量嗜酸性颗粒的细胞。     

虾蛄消化系统的组织学和组织化学研究

虾蛄（ Ｓｑｕｉｌｌａ ｏｒａｔｏｒｉａ） 的消化系统由消化道和中肠腺组成,前者包括口、食道、贲门胃、幽门胃、中肠和中肠盲囊、后肠以及肛门。中肠腺甚为发达,为复管状腺,腺管上皮由分泌细胞、储存细胞、吸收细胞和胚细胞４ 种类型细胞组成。分泌细胞的顶端有一明显的分泌囊泡,呈现蛋白酶、非特异性酯酶和脂酶活性,可通过分泌囊泡外排或顶端细胞质崩解而向腺腔分泌水解酶类,后者进入消化道对食物进行细胞外消化。吸收细胞细胞质内含丰富的ＲＮＡ 和蛋白质,表明该细胞具有旺盛的蛋白质合成功能。储存细胞含有糖原和脂类,其基部质膜显示碱性磷酶酶活性,表明储存细胞可将细胞内的营养物质转运至腺管间的血窦。胚细胞体积较小,胞质嗜碱性,但细胞核大而圆。消化道粘膜上皮主要为柱状细胞,贲门胃和幽门胃上皮细胞表面有几丁质层覆盖。贲门胃肌层发达,主要起机械研磨食物的作用。幽门胃的几丁质层特化形成间壶腹脊和壶腹上脊,两者相互配合而起过滤作用。中肠粘膜上皮细胞表面无几丁质层,上皮细胞呈现蛋白酶、非特异性酯酶和脂酶活性,表明中肠也能分泌消化水解酶。中肠上皮细胞具有微绒毛,亦表明中肠可能参与食物的吸收。后肠肠腔虽宽大,但其上皮细胞仅呈现较弱的非特异性酯酶活性,故后     

栉江Zhao消化系统组织学与组织化学的研究

运用组织学和组织化学方法对栉江Zhao系统的结构和功能进行了研究。栉江Zhao消化管的粘膜上皮由纤毛柱状细胞和杯状细胞组成，唇瓣、中肠和上行肠的上皮层还有嗜酸性粒分泌细胞，消化盲囊的腺上皮由分泌细胞和消化（吸收）细胞组成。皮下结缔组织中富含血腔隙、结缔组织和血腔隙中有“颗粒细胞”。食道、胃、中肠、晶杆囊及消化盲囊能分泌消化酶，对食物进行消化和吸收；结缔组织，“颗粒细胞”也参与了食物的消化吸收。唇瓣、食道、晶杆囊和中肠的上皮细胞及结组织中的“颗粒细胞”内含铁、结缔组织中含钙。     

口虾蛄幽门胃、中肠、后肠及中肠腺形态组织学观察

为研究渤海湾口虾蛄(Oratosquilla oratoria)幽门胃、中肠、后肠及中肠腺的形态学及组织学结构,采用解剖及石蜡切片显微技术观察了口虾蛄消化道形态结构及幽门胃、中肠、后肠及中肠腺的组织构成。口虾蛄消化道由口、食道、贲门胃、幽门胃、中肠、后肠和肛门组成;幽门胃腔分为背室和腹室,背室黏膜上皮细胞呈高柱状,表面覆盖有薄的几丁质层,腹侧上皮细胞呈低柱状,和黏膜下层向胃腔突起形成皱襞,腹侧表面的几丁质层特化为间壶腹嵴;中肠壁自内向外分别为上皮组织、结缔组织和肌肉组织,内壁纵行褶皱明显,外壁被中肠腺包裹;中肠腺上皮细胞有分泌细胞、储存细胞、吸收细胞和胚胎细胞;后肠结构简单,后肠腔大于中肠腔。口虾蛄消化道的结构特征及幽门胃、中肠、后肠结构特点与其肉食性相适应。     

栉江珧消化系统组织学与组织化学的研究

运用组织学和组织化学方法对栉江珧消化系统的结构和功能进行了研究.栉江珧消化管的粘膜上皮由纤毛柱状细胞和杯状细胞组成,唇瓣、中肠和上行肠的上皮层还有嗜酸性粒分泌细胞;消化盲囊的腺上皮由分泌细胞和消化(吸收)细胞组成.皮下结缔组织中富含血腔隙,结缔组织和血腔隙中有"颗粒细胞".食道、胃、中肠、晶杆囊及消化盲囊能分泌消化酶,对食物进行消化和吸收;结缔组织、"颗粒细胞"也参与了食物的消化吸收.唇瓣、食道、晶杆囊和中肠的上皮细胞及结缔组织中的"颗粒细胞"内含铁,结缔组织中含钙.     

褐菖鲉消化道的组织学和组织化学

褐菖鲉消化道的组织学和组织化学=Study on histology and histochemistry of digestive tract in Sebastiscus marmoratus[刊，中]/石戈（浙江海洋学院海洋科学学院，浙江 舟山 316004），王健鑫，刘雪珠，王日昕//水产学报.－2007，31（03）.－293～302 利用光镜技术对褐菖鲉消化道进行了组织学和组织化学研究。组织学研究表明：褐菖鲉消化道由口咽腔、食道、胃和肠4部分组成。口咽腔较大，上下颌，犁骨及腭骨均有细齿带,粘膜由复层鳞状上皮组成，并含有大量黏液细胞和少量杯状细胞；食道粗而短，上皮组织包括扁平上皮层区域和单层柱状上皮层区域，上皮含有大量杯状细胞和黏液分泌细胞，粘膜层的固有膜中含有腺体；胃呈Y型，包括贲门、胃体和幽门3个区域，胃粘膜由单层柱状上皮组成，在贲门和胃体部的粘膜层中有厚的结实层，上皮有大量的胃小凹和胃腺组织；胃幽门部括约肌明显，幽门上皮不含胃小凹；胃与肠相接处有8～9个指状幽门盲囊，其形态学和组织学特征与前肠类似；肠道上皮由单层柱状上皮细胞组成，丰富的微绒毛形成明显的纹状缘，上皮中含有大量杯状细胞，肠道系数为0.54。组织化学研究显示：幽门、幽门盲囊和肠上皮细胞顶端胞质和纹状缘具碱性磷酸酶活性；幽门盲囊及肠道上皮细胞顶端胞质中检测到酸性磷酸酶活性；在贲门部和胃体部的固有层以及幽门上皮还检测到酯酶活性，且酯酶定位于幽门柱状上皮细胞胞质的上半部。整个消化道的粘膜层中存在许多粘液细胞：食道上皮含大量酸性粘液细胞，胃上皮细胞均含有中性粘液，而肠道由前向后中性粘液物质逐渐减少，酸性粘液物质逐渐增多。组织学和组织化学的结果表明褐菖鲉食道有润滑和微弱的消化作用，胃有消化脂类和吸收糖类的功能；幽门和盲囊有较强的吸收脂类的功能；前肠、中肠和后肠有活跃的细胞内消化和吸收功能，整个消化道结构与其肉食性功能密切相关。图3参29     

单环刺螠虫消化道组织学和细胞学

对单环刺螠虫(Urechis unicoinctus VonDrasche)消化道的结构进行了组织学和细胞学观察。单环刺螠虫消化道可分为咽、食道、嗉囊、砂囊、胃、中肠、呼吸肠、直肠和排泄腔。咽、食道和直肠管壁由内向外分为粘膜层、粘膜下层、肌层和外膜，嗉囊、砂囊、胃、中肠和呼吸肠壁仅由粘膜层和外膜组成。除食道外，胃之前的消化道及直肠上皮细胞均有发达的纤毛，中肠和呼吸肠上皮主要为微绒毛。消化道上皮主要分为3类细胞，第1种为柱状上皮细胞；第2种为粘液细胞；第3种为分泌细胞。粘液细胞和分泌细胞散布于柱状上皮细胞之间，且结构和数量随部位而异：粘液细胞在咽、食道、嗦囊、胃、中肠和直肠上皮中有较多的分布，分泌细胞在砂囊、胃、中肠和呼吸肠中数量较多。     

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.