莫荷罗非鱼幼鱼耐盐性能的初步研究

以橙色莫桑比克罗非鱼与荷那龙罗非鱼的杂交子代莫荷罗非鱼(Oreochromis mossambicus♀×O.hornurum♂)为实验材料,通过急性耐盐实验和慢性耐盐驯化实验,对其幼鱼耐盐性进行了初步研究。结果表明:莫荷罗非鱼的96 h半致死盐度为(33.74±0.94)‰;在每天将盐度提高8‰的情况下,其半致死盐度为(112.93±4.87)‰,驯化致死盐度为128‰~136‰。实验表明,莫荷罗非鱼经过驯化可以耐受更高盐度的水环境,具有在海水中养殖的潜力。     

橙色莫桑比克罗非鱼（Oreochromis mossambicus）和荷那龙罗非鱼（O．hornorum）的选育效果评价

以橙色莫桑比克罗非鱼（Oreochromis mossambicus）和荷那龙罗非鱼（O．hornorum）为基础群体，分别对其进行选育，并对产生的选育系F4代的选育效果进行了评价。经过4代的选育，橙色莫桑比克罗非鱼和荷那龙罗非鱼的日增重率分别比对照系提高了27．96％和36．73％，差异显著（P〈0．05），平均每代选育效应分别为6．99％和9．18％。F4代的体重变异系数分别为23．74％和22．17％，比对照组分别降低了24．83％和36．33％。而且第一次性成熟时这2种罗非鱼的平均体重都比对照系增加2倍以上，其杂交子代的雄性率达到了99．4％。试验结果表明，橙色莫桑比克罗非鱼和荷那龙罗非鱼的选育效果明显，F4代的生长性能有了显著提高，个体之间的生长速度趋于一致；也说明这2种罗非鱼F4代仍具有一定的选育潜力，对其继续进行选育是切实可行的。     

罗非鱼催乳素Ⅰ基因的组织分布及盐胁迫对其表达的影响

采用同源克隆方法从橙色莫桑比克罗非鱼（Oreochromis mossambicus）、荷那龙罗非鱼（O.hornorum）及其正反交子代垂体中克隆了催乳素Ⅰ基因（PRLⅠ）,并对其核苷酸序列和推导的氨基酸序列进行了比对分析。结果显示,4种罗非鱼的PRLⅠ基因序列长度均为798 bp,ORF长639 bp,共编码212个氨基酸;橙色莫桑比克罗非鱼和荷那龙罗非鱼仅在31号位点存在一个氨基酸残基差异。用q PCR方法分析橙色莫桑比克罗非鱼和荷那龙罗非鱼PRLⅠ基因在不同组织或器官中的表达,结果表明罗非鱼PRLⅠ基因在垂体中的表达量最高,在其他组织中的表达量较低;盐胁迫后4种罗非鱼垂体中的PRLⅠmRNA水平均显著降低,而在其他组织中的表达变化不大。由此可知PRLⅠ基因主要在垂体表达,参与罗非鱼的渗透压调节。     

荷那龙罗非鱼、橙色莫桑比克罗非鱼及其杂交F1呼吸耗氧率的初步研究

用呼吸室法对荷那龙罗非鱼、橙色莫桑比克罗非鱼及其杂交F1的呼吸耗氧率、窒息点进行了试验。试验结果表明:①水温为16~32℃时,平均体重为10.40~116.28 g的荷那龙罗非鱼的耗氧率在0.07~0.61 mg/g.h,平均体重为18.98~102.53 g的橙色莫桑比克罗非鱼的耗氧率范围是0.06~0.43 mg/g.h,平均体重2.24~133.82 g的杂交F1莫荷鱼的耗氧率范围是0.06~0.65 mg/g.h;3种试验鱼的耗氧率随着温度的升高而增加;耗氧率与鱼体规格呈负相关。②3种实验鱼的耗氧率均为白天高于夜间。③水温24℃时,3种试验鱼的溶氧临界窒息点分别是:荷那龙罗非鱼0.33~0.55 mg/L,橙色莫桑比克罗非鱼0.24~0.31mg/L,莫荷鱼为0.38~0.43 mg/L。     

橙色莫桑比克罗非鱼和荷那龙罗非鱼的染色体核型分析

采用体腔注射PHA-空气干燥法对橙色莫桑比克罗非鱼(Oreochromis mossambicus)和荷那龙罗非鱼(O.hornorum)染色体数量、形态和核型进行了分析和比较。结果显示:两种罗非鱼的二倍体染色体数目均为2n=44,都具有1对特大的染色体,未发现中部着丝粒染色体对和异型染色体。两种罗非鱼的染色体组型形态基本相似,它们的核型公式为2n=44,6sm+24st+14t,NF=50,用常规染色体染色的方法难以区分。研究结果表明,这两种罗非鱼的常规核型差异不显著,在分类地位上非常接近。     

慢性盐度胁迫对吉丽罗非鱼(尼罗罗非鱼♀×萨罗罗非鱼♂)及其两亲本耐盐性的影响

为深入研究养殖新品种吉丽罗非鱼[尼罗罗非鱼(♀)×萨罗罗非鱼(♂)]的耐盐性能,对吉丽罗非鱼及其两个亲本尼罗罗非鱼和萨罗罗非鱼进行了慢性盐度胁迫实验,分析了3种罗非鱼耐盐性能的差异,建立了盐度胁迫过程中死亡率与致死盐度及时间的回归模型,结果显示:(1)3种罗非鱼的耐盐能力差异显著,吉丽罗非鱼的耐盐性能接近于萨罗罗非鱼,远高于尼罗罗非鱼,耐盐胁迫时3种罗非鱼的平均致死盐度分别为57.9、66.7和18.5.(2)盐度胁迫实验中尼罗罗非鱼个体间死亡时间差异最大,萨罗罗非鱼个体之间差异最小,吉丽罗非鱼介于其间;吉丽罗非鱼和萨罗罗非鱼死亡时间都有极显著的正态负偏移,离群值和极值较多,尼罗罗非鱼有较显著正态正偏移,只有离群值,没有极值.(3)3种罗非鱼盐度胁迫实验中死亡率与死亡时间及盐度之间的回归关系更适合一元回归,吉丽罗非鱼盐度胁迫实验中死亡率(y)与死亡时间(t)的回归模型为增长模型Y=e (-7.694+0.031t)(R2=0.979),死亡率(Y)与盐度(s)的回归模型为二次模型Y =0.542-0.037s +0.001s2(R2=0.950).     

新引进萨罗罗非鱼与其它8种罗非鱼耐盐差异

以萨罗罗非鱼、尼罗罗非鱼、以色列红罗非鱼和奥利亚罗非鱼自交和双列杂交后代共9种罗非鱼为实验材料,通过耐盐致死实验、半致死盐度实验和慢性耐盐驯化实验,对萨罗罗非鱼与其他几种罗非鱼耐盐生态特点的差异进行了比较分析,结果表明,(1)萨罗罗非鱼MST为(9.24±1.353)h,ST50为(6.20±1.235)h,MLS-96理论值为30.2,观察值为31.2,远高于另外8种罗非鱼。(2)根据耐盐能力,9种罗非鱼可分为4类:第一类是萨罗罗非鱼,耐盐极强,各项耐盐指标都远高于其他罗非鱼;第二类是以色列红罗非鱼和尼罗罗非鱼♀×奥利亚罗非鱼♂,耐盐强,离差值为正值;第三类是奥利亚罗非鱼、尼罗罗非鱼♀×以色列红罗非鱼♂、以色列红罗非鱼♀×尼罗罗非鱼♂、尼罗罗非鱼♀×奥利亚罗非鱼♂和奥利亚罗非鱼♀×尼罗罗非鱼♂,耐盐较强,离差值为负值;第四类是尼罗罗非鱼,耐盐较弱。(3)当进行慢性耐盐驯化时,萨罗罗非鱼在5d内,死亡率由0达到30%,以后缓慢增长,14～15d有个死亡率的高增长期,然后即进入缓慢增长期;第11天,盐度32.8时,死亡率达到50%,第39天,盐度为102时全部死亡。死亡率与驯化时间之间的线性回归关系为LnY=3...     

红罗非鱼海水养殖试验研究

红罗非鱼对盐度的适应范围较广，本试验将红罗非鱼由淡水中以５‰的盐度梯度逐步驯化到１７．５‰的海水中，成活率达１００％；其最佳生长盐度范围是５‰－１０‰，耐盐度可达３５‰，至４０‰盐度时出现死亡。在不同盐度水体中生长的红罗非鱼粗蛋白，粗脂肪含量顺序为：１７．５‰组＞１０‰组＞５‰组＞０‰。红罗非鱼和对虾混养，对虾成活率达８９．７％；红罗非鱼成活率为６２．６％，而日增重率达２．２６克／天。经测量和数理     

不同盐度下尼罗罗非鱼、萨罗罗非鱼和以色列红罗非鱼幼鱼生长、成活率及肥满系数的差异

用1m×1m×1m的实验网箱,在盐度分别为0、10、20及30的水体中进行尼罗罗非鱼(Oreochromisniloticus)、萨罗罗非鱼(Sarotherodonmelanotheron)和以色列红罗非鱼(Israeliredtilapia)幼鱼的养殖实验。结果表明:(1)盐度、鱼的种类及盐度-鱼类的交互作用都对3种罗非鱼的生长及体重变异系数有显著影响(P<0 05);3种罗非鱼的成活率和肥满系数只受鱼的种类影响(P<0 05);盐度、盐度-鱼类的交互作用对其都无显著影响。(2)生长和盐度之间的回归关系在尼罗罗非鱼和以色列红罗非鱼较显著,在萨罗罗非鱼显著性较差。(3)尼罗罗非鱼和以色列红罗非鱼的生长随着盐度的降低而加快,萨罗罗非鱼的生长随着盐度的降低而减慢。在3种鱼中,盐度在6 9以下时,尼罗罗非鱼生长最快;盐度7 4～28 7时,以色列红罗非鱼生长最快;盐度高于29 0时,萨罗罗非鱼生长最快。(4)在实验的4种盐度下,萨罗罗非鱼的成活率都高于以色列红罗非鱼和尼罗罗非鱼,而除了在淡水中外,以色列红罗非鱼的成活率又都高于尼罗罗非鱼;萨罗罗非鱼的肥满系数都显著高于尼罗罗非鱼和以色列红罗非鱼,而以色列红罗非鱼的肥满系数和尼罗罗非鱼的没有显著差异。     

以色列红罗非鱼耐盐性的初步研究

设计 0‰、15‰、2 5‰和 32‰四种盐度梯度 ,对引进的以色列红罗非鱼的仔鱼、稚鱼和幼鱼的耐盐性进行了初步研究。结果表明 ,在 32‰的海水中 ,以色列红罗非鱼的耐盐指标分别为 :仔鱼 ,MST为2 .6 8h ,ST5 0为 3.6h ,MLS 96为 17‰ ,BT为 0 .5h ,死亡率为 10 0 % ;稚鱼 ,MST为 2 .1h ,ST5 0为 2 4 .6h ,MLS 96为 2 0‰ ,BT为 0 .6 7h ,死亡率为 10 0 % ;幼鱼 ,MST为 14 .8h ,ST5 0为 4 0h ,MLS 96为 2 1‰ ,BT为 5h ,死亡率为 10 0 % ;以色列红罗非鱼的耐盐性高于尼罗罗非鱼和奥利亚罗非鱼 ,低于佛罗里达红罗非鱼 ,与莫桑比克罗非鱼及其一些杂交种相似。以色列红罗非鱼的耐盐性与其日龄有关 ,日龄越大 ,其耐盐性越强。幼鱼与仔鱼、稚鱼间耐盐性存在极显著差异 ,仔鱼和稚鱼间耐盐性差异不显著。几种耐盐指标中 ,ST5 0最灵敏 ,MST和BT次之 ,MLS 96和死亡率较差     

Sex reversal in the genus Oreochromis: optimization of feminization protocol

Abstract. High rate of feminization was achieved by oral administration of diethylstilbestrol (DES) and ethynyloestradiol (EES) to gonadally undifferentiated Oreochromis mossambicus (L.) and O. mossambicus × O. urolepis hornorum Trewavas all-male hybrid. All-female groups were produced at doses > 10mg/kg DES and >50mg/kg EES, when fry immediately after yolk-sac absorption were fed hormone-treated feed ad libitum. The critical period for feminization was about one week. Treatments longer than 10 days did not result in a higher proportion of females, and treatments starting later than one week after yolk-sac absorption were not effective. Optimal derived protocol was applied to O. aureus (Steindachner), resulting also in complete feminization.     

Effect of Salinity on Hatching in Neobenedenia melleni, a Monogenean Ectoparasite of Seawater-Cultured Tilapia

Laboratory experiments were conducted to determine the effect of salinity on embryonic development and hatching in Neobenedenia melleni , a monogenean ectoparasite of seawater-cultured (37 ppt) Florida red tilapia ( Oreochromis urolepis hornorum × O. mossambicus ). Eggs, collected from adult monogeneans at 37 ppt, were exposed to different salinities (0, 6, 12, 18, 24, 30 and 37 ppt) for 48, 72 or 96 h. Varying degrees of post-treatment development and hatching occurred when natural seawater conditions were restored. Hatching success generally declined with decreasing salinity and increasing duration of exposure. Under all durations of exposure, hatching success remained relatively high (≥ 69.6%) at salinities of 24 ppt and above, but declined markedly (≤ 32.5%) at lower salinities. Hatching did not occur in eggs exposed to fresh water (0 ppt) for 72 and 96 h. The most effective treatments in preventing hatching, other than prolonged exposure to fresh water, were 96 h exposures to low-salinity brackish water. Percent hatch after 96 h exposure to 6, 12 and 18 ppt was 5.5, 11.9 and 5.8%, respectively.     

莫荷罗非鱼“广福1号”与其亲本间DNA甲基化的差异分析

为了探讨罗非鱼杂种优势形成过程中基因组DNA甲基化模式的变化,运用甲基化敏感扩增多态技术(methylation sensitive amplified polymorphism,MSAP)分析橙色莫桑比克罗非鱼、荷那龙罗非鱼及其杂交种莫荷罗非鱼"广福1号"的皮肤、肌肉和鳃等11种组织的DNA甲基化水平差异。采用16对引物进行选择性扩增,经聚丙烯酰胺凝胶电泳带型分析结果显示:莫荷罗非鱼"广福1号"及其亲本在不同组织间的甲基化水平存在组织特异性,相同组织不同亲、子代罗非鱼间的甲基化程度亦不同;橙色莫桑比克罗非鱼、荷那龙罗非鱼以及"广福1号"各组织平均总甲基化水平分别为32.21%、38.03%和29.77%,莫荷罗非鱼"广福1号"的甲基化水平低于双亲;与亲本相比,莫荷罗非鱼"广福1号"的甲基化模式除了大多数保持稳定遗传(A、B、C类型分别为19.67%、29.99%、25.42%)之外,24.92%胞嘧啶位点发生去甲基化和超甲基化,且去甲基化位点(E类型,15.73%)多于超甲基化位点(D类型,9.19%)。研究表明,莫荷罗非鱼"广福1号"基因组DNA的低甲基化特征和甲基化模式的重调可能与耐盐杂种优势有关。     

Effects of Thermal and Thermo-Haline Shocks on Survival and Osmotic Concentration of the Tilapias Oreochromis mossambicus and Oreochromis aureus × Oreochromis niloticus Hybrids

Abstract.— The effects of thermal and thermo/haline shocks on the tilapias Oreochromis mossambicus and O. aureus × O. niloricus hybrids were investigated. Fingerlings were transferred abruptly from 25 C fresh water to fresh water or salt water (26 ppt) maintaining temperatures of 15, 20, 30 and 35 C. In fresh water, fish survival was not affected by temperature shock, but they suffered from a chill coma and developed fungal infection at 15 C. In salt water, thermo-haline shock did not affect the survival of O. mossambicus , while the survival rates of tilapia hybrids were 6.7, 100, 100, 70 and 59.7% at 15, 20, 25, 30 and 35 C, respectively. Plasma osmotic concentrations of O. mossambicus transferred to 15 and 35 C salt water were quickly and sharply increased, but gradually decreased to lower levels. Osmotic concentrations of tilapia hybrids were also increased, but never returned to their initial (lower) levels over one week. This study revealed that these fishes are more tolerant to high rather than low temperature shocks and O. mossambicus are more resistant to thermo-haline shocks rather than tilapia hybrids. It also indicated that thermo-haline shocks should be minimized during fish transportation and acclimation.     

4种遗传型罗非鱼的耐盐慢性驯化表现

在实验室小水体中,对尼罗罗非鱼(Oreochromis niloticus,新吉富)、萨罗罗非鱼(Sarothrodon melanotheron)以及它们的杂交F1和F2("吉丽"罗非鱼)进行盐度梯度实验,观察其耐盐能力。采用4(遗传型)×4(水平或重复)随机区组设计。对照组全程维持淡水养殖;实验组起始盐度为0,盐度每天提高8直至实验鱼100%死亡。在水温保持(27.2±1.3)℃、正常投饵情况下,萨罗罗非鱼、尼罗罗非鱼、杂交F1及F2的50%死亡盐度平均值(MLS)分别为125.78±1.66、54.22±2.51、77.33±1.89和73.73±1.32;萨罗罗非鱼的累计存活率(CS)和MLS值均显著高于尼罗罗非鱼、杂交F1和F2(P<0.05);杂交F1和F2的CS值及MLS值均显著高于尼罗(P<0.05);F2和F1之间CS值和MLS值差异不显著(P>0.05)。     

Optimum Density of Red Tilapia Oreochromis mossambicus×O. urolepis hornorum in a Pulsed-Flow Culture System

Abstract.— Densities of 9 tilapia (hybrid Oreochromis mossambicus × O. urolepis hornorum)/m³ gave the highest production among five densities (1, 3, 6, 9, and 12 fish/m³) tested in a pulsed-flow culture system. Culture of fish in irrigation ditches may have great potential for integrating fish farming with irrigated agriculture. Each 1,000 meters of ditch could potentially produce up to 1,400 kg of tilapia during a 112-d growing season.     

Salinity tolerance of Nile tilapia fry (Oreochromis niloticus), spawned and hatched at various salinities

Fertilized eggs of the Nile tilapia (Oreochromis niloticus L.) spawned in freshwater, were removed from mouthbrooding females, 1 day post-spawning and artificially incubated at elevated salinities. At 6 days post-hatching, mean survivals of 85.5, 84.4, 82.5, 56.3, 37.9, 20.0 and 0% were recorded for broods incubated at salinities of 0, 5, 10, 15, 20, 25 and 32 ppt, respectively. Fertilized eggs exhibited a 96-h median lethal salinity (MLS-96) of 18.9 ppt, a value identical to that of 7- to 120-day-old fry and fingerlings. Fertilized eggs exhibited a higher median survival time (ST₅₀ = 978 min) than 7- to 395-day-old fry and fingerlings (ST₅₀ = 28.8–179.0 min).The salinity tolerances of fry spawned at various salinities and fry spawned in freshwater but hatched at various salinities, were determined using the median survival time (ST₅₀), mean survival time (MST) and 96 h-median lethal salinity (MLS-96) indices. For comparative purposes, fry spawned and hatched in freshwater were acclimatized to various salinities and their salinity tolerance determined. Fry salinity tolerance progressively increased with increasing salinity of spawning, hatching, or acclimatization. However, at equivalent salinity, early exposure (spawning) produced progeny of comparatively higher salinity tolerance than those spawned in freshwater and hatched at elevated salinity. Similarly, at equivalent salinity, progeny spawned in freshwater but hatched at elevated salinity exhibited higher salinity tolerance than those spawned and hatched in freshwater, then acclimatized to an elevated salinity.The utility of these methods of early salinity exposure toward the saltwater culture of tilapias is discussed.