不同养殖模式下雌核发育彭泽鲫雌雄鱼性别分化相关基因的表达差异

将同一批经雌核发育产生的F1彭泽鲫(Carassius auratus var.pengze)仔鱼(Pcc)分别置于实验室和池塘进行养殖,结果发现,与池塘养殖雄鱼比例极少相比,实验室养殖中出现了高比例的雄鱼。实验室养殖Pcc F1雄雌比例为(43.6±3.0)%,而池塘养殖Pcc F1雌雄比为(4.7±1.2)%。本研究比较了不同养殖模式下雌雄鱼性腺分化相关基因的表达,结果发现除Pcc-vasa、Pcc-esr1和Pcc-esr2b外,实验室养殖Pcc F1精巢中性腺分化、受体、类固醇合成酶类基因表达极显著(P0.01)或显著(P0.05)高于卵巢中对应基因的表达量。对于池塘养殖的Pcc F1,除Pcc-amh、Pcc-dmrt1b、Pcc-dmrt1c、Pcc-foxl2、Pcc-vasa和Pcc-esr2b外,精巢中性腺分化和受体基因表达极显著(P0.01)或显著(P0.05)高于卵巢中对应基因的表达量;但精巢中绝大部分类固醇合成酶类基因的表达量极显著低于卵巢(P0.01)。实验室和池塘养殖Pcc F1雌雄出现差异表达的基因主要是类固醇合成酶类及调控芳香化酶的转录因子,这些基因的差异表达可能与雌雄激素的合成或调控相关,从而导致不同养殖模式出现不同比例的雄鱼。     

Sox9和amh基因在雌、雄虹鳟和伪雄鱼各组织中的表达模式分析

本研究利用Real-time PCR分析和比较sox9与amh基因在雄、雌虹鳟Oncorhynchus mykiss及及其伪雄鱼各组织中的表达模式。结果表明:sox9基因在这三种鱼性腺、脑、脾、肝以及脑垂体中的表达显著高于其他组织(P0.05)。在性腺组织中,sox9基因在雄鱼中的表达量显著高于伪雄鱼(P0.01),而在伪雄鱼中的表达量又显著高于普通雌鱼(P0.01)。脑组织中,雌鱼sox9的表达显著高于雄鱼和伪雄鱼(P0.05)。Amh基因在性腺和脑组织中的表达显著高于其他组织(P0.05)。该基因在伪雄鱼性腺和脑中的表达均显著高于雄鱼和雌鱼(P0.05)。结果表明,外源雄激素的诱导可导致伪雄虹鳟性腺和脑组织中sox9和amh基因的表达显著高于雌性虹鳟,促进其性腺的雄性化发育。本研究可为全雌性虹鳟制种技术研究奠定重要理论基础。     

基于天然XY雌鱼培育YY超雄尼罗罗非鱼的新方法

前期报道了利用尼罗罗非鱼LG22上性别连锁的分子标记检测到养殖群体存在天然XY雌鱼，但其能否用于培育YY超雄罗非鱼尚不清楚。本研究首先引入遗传性别受LG22染色体严格控制的CQ尼罗罗非鱼群体和具有天然XY雌鱼的WC群体，将CQ群体XY雄鱼与WC XY雌鱼杂交，检验杂交F1 YY超雄鱼是否可用于控制后代性别，并比较杂交F1 XY和YY罗非鱼体质量、性腺指数、血清激素水平和性腺基因表达情况。研究发现，CQ XY雄鱼和WC XY雌鱼交配，获得的F1 中具有25%的YY超雄鱼，经鉴定为全雄且可育。将F1 YY超雄鱼与WC XX雌鱼、WC XY雌鱼（母本）、杂交F1 XX雌鱼和CQ XX雌鱼交配，后代几乎全雄，仅在与F1 XX雌鱼交配后代中有2尾雌鱼（雄性率98%）。在孵化后180 d，杂交F1中XY和YY个体的体重、性腺指数、血清激素水平差异不显著。基因表达分析发现，YY鱼精巢中AmhX/AmhY mRNA表达显著高于XY鱼，而Dmrt1 和Cyp11b2 mRNA表达水平差异不显著。杂交F1 YY和XY鱼生理指标无明显差异。因此，采用尼罗罗非鱼天然XY雌鱼能够培育YY超雄鱼，且该YY超雄鱼能够用于罗非鱼性别控制。     

辛基酚对鲤的雌激素效应

研究了辛基酚对鲤的雌激素效应。经10、50、100、300和500μg/L辛基酚暴露32d后,鲤存活率和肥满度与对照组无差异;性腺指数变化明显,雌鱼性腺指数随暴露剂量的增大而增大,雄鱼性腺指数随暴露剂量的增大而减小;50μg/L及以上暴露组与对照组差异显著(P<0.05)。辛基酚能诱导鲤雄鱼产生卵黄蛋白原,暴露剂量为10μg/L组有部分雄鱼肝脏匀浆和血液中检出卵黄蛋白原,50、100和300μg/L组卵黄蛋白原含量随辛基酚浓度的增大而显著增大,500μg/L组卵黄蛋白原含量低于300μg/L组、高于100μg/L组,均为极显著差异(P<0.01)。     

瓯江彩鲤配套选育系繁殖性状的配合力测定与杂交优势分析

以瓯江彩鲤(Cyprinus carpio var.color)5个配套选育系进行双列杂交产生的F1的数据为分析对象,利用统计学和数量遗传学方法对6个繁殖性状(雄鱼性腺指数、雌鱼性腺指数、绝对繁殖力、相对繁殖力、受精率和孵化率)进行了配合力测定和杂交优势分析。结果发现,不同组合间的繁殖性状存在较大差异,但以"麻花"作母本的交配组合的平均雌鱼性腺指数和孵化率最高,以"全红"作母本的交配组合的绝对繁殖力和相对繁殖力最高,以"粉花"作母本的交配组合的所有繁殖性状参数均较差;雌鱼性腺指数与绝对繁殖力、相对繁殖力之间均存在显著的表型相关(r=0.411～0.847,P=0.01～0.04),绝对繁殖力与相对繁殖力之间存在极显著的表型相关(r=0.847,P<0.01);雌鱼性腺指数、绝对繁殖力和相对繁殖力3个性状检测到显著的特殊配合力;通过遗传效应预测,10个杂交组合均存在特殊配合力与杂交优势预测值,其雄鱼性腺指数、雌鱼性腺指数、绝对繁殖力、相对繁殖力和孵化率的杂交优势与特殊配合力均呈极显著相关(r=0.959～0.985,P<0.01)。本研究结果为瓯江彩鲤配套系育种提供了参考数据。     

西伯利亚鲟不同性别与卵巢发育时期血液性类固醇激素的差异与判别分析

利用电化学发光免疫分析法(ECLIA)测定了人工养殖西伯利亚鲟(Acipenser baerii baerii)不同性别和卵巢发育时期血浆中睾酮(T)和雌二醇(E2)的含量。利用活组织取样的方法,根据性别和卵子颜色及大小将实验鱼分为成熟雄鱼(M)、雌鱼Ⅲ期、Ⅳ期和Ⅴ期共4个组。研究结果表明,西伯利亚鲟血浆T含量雄鱼高于雌鱼(P<0.01),且雄鱼与雌鱼Ⅲ期和Ⅴ期组有极显著性差异(P<0.01),而E2含量除与雌鱼Ⅳ期有极显著性差异外(P<0.01),与雌鱼Ⅲ期和Ⅴ期组无显著性差异(P>0.05),雄鱼表现为T含量和T/E2比值高,而E2含量低。雌鱼随卵巢的发育T和E2含量均表现为"先上升,后下降"的趋势,即Ⅳ期组性类固醇激素的含量明显高于Ⅲ期和Ⅴ期,且差异极显著(P<0.01)。根据血浆中T和E2的含量建立了西伯利亚鲟性别和性腺发育时期的4个判别函数:YM=-11.322+0.043T+0.153E2,YⅢ=-1.390+0.000T+0.061E2,YⅣ=-18.074+0.032T+3.305E2,YⅤ=-2.316+0.785T+0.008E2,经检验总体判别准确率为95%,其中对性别的判别准确率为100%,对雌鱼卵巢发育时期的判别准确率为93%。     

尼罗罗非鱼雌雄鱼肌肉组织差异表达基因的筛选

应用引物退火控制技术(ACP)筛选尼罗罗非鱼雌雄鱼肌肉组织差异表达基因,寻找与雌雄鱼肌肉生长发育相关的候选基因。本实验从同等条件下养殖的尼罗罗非鱼群体中随机选取雌、雄鱼各5尾组成RNA池,采用引物退火控制技术,分析了两组个体肌肉组织差异表达基因。利用20对随机引物差异显示扩增,共获得8条ESTs,其中5个已知的ESTs分别为转录变体3(LOC100691543)、60S核糖体蛋白(RL3)、小白蛋白β样蛋白、肌型肌酸激酶M2-CK和转录因子Sox4,其余3个为未知的ESTs。实时定量PCR分析各差异表达基因在尼罗罗非鱼雌雄肌肉组织中的表达发现,8个差异表达基因中转录变体3与ACP6-Y在尼罗罗非鱼雄鱼肌肉组织中的表达均极显著高于雌鱼(P0.01),ACP3-X、60S核糖体蛋白(RL3)、小白蛋白β样蛋白、ACP15-X、肌型肌酸激酶M2-CK与转录因子Sox4在尼罗罗非鱼雌鱼肌肉组织中的表达均极显著高于雄鱼(P0.01)。结果表明,应用引物退火控制技术筛选获得了8个可能参与了雌雄鱼肌肉生长发育调控的ESTs,为进一步筛选雌雄鱼肌肉生长发育相关候选基因奠定了基础。     

配合饲料替代杂鱼对中华绒螯蟹生长发育、体成分及脂肪酸组成的影响

通过分别投喂配合饲料和天然杂鱼,研究配合饲料替代杂鱼对中华绒螯蟹生长发育、体成分及脂肪酸组成的影响。试验池塘设在上海市崇明县水产技术推广站特色水产养殖基地,每种饵料设3个平行。试验时间为2010年4月至11月,养殖结束后统计各试验组的存活率、体质量、产量,并随机取样测定各试验组雌雄蟹的肝胰腺指数、性腺指数、出肉率,同时测定肝胰腺、性腺和肌肉中水分、总脂、粗蛋白含量及脂肪酸组成。结果显示,杂鱼组和配合饲料组蟹的存活率、体质量、肝胰腺指数、性腺指数、出肉率等指标均无显著差异(P>0.05);杂鱼组雌雄蟹肝胰腺及雄蟹肌肉中水分含量极显著高于配合饲料组(P<0.01);杂鱼组雌雄蟹肝胰腺、性腺及雌蟹肌肉中总脂含量均显著低于配合饲料组(P<0.05);杂鱼组雌雄蟹肝胰腺中粗蛋白含量均显著高于配合饲料组(P<0.05),但杂鱼组雌蟹卵巢中粗蛋白含量极显著低于配合饲料组(P<0.01)。配合饲料组雌蟹肝胰腺游离脂肪酸含量显著高于杂鱼组(P<0.05),磷脂含量杂鱼组显著高于配合饲料组(P<0.05);配合饲料组雌蟹卵巢和肌肉甘油三酯含量均显著高于杂鱼组(P<0.05或P<0.01),游离脂肪酸和磷脂含量则杂鱼组显著高于配合饲料组(P<0.05或P<0.01);雌蟹肌肉中胆固醇含量配合饲料组极显著高于杂鱼组(P<0.01)。两组饵料雄蟹肝胰腺各脂类组成无显著差异;精巢中甘油三酯及游离脂肪酸含量为杂鱼组显著高于配合饲料组(P<0.01),磷脂含量为杂鱼组显著低于配合饲料组(P<0.05);雄蟹肌肉胆固醇含量配合饲料组显著低于杂鱼组(P<0.05)。杂鱼组雄蟹肝胰腺和肌肉中LOA含量极显著或显著低于配合饲料组(P<0.01或P<0.05),而杂鱼组雄蟹肌肉中ARA含量显著高于配合饲料组(P<0.05);杂鱼组雌蟹卵巢中LNA、ARA和DHA的含量极显著或显著低于配合饲料组(P<0.01或P<0.05)。研究结果表明,适宜的配合饲料替代杂鱼全程养殖中华绒螯蟹成蟹对其生长发育无显著负面影响,而对其体成分组成及脂肪酸组成有一定影响。     

尼罗罗非鱼卵巢发育过程中性类固醇激素与卵黄蛋白原含量变化及Vtg mRNA 表达特征

通过组织切片、酶联免疫吸附及荧光定量PCR等方法,研究了尼罗罗非鱼(Oreochromis niloticus)卵巢发育过程中性类固醇激素(雌二醇E2、孕酮P)、卵黄蛋白原(Vtg)含量及Vtg mRNA相对表达水平变化规律。结果表明,尼罗罗非鱼性腺指数(GSI)与卵巢成熟发育间呈同步性变化,Ⅴ期达到峰值。血清中E2含量自卵巢Ⅱ期开始显著升高,Ⅳ期达到峰值,Ⅴ期后显著下降;血清P含量自卵巢Ⅱ期开始不断升高,Ⅴ期达到峰值,Ⅵ期显著下降;E2、P分别在卵巢成熟发育前期与后期发挥作用。肝中Vtg含量先升、后降,Ⅳ期达峰值;血清、卵巢中Vtg含量均自Ⅱ期开始增加,Ⅴ期达峰值,Ⅵ期显著降低;不同组织中Vtg含量变化与卵巢成熟发育间存在密切关联。肝中Vtg mRNA表达水平在Ⅲ期达到峰值,Ⅳ期后持续下调;卵巢中Vtg mRNA表达水平相对较低,Ⅴ期达到峰值;初步推测肝、卵巢同是尼罗罗非鱼Vtg合成部位,肝是Vtg合成的主要器官,在卵黄积累阶段最为活跃,而卵巢Vtg合成水平相对较低。     

17α-甲基睾酮对大口黑鲈生长及性腺发育的影响

为探索建立大口黑鲈(Micropterus salmoides)生理雄鱼诱导技术, 以出膜后 15 d 体长(15.1±0.09) mm 的大口黑鲈为研究对象, 分别使用含有 17α-甲基睾酮(MT)的日粮饲喂 60 d。饲料 MT 添加量分别为 0 mg/kg (MT0)、 50 mg/kg (MT50)和 100 mg/kg (MT100), 分析其对大口黑鲈生长、性别分化、性类固醇激素含量及性腺发育相关基因表达水平的影响。结果表明, MT50 和 MT100 组大口黑鲈的体长和体重均显著低于 MT0 组(P＜0.05), MT50 和 MT100 组的雄性率均为 100%, 显著高于 MT0 组(45%); 性腺组织切片显示, MT 诱导获得的生理雄鱼性腺结构与 MT0 组雄鱼相似。性类固醇激素测定结果显示, MT50 和 MT100 组生理雄鱼血清中雌二醇的含量均显著低于 MT0 组雌鱼(P＜0.05), MT50 组生理雄鱼睾酮的含量显著高于 MT100 组(P＜0.05), 与 MT0 组雌鱼无显著差异(P＜0.05)。 此外, 与 MT0 组雌鱼相比, MT50 和 MT100 组生理雄鱼性腺中 Dmrt1 和 Gsdf 基因的表达水平显著上调(P＜0.05), 而 Foxl2 和 Cyp19a1a 基因的表达水平显著下调(P＜0.05)。研究结果表明, MT 添加投喂能有效诱导出膜后 15 d 的雌性大口黑鲈转为生理雄性个体, 适宜添加量为 50~100 mg/kg。本研究为大口黑鲈全雌品种培育奠定了基础。     

文蛤红壳色选育系F_3的生长规律及模型

为检验文蛤(Meretrix meretrix)红壳色选育系F_3的生长性能,连续比较了同等养殖条件下选育系F_3和自然对照组CG的生长情况,并采用Von Bertalanffy、Gompertz、Logistic和Brody 4种非线性模型对文蛤红壳色选育系F_3的生长参数进行生长模型构建,以研究文蛤红壳色选育系F_3的生长规律。结果表明,文蛤红壳色选育系F_3在浮游期、稚贝中间培育期和塘口养殖期内的生长均显著快于对照组CG(P0.05),F_3的平均日生长率均大于CG,490日龄内F_3的壳长相对于CG平均增长率为34.05%。塘口养殖期间,6~9月是F_3生长最为快速阶段,且F_3较CG的粒重增长率在98.27%以上。文蛤红壳色选育系F_3的壳长和粒重之间遵循复合曲线Y=9.028×1.499W,R2=0.977。文蛤红壳色选育系F_3的壳长生长遵循Logistic生长模型,其在575日龄时出现快速生长,这为及时疏苗养殖提供了依据。     

Cloning,expression, and induction by 17-β estradiol (E<Subscript>2</Subscript>) of a vitellogenin gene in the white cloud mountain minnow <Emphasis Type="Italic">Tanichthys albonubes</Emphasis>

Vitellogenins (Vtgs), the precursors for the yolk proteins, are very important for the embryonic development of teleosts, and have also been studied extensively as biomarkers for environmental estrogenic mimics. The cDNA for a Vtg was isolated from the liver of the female white cloud mountain minnow (Tanichthys albonubes) by 3′- and 5′-RACE methods. It is 4,171 bp in full length, and encodes a putative protein of 1,326 amino acids. This putative Vtg, designated as wcmmVtg, contains complete portions of LVI and PV, but lacks the C-terminal half of LVII and thus belongs to type I vitellogenin. In addition to the liver of the female fish, wcmmVtg was also shown to be expressed in the ovary. During ovarian development, the mRNA expression of wcmmVtg in both the liver and ovary was continuously increased from the previtellogenic to late vitellogenic stages, but then decreased significantly at post-spawning stage. In the male fish, expression of wcmmVtg mRNA was induced in the liver by treatment with E₂ (10 and 100 ng/l) for 14 days. These results suggest that the Vtg originated from the ovary of the white cloud mountain minnow may also contribute to the accumulation of yolk proteins during oocyte growth, and that the male white cloud mountain minnow is sensitive to the estrogenic treatment in terms of Vtg mRNA expression, which could also be applied to monitor the environmental estrogenic mimics.     

In vitro effect of pituitary,interrenal and gonadal hormones on vitellogenin synthesis in primary hepatocyte cultures of Chalcalburnus tarichi

Vitellogenin (Vtg) is an important precursor yolk protein in egg‐laying vertebrates, including fish. The 17β‐oestradiol (E2) plays a crucial role in the Vtg synthesis; moreover, certain hormones can stimulate Vtg synthesis. We investigated the possible role of E2, carp recombinant growth hormone (crGH), insulin (Ins), progesterone (P4) and 11‐deoxycortisol (11‐DOC) hormones in Vtg synthesis on primary juvenile Chalcalburnus tarichi hepatocyte culture. The amount of Vtg in the medium was measured at 2‐day intervals using enzyme‐linked immunosorbent assay (ELISA). The hepatocytes were maintained in culture for more than 2 weeks without the addition of serum components. Vitellogenin localization was visualized with the immunofluorescence method in E2‐supplemented hepatocytes. Among hormones applied to the culture, only E2 had an influence on Vtg synthesis in a time‐dependent manner, while crGH, Ins, P4 and 11‐DOC had no effect. However, in hepatocytes stimulated with E2 in combination with P4, a lower Vtg production was seen compared with Vtg produced when hepatocytes were stimulated with E2 alone. P4 proved to have potentiating effects on co‐treatment with E2‐induced Vtg production. As a result, E2 and P4 are the most important hormones for Vtg synthesis in juvenile C. tarichi hepatocyte culture.     

池塘循环水槽养殖模式下吉富罗非鱼的生长及生理响应变化

为探讨在池塘循环水槽养殖模式下吉富罗非鱼不同养殖密度的生长特性和生理指标变化,评估吉富罗非鱼在池塘循环水槽养殖模式下的适宜养殖密度,以吉富罗非鱼为实验对象,设计传统池塘养殖模式放养密度5尾/m~2 (SD1组),池塘循环水槽养殖模式放养密度180尾/m~2 (SD2组)和270尾/m~2 (SD3组),比较各组吉富罗非鱼的生长性能,分析血液生化指标和肝脏HSP70 mRNA表达量的变化规律。结果显示,经过120 d的养殖,SD2组吉富罗非鱼终末体质量、特定生长率和绝对生长率显著高于SD1和SD3组。SD2和SD3组存活率、体质量差异系数和饵料系数低于SD1组。SD2组血清皮质醇、血清谷丙转氨酶、谷草转氨酶、溶菌酶水平和肝脏HSP70 mRNA的相对表达量在30 d时显著高于SD1组。SD3组血清皮质醇和葡萄糖水平在60 d后持续上升,120 d时显著高于SD1组,谷丙转氨酶、谷草转氨酶、溶菌酶水平和肝脏HSP70 mRNA的相对表达量在60、90 d时显著高于SD1组,甘油三酯在整个实验期显著低于SD1组。SD2组吉富罗非鱼在养殖前期受到环境胁迫,中后期适应环境;SD3组在养殖中后期受到环境胁迫,长期处于应激状态。吉富罗非鱼生长和血清生理指标,池塘循环水槽养殖吉富罗非鱼的适宜养殖密度为180尾/m~2,在该密度下罗非鱼能适应养殖环境,养殖效果优于传统养殖模式。     

池塘内循环养殖模式下不同营养水平饲料对建鲤生长性能及养殖效益的影响

为探讨池塘内循环养殖模式下不同营养水平饲料对建鲤(Cyprinus carpiovar)生长性能及养殖效益的影响,以常规池塘养殖营养水平饲料为对照,提高蛋白、脂肪含量,形成3个营养水平的试验饲料,其中粗蛋白水平分别为32%、34%、38%,粗脂肪水平分别为8%、10%、11%,分别记为F1、F2、F3组,每组设3个重复,在跑道池(22 m×5 m×2 m)中连续投喂初始平均体重为(85.26±0.98)g的建鲤幼鱼72 d。结果显示:饲料营养水平对建鲤的存活率、增重率、特定生长率和饲料系数无显著影响;F3组蛋白质效率显著低于F1、F2。饲料营养水平对建鲤肝体指数、肠体指数和肥满度无显著影响;F3组的空腔率显著低于F1组。对照组F1的养殖效益最高,随着饲料营养水平的提高,建鲤养殖效益下降。综上所述,在池塘内循养殖模式下,投喂蛋白含量在32%左右,脂肪含量在8%左右及适量限制性氨基酸的饲料,建鲤幼鱼生长性能和养殖效益最好。     

Beneficial co‐culture of jellyfish Rhopilema esculenta (Kishinouye) and sea cucumber Apostichopus japonicus (Selenka): implications for pelagic‐benthic coupling

This study investigated monthly changes of sedimentation and sediment properties in three different culture systems (ponds) – i.e. jellyfish Rhopilema esculenta monoculture (J), sea cucumber Apostichopus japonicus and jellyfish co‐culture (SJ) and sea cucumber monoculture (S) – to verify the feasibility of co‐culturing jellyfish and sea cucumbers. Results showed that jellyfish culture accelerated the settling velocity of total particulate matter (TPM). Average TPM settling velocities in the SJ (75.6 g m^?2 day^?1) and J (71.1 g m^?2 day^?1) ponds were significantly higher than that in the S pond (21.7 g m^?2 day^?1) from June to September during the jellyfish culture period. Average settling velocities of organic matter (OM), total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) in the SJ pond increased significantly by 3.0, 2.9, 3.3 and 3.8 times, respectively, compared with those in the S pond. Sediment contents of OM, TOC, TN and TP in the SJ and J ponds were significantly higher than those in the S pond during the jellyfish culture season. The specific growth rate of sea cucumbers feeding on SJ sediment was significantly higher than that of those feeding on S sediment. Co‐culturing sea cucumbers with jellyfish may help alleviate benthic nutrient loading due to the jellyfish and provide a secondary cash crop.     

All-male Tilapia Hybrids of Two Strains of Oreochromis niloticus

Hybridization between Nile tilapia Oreochromis niloticus (Local and Stirling University strains) and blue tilapia O. aureus was found to be a tool to produce monosex populations. In order to select a purebred that produces all- or nearly all-male hybrids with high productivity, O. niloticus females and their diploid gynogenetics (meiogynes and mitogynes) were hybridized with O. aureus males. The sex ratio of progenies was evaluated from inter- and intraspecific crosses of two strains of Nile tilapia. Single-pair matings and group spawns under hatchery conditions showed no deviation ( P > 0.01) from the expected sex ratio of intraspecific crosses among two strains of Nile tilapia. However, a higher proportion of male progenies in blue tilapia was observed in group spawns in pond ( P < 0.004) and hatchery conditions ( P < 0.01). Only the Stirling strain and mitogynes produced all-male progenies under laboratory conditions. There were significant differences ( P < 0.05) in growth among hybrid progeny groups, when gynogens and their regular O. niloticus (Local strain) females were crossed with O. aureus males. Six-month hybrid offspring from mitogyne female parents grew better than those from regular and meiogyne female broods.     

Effects of season, maturity, and sex on lipid class dynamics in largemouth bass (Micropterus salmoides Lacepede)

Abstract Factors that can influence changes in lipid class concentrations in specific tissues have not been reported for largemouth bass Micropterus salmoides. We investigated patterns of lipid composition by measuring seasonal levels of total lipid and major lipid classes in the muscle and liver tissues of juvenile and adult largemouth bass and gonad tissue of adults. Fish were collected in December, February, April and July to correspond with key stages of the sexual cycle. Total lipid concentrations were substantially greater in hepatic (32.8 [female] to 56.6 [male] mg. g^?1) and gonadal tissues (34.4 [F] to 204.0 [M] mg. g^?1) than in muscle (7. 5 [F] to 11.4 [M] mg. g^?1). Muscle lipid concentrations in juveniles were significantly higher (10.9 [F] and 11.4 [M] mg. g^?1) in summer than in winter in adult muscle tissue (8.6 [F] and 9.4 [MI mg. g^?1). A 44% increase in ovary lipid was observed from preparatory to prespawn stages, followed by a 78% decline after the spawn. Additionally, seasonal hepatic lipid concentrations were substantially higher in juveniles. Concentrations of lipid classes (free cholesterol [C], triacylglycerol [TAG], free-fatty acids [FFA], esterified cholesterol [CE] and phospholipid [PL]) of all tissue types varied significantly among season, sex, and maturity categories. Changes with all lipid classes in the ovary coincided with those occurring in total ovarian lipid. Mobilization and transport of TAG and PL from the liver to the ovary appeared to occur during gametogenesis. All class concentrations in juveniles were invariably higher in liver than in muscle, but seasonally variable among hepatic and gonad tissues of adults. Juvenile males showed slightly greater hepatic C concentrations than other groups. Muscle and hepatic C were generally higher in juveniles.