14种微藻总脂含量和脂肪酸组成研究

比较分析了14种微藻的总脂含量和脂肪酸组成,结果表明：除小球藻、亚心形扁藻、极微小环藻、微绿球藻外,其他微藻的总脂含量均超过其干重的10％。每一纲的微藻脂肪酸组成都有各自特点,绿藻纲中16：0、16：1(n-7)、18：1(n-9)含量较高,但微绿球藻中16：1(n-7)、20：5(n-3)(EPA)含量远高于其他绿藻;金藻纲中含大量14：0、16：0、18：3(n-3)、22：6(n-3)(DHA);硅藻纲中14：0、16：0、16：1(n-7)、EPA含量较高;黄藻纲的异胶藻富含16：0、16：1(n-7)和EPA。     

海、淡水驯化对5种微藻脂肪酸组成的影响

对5种微藻进行了脂肪酸分析及海淡水驯化影响其脂肪酸组成的研究,结果表明：谈水小球藻和海水小球藻的特征脂肪酸均为16：0、16：2、18：0、18：2和18：3;淡水斜生栅藻的特征脂肪酸为16：0、18：1和18：3;海水三角褐指藻的特征脂肪酸为14：0、16：0、16：1和EPA。淡水藻海水驯化和海水藻淡水驯化后,特征脂肪酸的种类不发生变化,但各种脂肪酸的含量有明显变化,驯化后,几种特征脂肪酸及总脂肪酸占细胞干重的比例在蛋白核小球藻、小球藻－1和三角褐指藻SS02品系中均有不同程度的提高,而在斜生栅藻、小球藻－2和三角褐指藻ZS08、XSO3品系中均有不同程度的下降。     

三角褐指藻甘油酯对氮胁迫的响应

【背景】三角褐指藻作为生物燃料潜在的生产者,在胁迫条件下能通过改变其甘油酯组成来适应外部环境的变化,同时伴随着生物燃料原料甘油三酯(TAG)的积累,研究三角褐指藻甘油酯对氮胁迫的响应机制有利于深入认识TAG的积累过程。【目的】通过分析三角褐指藻在正常和氮胁迫条件下各类脂质含量及其脂肪酸成分的变化,揭示氮胁迫诱导积累的TAG酰基主要来源,以及在胁迫前生成的各极性甘油酯脂肪酸的去向,从而为进一步认识三角褐指藻对氮胁迫的响应机制提供新信息。【方法】利用高效薄层色谱结合气相色谱法分析三角褐指藻在正常和氮胁迫条件下的脂肪酸及甘油酯组分的变化。【结果】三角褐指藻在氮胁迫条件下TAG含量增加至57.8 mg/g时,总甘油酯含量几乎不变,但各甘油酯含量变化差异很大,表现为各极性脂含量显著降低。在此期间,各类甘油酯脂肪酸组成含量的变化表明,三角褐指藻TAG主要积累饱和及单不饱和脂肪酸,即16:0和16:1n7,分别以从头合成及原有极性脂转化为主,极性脂的部分二十碳五烯酸(EPA)作为酰基供体也向TAG发生了转化;此外组成极性脂的多不饱和脂肪酸16:2n4、16:3n4及EPA分解导致其含量显著下降。【结论】当氮胁迫诱导的三角褐指藻TAG含量为57.8 mg/g时,积累的TAG酰基中有48%来自从头合成,52%来自极性脂转化;而氮胁迫诱导所减少的极性脂酰基中有54%转化成TAG,46%发生了分解。     

分离自象山港的15种海洋微藻脂肪酸比较研究

在160μmol.m-2.s-1光强、（20±2）℃条件下对分离自象山港的15种海洋微藻进行培养,在稳定期离心收集,冷冻干燥后用Bligh-Dyer法提取总脂,皂化衍生化后用气相色谱-质谱联用分析系统对其含有的脂肪酸进行定量和定性的分析。结果表明,这15种微藻总脂含量均较高,其中有9种微藻的总脂含量超过干重的10%,中心硅藻纲中共有的含量相对较高的主要脂肪酸为C14∶0、C16∶0、C16∶1（n-7）脂肪酸和EPA,针胞藻纲的赤潮异湾藻则含有高比例的C16∶0、C18∶4（n-3）和EPA,纵裂甲藻纲和甲藻纲中共有的含量相对较高的主要脂肪酸为C16∶0、C18∶4（n-3）、C18∶5（n-3）和DHA,而隶属于定鞭藻门颗石藻纲的颗石藻含量相对较高的主要脂肪酸分别为C16∶0、C18∶4（n-3）和DHA。这些藻是否可以作为生物饵料还需实际养殖投喂效果决定。     

10种海洋微藻总脂、中性脂和极性脂的脂肪酸组成

研究了10种海洋微藻的总脂、中性脂和极性脂的脂肪酸组成特征。海洋微藻的脂肪含量均在15％以上。极性脂一般为海洋微藻的主要脂类,是长链多元不饱和脂肪酸的主要提供者。中性脂含短链脂肪酸较多,为主要的储存脂类。绿藻纲可以将高含量的16:4(n-3)和18:3(n-3)作为化学分类的标记脂肪酸,小球藻和微绿球藻有丰富的20:5(n-3),与绿藻纲显著不同,可能属于大眼藻纲。绿枝藻纲的脂肪酸组成与绿藻纲类似,绿胞藻纲以16:0、18:4(n-3)和20:5(n-3)为主要脂肪酸。脂肪酸组成可用于海洋微藻的分类学研究,并能指导利用海洋微藻生产高度不饱和脂肪酸。     

九种海洋微藻总脂含量及脂肪酸组成分析

从广东沿海分离出9 种海洋微藻(包括6 种绿藻, 2 种金藻, 1 种硅藻), 在低氮并持续通入二氧化碳(1% CO2)条件下测试其总脂含量, 对其中总脂含量超过其干重45%的海洋微藻进行脂肪酸组成分析并优化反应条件。结果表明,9 种海洋微藻的总脂含量存在着明显差异, 介于8.9%-55.77%之间。其中, 海洋小球藻Chlorella sp.、眼点拟微绿球藻Nannochloropsis oculata、绿色巴夫藻Pavlova viridis 和微拟球藻Nannochloropsis sp.的总脂含量超过干重的45%, 而且, 这4 种富油海洋微藻的C16 和C18 脂肪酸含量丰富, C16:0、C16:1(n-7)、C18:1(n-9)含量较高, C14-C18 长链脂肪酸的含量超过总脂肪酸含量的80%。4 种高脂微藻在30 ℃高温培养条件下比生长速率均超过1.0 d−1。研究结果可为高温富油海洋微藻的工业化培养提供参考依据。     

有机碳源对三角褐指藻生长、胞内物质和脂肪酸组分的影响

研究了3种有机碳对三角褐指藻生长、胞内物质和脂肪酸组分的影响。结果表明, 三角褐指藻具有利用有机碳进行兼养生长的能力, 生长速率加快, 倍增时间缩短, 生物量显著提高, 100 mmol/L甘油兼养的生物量最高(713 mg/L), 是自养(460 mg/L)的1.60倍, 乙酸钠和葡萄糖兼养的生物量分别是自养的1.28倍和1.21倍。兼养下蛋白质含量较自养明显下降, 碳水化合物和总脂含量高于自养, 乙酸钠和甘油兼养的总脂含量分别是自养的1.43倍和1.20倍, 葡萄糖兼养的总脂含量与自养无明显差异。3种有机碳兼养的饱和脂肪酸和单不饱和脂肪酸占总脂肪酸的比例增大, 多不饱和脂肪酸比例降低, EPA(eicosapentaenoic acid)比例降低, 乙酸钠兼养的胞内EPA含量(6.23%)和产量(36.59 mg/L)均高于自养, 分别是自养的1.10倍和1.40倍, 甘油和葡萄糖兼养的EPA含量和产量均低于自养。     

5种藻和2种酵母对萼花臂尾轮虫饵料效果的比较研究

采用蛋白质和脂肪酸两项指标评价了7种饵料,包括5种藻(蛋白核小球藻、斜生栅藻、小球衣藻、卵形隐藻、中型裸藻)和2种酵母(面包酵母和啤酒酵母)对萼花臂尾轮虫的营养价值。蛋白质的评价结果显示,轮虫体总氮(TN)的含量为10．08％;粗蛋白(CP)的含量为63．0％;总氨基酸(TAA)占粗蛋白的48．10％;总必需氨基酸(TEAA)占粗蛋白的22．02％;TEAA与TAA的比值(TEAA／TAA)为45．8。在7种饵料中TN的含量在6．57％—10．96％之间,其中在卵形隐藻中的含量最高,在面包酵母中的含量最低;粗蛋白的含量介于41．06％—68．54％之间,在各饵料中含量由高到低的排列顺序与TN一致;TAA的含量在54．694—73．235之间,其中在斜生栅藻中的含量最高,在卵形隐藻中含量最低;TEAA的含量在23．836—34．136之间,其中在面包酵母中含量最高,在卵形隐藻中含量最低：TEAA／TAA比值在43．3—49．1之间,其中两种酵母的该比值最大。实验共测出17种氨基酸。轮虫蛋白质中以组氨酸含量最低(0．540％),其次为蛋氨酸(0．556％)和胱氨酸(0．762％);含量最高的是天门冬氨酸(5．206％)和甘氨酸(4．571％)。其饵料蛋白质中含量较低的是蛋氨酸(0．421％—1．495％)、组氨酸(0．675％—1．967％)和胱氨酸(0．439％—3．332％);含量较高的是谷氨酸(6．073％—11．447％)、天门冬氨酸(5．519％—8．281％)和亮氨酸(4．143％—7．473％)。分别用全卵蛋白和轮虫蛋白作为标准测得各种饵料的第一限制氨基酸有所不同,前有6种是蛋氨酸,1种为组氨酸(蛋白核小球藻);后有5种为异亮氨酸,另2种分别为蛋氨酸(蛋白核小球藻)和赖氨酸(啤酒酵母)。本项综合结果显示,蛋白核小球藻、斜生栅藻和两种酵母的蛋白质营养价值较高。脂肪酸的评价结果显示,饵料中粗脂肪的含量在1．64％—15．41％之间,其中中型裸藻中含量最高,啤酒酵母中含量最低。在7种饵料中共测出29种脂肪酸,其中中型裸藻和卵形隐藻中含量最为丰富,分别检出24种和22种;而在面包酵母和啤酒酵母中较缺乏,只检出9种和13种。5种饵料中不饱和脂肪酸的含量高于饱和脂肪酸的含量,其余2种饵料(斜生栅藻和啤酒酵母)则相反;5种藻中不饱和脂肪酸含量最高的是18：3ω3,其值在11．76％—26．58％;卵形隐藻的18：4ω3和小球衣藻的16：4ω3的含量亦较高,分别为22．59％和15．48％;在卵形隐藻和中型裸藻中,长碳链(二十碳以上的)不饱和脂肪酸的含量丰富,其含量为：中型裸藻16．2％,卵形隐藻18．7％,而在其他饵料中则较缺乏。除啤酒酵母外,饵料中缺乏的高度不饱和脂肪酸,均可在其培养的轮虫中检出,说明该轮虫可能具有将18：4ω3和18：3ω3转化为20：5ω3和22：6ω3等ω3系列高度不饱和脂肪酸(ω3HUFA)的代谢机制。用藻培养的轮虫,富含鲤科鱼类所必需的脂肪酸(18：2ω6和18：3ω3),其中蛋白核小球藻轮虫的含量最高(17．36％和24．64％),其次为斜生栅藻轮虫(12．23％和21．66％);面包酵母轮虫的ω3HUFA的含量占第四位,即脂肪酸营养价值较高。由此项指标得出结论,蛋白核小球藻和斜生栅藻是该轮虫工厂化培养的首选饵料,面包酵母是很有前途的饵料。这与7种饵料的投喂效果实验和蛋白质营养价值的评价结果基本一致。     

水杨酸对两种海洋微藻生长及油脂积累的影响

水杨酸(salicylic acid,SA)作为一种植物细胞的内源信号分子,在植物信号传导及抗逆反应中发挥着重要作用。研究不同浓度水杨酸对拟微绿球藻和三角褐指藻的生长、光化学活性及油脂积累的影响。结果表明:低于4μg/mL的水杨酸处理能促进拟微绿球藻的生长,而高于12μg/mL的水杨酸处理会抑制拟微绿球藻生长;水杨酸的处理对三角褐指藻的生长具有抑制作用,并且在2. 5~40μg/mL范围内,水杨酸质量浓度越大,抑制生长的作用越强。水杨酸处理会使拟微绿球藻的光系统Ⅱ(PSⅡ)实际光合效率(YⅡ)显著增加,但水杨酸处理会降低三角褐指藻的YⅡ。此外,8~12μg/mL的水杨酸处理能够促进拟微绿球藻的油脂积累,使其分别增加了23. 21%及45. 87%,而40μg/mL的水杨酸使三角褐指藻的油脂含量增加了87. 48%。     

原绿球藻的营养组分分析及饵料效果研究

为探究原绿球藻(Prochlorococcus marinus)的应用, 采用生化分析测定了其营养组分, 并进行了投喂蒙古裸腹溞和褶皱臂尾轮虫饵料效果试验. 结果显示: 原绿球藻干品中含粗蛋白42.32%, 粗脂肪11.47%, 碳水化合物15.11%和灰分17.48%. 含16种氨基酸, 总氨基酸含量为35.88 mg/g, 包括必需氨基酸8种 (占总氨基酸的37.54%); 粗脂肪中含13种脂肪酸, 其中不饱和脂肪酸8种(占粗脂肪总重的58.26%), 单不饱和脂肪酸(54.12%)含量较高, 而多不饱和脂肪酸含量较低(4.14%). 用原绿球藻投喂蒙古裸腹溞, 藻最佳浓度是400104 cells/mL, 溞世代净生殖率达4.33, 内禀增长率为0.23. 蒙古裸腹溞在用原绿球藻强化之后, 二十碳五烯酸(EPA)能有效富集, 浓度可达6.69%. 不同密度的原绿球藻饲喂对褶皱臂尾轮虫抱卵数和抱卵率均影响显著. 投喂藻密度在48-96h阶段以600104 cells/mL为佳, 而96-144h以400104 cells/mL为佳. 通过研究发现, 原绿球藻具有较好的营养价值和饵料效果, 但在蒙古裸腹溞和褶皱臂尾轮虫培养中, 仍建议与其他藻混合投喂.       

Effects of two Avtemia diets with different contents of polyunsaturated fatty acids on the lipid composition of larvae of Atlantic herring (Clupea harengus

Atlantic herring larvae ( Clupea harengus ) were fed two enriched Artemia diets with different contents of (n-3) highly unsaturated fatty acids (HUFA), one containing low levels of 20: 5(n-3) and no 22: 6(n-3), the other containing substantial levels of both 20: 5(n-3) and 22: 6(n-3). After 30 days of culture, fatty acid compositions of lipid classes in the heads, bodies and eyes of the larvae were analysed. Fish fed Artemia with the low (n-3) HUFA diet lacking 22: 6(n-3) had lower amounts of total (n-3)HUFA and, in particular, of 22:6(n-3) in individual phospholipids and total neutral lipids of heads, bodies and eyes as compared to fish fed Artemia with high levels of (n-3)HUFA. The amount of 22: 6(n-3) in the fatty acids of phosphatidyl-ethanolamine of eyes was particularly susceptible to dietary depletion. The implications of these findings are discussed, particularly in relation to dietary requirements for 22: 6(n-3) during development of neural tissue in predatory fish iarvae.     

Long chain polyunsaturated fatty acid production and partitioning to triacylglycerols in four microalgae

Gas chromatographic profiling of fatty acids was performed during the growth cycle of four marine microalgae in order to establish which, if any, of these could act as a reliable source of genes for the metabolic engineering of long chain polyunsaturated fatty acid (LC-PUFA) synthesis in alternative production systems. A high-throughput column based method for extraction of triacylglycerols (TAGs) was used to establish how much and at what stage in the growth phase LC-PUFAs partition to storage lipid in the different species. Differences in the time course of production and incorporation of docosahexaenoic acid (22:6n-3, DHA) and eicosapentaenoic acid (20:5n-3, EPA) into TAGs were found in the marine microalgae Nannochloropsis oculata (Eustigmatophyceae), Phaeodactylum tricornutum and Thalassiosira pseudonana (Bacillariophyceae), and the Haptophyte Pavlova lutheri. Differences were not only observed between species but also during the different phases of growth within a species. A much higher percentage of the total cellular EPA was partitioned to TAGs in stationary phase cells of N. oculata compared to P. tricornutum. Although P. tricornutum produces DHA it does not partition it to TAGs. Both T. pseudonana and P. lutheri produce EPA and DHA and partition these to TAGs during the stationary phase of growth. These two species are therefore good candidates for further biochemical and molecular analysis, in order to understand and manipulate the processes that are responsible for the incorporation of LC-PUFAs into storage oils.     

Nonspecific immune response of rainbow trout (Oncorhynchus mykiss Walbaum) in relation to different status of vitamin E and highly unsaturated fatty acids

This study was designed to examine the effects of dietary vitamin E (VE) on modulation of immune responses when supplied with two levels of n-3 highly unsaturated fatty acids (n-3 HUFA) in rainbow trout, Oncorhynchus mykiss. Six semipurified diets were prepared containing three levels of dietary VE (0, 100 or 1000 mg alpha-tocopheryl acetate kg(-1) diet) and n-3 HUFA either at 20 or 48% of dietary lipid provided from fish oil or docosahexaenoic acid (DHA) concentrated fish oil respectively. The diets were fed to rainbow trout (100 g initial mean weight) for 15 weeks. The VE, vitamin C (VC) content in plasma and tissues and the nonspecific immune responses, both humoral (alternative complement activity, total immunoglobulin) and cellular (phagocytosis, nonspecific cytotoxicity) were examined. VE contents in the kidney reflected the dietary input but were lower in fish fed 48% n-3 HUFA diets, and could have impaired some of immune responses compared to fish fed 20% n-3 HUFA. VC contents in kidney followed the same pattern as VE. Both humoral and cellular immune functions deteriorated in fish fed VE deficient diets whereas improvement in most of the parameters corresponded to its supplementation. However, the higher dose of dietary VE did not substantially enhance the responses assayed compared to the 100 mg dose. Besides clearly indicating the role of VE in maintaining the immune functions in fish in relation to dietary n-3 HUFA, this study has revealed that optimum health benefits could be achieved when VE is maintained slightly above the levels generally recommended for normal growth.     

再投喂鱼油对瓦氏黄颡鱼肌肉脂肪酸组成的影响

为研究植物油替代鱼油对瓦氏黄颡鱼（Pelteobagrus vachelli）生长及肌肉脂肪组成的影响及重投喂鱼油对瓦氏黄颡鱼肌肉脂肪酸组成的影响,实验以大豆油分别替代饲料中的0（FO）、50（S1）、75（S2）和100%（SO）的鱼油配制等氮、等能的颗粒饲料,每组设置3个平行,养殖80d后,再投喂鱼油30d。结果表明,饲料中添加豆油不会显著影响瓦氏黄颡鱼的增重率、肝体指数和体成分（P>0.05）。随着饲料中大豆油含量的增加,S2和SO组肌肉中C18:1n-9、C18:2n-6和单不饱和脂肪酸比例显著增加（P < 0.05）,而C20:5n-3,C22:5n-3及n-3/n-6比例显著下降（P < 0.05）。再投喂鱼油30d后,SO组肌肉中C18:3n-6、C20:4n-6、Σ n-9、Σ n-6和S2组中C18:1n-9、Σ n-6比例显著下降（P < 0.05）,而S2和SO组肌肉中Σn-3多不饱和脂肪酸、C20:5n-3和C22:5n-3比例显著增加（P < 0.05）。在生产中,可采用先植物油饲料、后鱼油饲料的养殖方式提高瓦氏黄颡鱼肌肉品质（增加有益人类健康的多不饱和脂肪酸）。     

Influence of dietary conjugated linoleic acid (CLA) on lipid and fatty acid composition in liver and flesh of Atlantic salmon (Salmo salar)

The aim of the present study was to determine the effects of conjugated linoleic acid (CLA) on lipid and fatty acid metabolism in Atlantic salmon. The overall objective being to test the hypotheses that CLA has beneficial effects in salmon including growth enhancement, improved flesh quality through decreased adiposity and lipid deposition thereby minimising detrimental effects of feeding high fat diets, and increased nutritional quality through increased levels of beneficial fatty acids including n-3 highly unsaturated fatty acids (HUFA) and CLA itself. Salmon smolts were fed diets containing two levels of fish oil (low, approximately 18% and high, approximately 34%) containing three levels of CLA (a 1:1 mixture of 9-cis,trans-11 and trans-10,cis-12. at 0, 1 and 2% of diet) for 3 months and the effects on growth performance, liver and muscle (flesh) lipid contents and class compositions, and fatty acid compositions determined. The diets were also specifically formulated to investigate whether the effects of CLA, if any, were more dependent upon absolute content of CLA in the diet (as percentage of total diet) or the relative level of CLA to other fatty acids. Dietary CLA in salmon smolts had no effect on growth parameters or biometric parameters. However, there was a clear trend of increased total lipid and triacylglycerol contents in both liver and flesh in fish fed CLA, particularly in fish fed the high oil diets. Finally, CLA was incorporated into tissue lipids, with levels in flesh being 2-fold higher than in liver, but importantly, incorporation in liver was at the expense of saturated and monounsaturated fatty acids whereas in flesh it was at the expense of n-3HUFA.     

Effect of diets enriched in Delta6 desaturated fatty acids (18:3n-6 and 18:4n-3), on growth, fatty acid composition and highly unsaturated fatty acid synthesis in two populations of Arctic charr (Salvelinus alpinus L.)

This study aimed to test the hypothesis that diets containing relatively high amounts of the Delta6 desaturated fatty acids stearidonic acid (STA, 18:4n-3) and gamma-linolenic acid (GLA, 18:3n-6), may be beneficial in salmonid culture. The rationale being that STA and GLA would be better substrates for highly unsaturated fatty acid (HUFA) synthesis as their conversion does not require the activity of the reputed rate-limiting enzyme, fatty acid Delta6 desaturase. Duplicate groups of two Arctic charr (Salvelinus alpinus L.) populations with different feeding habits, that had been reported previously to show differences in HUFA biosynthetic capacity, were fed for 16 weeks on two fish meal based diets containing 47% protein and 21% lipid differing only in the added lipid component, which was either fish oil (FO) or echium oil (EO). Dietary EO had no detrimental effect on growth performance and feed efficiency, mortalities, or liver and flesh lipid contents in either population. The proportions of 18:2n-6, 18:3n-3, 18:3n-6, 18:4n-3, 20:3n-6 and 20:4n-3 in total lipid in both liver and flesh were increased by dietary EO in both populations. However, the percentages of 20:5n-3 and 22:6n-3 were reduced by EO in both liver and flesh in both strains, whereas 20:4n-6 was only significantly reduced in flesh. In fish fed FO, HUFA synthesis from both [1-(14)C]18:3n-3 and [1-(14)C]20:5n-3 was significantly higher in the planktonivorous Coulin charr compared to the demersal, piscivorous Rannoch charr morph. However, HUFA synthesis was increased by EO in Rannoch charr, but not in Coulin charr. In conclusion, dietary EO had differential effects in the two populations of charr, with HUFA synthesis only stimulated by EO in the piscivorous Rannoch morph, which showed lower activities in fish fed FO. However, the hypothesis was not proved as, irrespective of the activity of the HUFA synthesis pathway in either population, feeding EO resulted in decreased tissue levels of n-3HUFA and 20:4n-6. This has been observed previously in salmonids fed vegetable oils, and thus the increased levels of Delta6 desaturated fatty acids in EO did not effectively compensate for the lack of dietary HUFA.     

Antioxidant defense of rainbow trout (Oncorhynchus mykiss) in relation to dietary n-3 highly unsaturated fatty acids and vitamin E contents

This study examined the modulation of the antioxidant status and related physiological changes in rainbow trout Oncorhynchus mykiss under different levels of dietary n-3 highly unsaturated fatty acids (n-3 HUFA) and vitamin E. Six diets containing 0, 100 or 1000 mg alpha-tocopheryl acetate kg(-1) diet and 20% or 48% n-3 HUFA provided by normal fish oil or DHA concentrated fish oil, respectively, were fed to 100 g size fish for 15 weeks. Growth of fish fed vitamin E deficient diets under both levels of n-3 HUFA were slightly retarded, accompanied by a reduction of hematocrit values, an enlargement of liver and spleen, an elevation of lipid hydroperoxide in red blood cell and the antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase). Supplementation of vitamin E could protect the fish from these adverse effects; however the higher dose was no better compared to the moderate dose. The modulations were clearly seen in fish fed high n-3 HUFA (48%) since they were under greater oxidative stress as indicated by the markers, lipid hydroperoxide and 8-isoprostane. The increased activity of enzymes corresponds to physiological mechanisms combating the elevation of free radicals under oxidative stress and a dietary fatty acid profile-dependent moderate dose of vitamin E is all that is required to function as an effective antioxidant.     

Effects of dietary n-3 highly unsaturated fatty acids on growth, nonspecific immunity, expression of some immune related genes and disease resistance of large yellow croaker (Larmichthys crocea) following natural infestation of parasites (Cryptocaryon irritans)

The study was conducted to investigate the effects of dietary n-3 highly unsaturated fatty acid (n-3 HUFA) on growth, nonspecific immunity, expression of some immune related genes and disease resistance of juvenile large yellow croaker (Larmichthys crocea) following natural infestation of parasites (Cryptocaryon irritans). Six isoproteic and isolipidic diets were formulated with graded levels of n-3 HUFA ranging from 0.15% to 2.25% of the dry weight and the DHA/EPA was approximately fixed at 2.0. Each diet was randomly allocated to triplicate groups of fish in floating sea cages (1.0 × 1.0 × 1.5 m), and each cage was stocked with 60 fish (initial average weight 9.79 ± 0.6 g). Fish were fed twice daily (05:00 and 17:00) to apparent satiation for 58 days. Results showed that moderate n-3 HUFA level (0.98%) significantly enhanced growth compared with the control group (0.15% HUFA) (P < 0.05), while higher n-3 HUFA levels (1.37%, 1.79% and 2.25%) had detrimental effects on the growth though no significance was found (P > 0.05). Nitro blue tetrazolium (NBT) positive leucocytes percentage of head kidney and serum superoxide dismutase (SOD) activity increased with increasing n-3 HUFA from 0.15% to 0.60%, and decreased with further increase of n-3 HUFA from 0.60% to 2.25% (P < 0.05). Serum lysozyme activity increased significantly as n-3 HUFA increased from 0.15% to 1.37%, and then decreased with n-3 HUFA from 1.37% to 2.25% (P > 0.05). There were no significant differences in phagocytosis index (PI) of head kidney leucocytes among dietary treatments (P > 0.05). The hepatic mRNA expression of Toll-like receptor 22 (TLR22) and Myeloid differentiation factor 88 (MyD88) was significantly up-regulated in fish fed the diets with low or moderate levels, while in kidney this increment was only found at specific sampling time during the natural infestation of parasites. The 13 d cumulative mortality rate following natural infestation of parasites decreased with n-3 HUFA increased from 0.15% to 0.60% (P < 0.05), and significantly increased with n-3 HUFA from 0.60% to 2.25% (P < 0.05). Results of this study suggested that fish fed low or moderate dietary n-3 HUFA had higher growth, nonspecific immune responses, expression levels of some immune related genes and disease resistance of large yellow croaker following natural infestation of parasites and dietary n-3 HUFA may regulate fish immunity and disease resistance by altering the mRNA expression levels of TLR22 and MyD88.     

Fatty acid composition and lipid peroxidation of soft-shelled turtle, Pelodiscus sinensis, fed different dietary lipid sources

Juvenile soft-shelled turtles (Pelodiscus sinensis) were fed 7 diets containing 8% of lard, soybean oil, olive oil, menhaden fish oil, or mixtures of 1 to 1 ratio of fish oil and lard, soybean oil, olive oil for 10 weeks. Growth and muscle proximate compositions of the turtles were not affected by different dietary treatments (p>0.05). Fatty acid profiles in muscle polar lipids, muscle non-polar lipids, and liver polar lipids reflected the fatty acid composition of dietary lipid source. Turtles fed diets containing fish oil generally contained significantly higher (p<0.05) proportion of highly unsaturated fatty acids (HUFA) in both polar and non-polar lipids of muscle and polar fraction of liver lipids than those fed other oils. Non-polar fraction of liver lipids from all groups of turtles contained less than 1% of HUFA. All turtles contained relatively high proportions of oleic acid in their lipids regardless of the dietary lipid source. Further, lipid peroxidation in both muscle tissue and liver microsomes of turtles fed fish oil as the sole lipid source was greater (p<0.05) than those fed fish oil-free diets. Turtles fed olive oil as the sole lipid source had the lowest lipid peroxidation rate among all dietary groups. The results indicate that dietary n-3 HUFA may not be crucial for optimal growth of soft-shelled turtles although they may be used for metabolic purpose. Further, high level of dietary HUFA not only increases the HUFA content in turtle tissues, but also enhances the susceptibility of these tissues to lipid peroxidation.