Genetic variation inferred from RAPD fingerprinting in three species of tilapia

This study used random amplified polymorphic DNA (RAPD) fingerprinting for estimating genetic variation and species differentiation in three species of tilapia. A 16-mer random primer generated RAPD markers ranging from 250 to 2400 base pairs (bp). Genetic similarity estimates obtained by pairwise comparisons based on the method of Nei and Li (1979) indicated high genetic similarity (mean genetic similarity (± sd), 0.73 (± 0.15) for Nile tilapia; 0.78 (± 0.12) for Mozambique tilapia; and 0.87 (± 0.07) for Aureus tilapia) within each of the tilapia species. The average interspecies genetic similarities obtained among the three species were 0.59 (± 0.07) for Mozambique/Nile tilapia, 0.46 (± 0.09) for Aureus/Nile tilapia and 0.38 (± 0.07) for Aureus/Mozambique tilapia pair. DNA profiles generated in each species of tilapia were unique. A total of 13 RAPD markers differentiating the three species of tilapia were detected. Our study presented RAPD markers as a new class of useful genetic markers for assessment of genetic diversity and species differentiation in tilapia.     

Genetic diversity of Nile tilapia populations revealed by randomly amplified polymorphic DNA (RAPD)

Genetic diversity of the Nile tilapia Oreochromis niloticus collected from the river Nile (Cairo, Assuit and Qena) and two Delta lakes (Burullus and Manzalla) in Egypt was examined by the analysis of randomly amplified polymorphic DNA (RAPD). Of 25 primers examined,21 primers produced 230 RAPD bands. The percentage of polymorphic bands in Manzalla (29.4%) and Burullus (24%) populations was low compared with Assuit (30.54%), Cairo (33.5%) and Qena (44.84%) populations. The highest percentage of polymorphic bands was observed in the Qena population,suggesting a greater potential for use in breeding programs. The molecular phylogenetic tree constructed by unweighted pair‐group method of analysis shows Manzalla and Burullus populations strongly linked and separate from the Assuit and Cairo populations, with Qena population as outgroup. The data serve as a baseline analysis of the current genetic diversity found among O. niloticus populations in Egypt.     

Genetic diversity and differentiation of Nile tilapia (Oreochromis niloticus) revealed by DNA microsatellites

To assess the genetic diversity of Nile tilapia Oreochromis niloticus, a total of 250 fish from five Egyptian populations were genotyped using six microsatellite markers. Heterozygosity and Wright's F‐statistics (F_IS, F_ST, and F_IT) were calculated to determine the genetic variation within and between these populations. Observed heterozygosities were in the range of 0.4 (Burullus) to 0.96 (Qena), with F_IS values ranging from 0.082 to 0.282. The mean F_ST showed that approximately 96.5% of the genetic variation was within‐population and 3.5% was among populations. Standard genetic distances were used to classify the five populations into two major groups. The deeper lotic river Nile populations of Assuit and Cairo formed one group and the shallow less lotic Delta lakes populations of Manzalla and Burullus formed the second group, with the upstream Nile Qena population being an outgroup. The findings from the current study help understanding of the broad‐scale population structuring of the Nile tilapia (O. niloticus) allowing the population groupings identified to act as potential sources of genetic variation. These populations could be included in future Marker‐Assisted‐Selection programs for economically desired production traits.     

尼罗非鲫和奥利亚非鲫线粒体DNA遗传差异的研究

以酶切MitochondrialDNA（mtDNA）技术检测了尼罗非鲫和奥利亚非鲫的mtDNA。测得两种鱼线粒体基因组的大小都约为16．83kb。在使用的6种酶中，只有PvuⅡ在所检测的15尾尼罗非鲫mtDNA上产生了多态片段，3尾鱼的mtDNA产生了4个片段，12尾鱼的mtDNA产生3个片段。而6种酶在所有15尾奥利亚非鲫中均未检到多态片段。比较两种鱼的mtDNA酶切片段，仅PvuⅡ的酶切结果有所不同，尼罗非鲫mtDNA上有3个或4个PvuⅡ位点，但奥利亚非鲫mtDNA上有5个位点，因此，PvuⅡ的酶切位点可作为鉴别它们的分子遗传标记。     

WY型罗非鱼的性别鉴定

以尼罗罗非鱼(Oreochromis niloticus)和奥利亚罗非鱼(O.aurea)为材料,进行WZ♀×XY♂、WZ♀×YY♂、WY×ZY♂、WY×YY♂杂交实验及其子代分析,确认WY型罗非鱼的性别为雌性。     

Management options for a more complete utilization of the biological fish production in Sri Lankan reservoirs

Abstract– Stock dynamics of the introduced tilapia Oreochromis mossambicus and co-occurring indigenous cyprinids were studied in a typical lowland reservoir in Sri Lanka. All species exhibited peaks in reproductive activity during the rainy seasons in November and May. O. mossambicus was estimated to grow to 14 cm in its first year and to 21 cm in its second. A high natural mortality ( M was found, both for the cyprinids ( M =1.3 yr⁻¹ to 4.7 yr⁻¹ over a range of species) and for O. mossambicus ( M = 1.9 yr^−l and 1.7 yr⁻¹ for females and males). The fishing mortality ( F ) of O. mossumbicus , estimated for the length range from 15.0 to 18.5 cm, was 5.5 yr⁻¹ for females and 4.7 yr⁻¹ for males. The total fish biomass was estimated at 1 829 kg/ha, with 128 kg/ha O. mossambicus and 1 098 kg/ha small pelagic cyprinids, mainly Amblypharyngodon melettinus . The total biological fish production was around 5 400 kg/ha/yr, with O. mossambicus and the small pelagic cyprinids accounting for 400 kg/ha/yr and 3 600 kg/ha/yr respectively. The commercial fishery yielded 242 kg/ha/yr (including 70% or 169 kg/ha/yr O. mossambicus ), indicating an incomplete utilization of the total biological fish production. It was concluded that there is scope for an approximately 100% increase of the total yield. Reimplementation of a 76 mm minimum mesh size, to prevent overfishing of O. mossambicus , is recommended as a management measure. Additional options are direct exploitation of the untapped resource of small pelagic cyprinids, or indirect exploitation by means of a culture-based fishery on Lates calcarifer , a controllable predator.     

Genetic improvement of farmed tilapias: Biochemical characterization of strain differences in Nile tilapia

Four African wild strains (Egypt, Ghana, Senegal and Kenya) and four established Asian farmed strains of Nile tilapia, Oreochromis niloticus (popularly known in the Philippines as Taiwan, Thailand, Singapore and Israel) were analysed electrophoretically at 30 protein loci to estimate genetic differences among the strains. All strains shared alleles at 14 monomorphic and 16 variable loci. Among the African strains, characteristic allele frequency differences were observed at AAT-1 ^* 46 for Ghana and Senegal, ADH ^* 83 for Kenya, ADH ^* 120 for Senegal, G3PDH-2 ^* 300 for Egypt, IDDH ^* 67 for Senegal, sMDH-1 ^* 120 for Kenya and SOD ^* 150 for Senegal. Genetic distance values among the strains revealed a clustering of the farmed strains with Egypt and Ghana O. niloticus, a slight separation of the Senegal strain and a larger separation of the Kenya strain. This profile may reflect the origins of the few founder populations of this species previously introduced to Asia. It also confirms the wider genetic divergence of the Kenya strain (O. niloticus vulcani) from the others studied here, which are all O. n. niloticus. Observed heterozygosities of the strains ranged from 0.026 to 0.071, with the African wild strains the lower values (mean Ho = 0.036) and the farmed strains the higher ones (mean Ho = 0.056). The implications of these results to the ongoing tilapia genetic improvement programme in the Philippines are discussed.     

罗非鱼无乳链球菌巢式PCR检测方法的建立

根据无乳链球菌(Streptococcus agalactiae)cfb基因序列,设计、合成2对引物,优化扩增条件,建立了快速高灵敏度鉴别无乳链球菌的巢式PCR方法。结果显示:使用该方法对罗非鱼(Oreochromis mossambicus)血液样品进行检测,可检测到活菌浓度为8.7×104CFU/m L的无乳链球菌。对采自广西地区受无乳链球菌感染的19份罗非鱼样品进行检测,18份可获得目的片段,扩增到的序列均为无乳链球菌cfb基因序列,检测准确度达到94.7%。     

Species-characteristic and subspecies-characteristic haemoglobins in some tilapiine fishes and a comparative study on their globin chains

Haemoglobins of ten tilapia species of the genera Oreochromis, Sarotherodon and Tilapia, three subspecies of the Nile tilapia, O. niloticus, and an artificial hybrid cross were analysed by isoelectric focusing aimed at characterizing the taxonomic value of these oxygen-binding molecules. Heterogeneous haemoglobin phenotypes were observed in haemolysate samples of all the fishes, and species-characteristic as well as subspecies-characteristic patterns could be identified. F1 hybrids were distinguishable from pure parental specimens. Globin chain studies by AU- and AUT-PAGE systems confirmed the heterogeneity and species specificity observed by isoelectric focusing of the tetrameric molecules. A total of eight different -chains and eight different -chains were detected by AU-PAGE and species-characteristic globin chain variants were shown to occur in almost all species. Globin chain profiles of hybrid specimens were characterized by the presence of all parental globin chain variants. © Rapid Science Ltd. 1998     

Production of heterozygous and homozygous clones in Nile tilapia

Production of heterozygous and homozygous clones of Nile tilapia (Oreochromis niloticus L.) was successfully carried out. An outbred clonal line was produced by cross-breeding between a viable mitotic gynogenetic female and male (recessive mutation in a sex determining gene). At the same time, an inbred clonal line was produced by gynogenetic reproduction (retention of 2nd polar body) using optimal pressure/heat shock treatments. The heterozygous and homozygous nature of the two types of clonal lines were checked and identified at the adenosine deaminase ADA* marker locus. A model for the large scale production of similar clones is presented. The possible implications of such clonal lines in genetic research and in the culture of Oreochromis spp. are discussed. © Rapid Science Ltd. 1998     

2种水温条件下罗非鱼体内氟苯尼考的药物动力学比较

采用药饵给药,药物剂量为10mg·kg^-1,比较研究了22和28℃水温条件下奥尼罗非鱼（Oreochromis niloticus×O．aureus）体内氟苯尼考的药物动力学。结果得出,22℃组和28℃组罗非鱼血浆的峰药浓度（Cmax）分别为4．46和3．90μg·mL^-1,达峰时间（Tmax）均为12h,消除半衰期（T1/2β）分别为10．03和8．12h,药-时曲线下面积（AUC）分别为86．68和72．44h·μg·mL^-1。相应条件下的肌肉Cmax分别为6．88和4．59μg·g^-1,Tmax均为12h,T1／2β分别为10．97和8．03h,AUC分别为112．71和73．66h·μg·g^-1。低温组罗非鱼血浆和肌肉中药物的T1／2β均长于高温组,前者分别比后者长1．91和2．96h,表明低温组罗非鱼体内药物的消除速度慢于高温组。虽然2个水温组血浆和肌肉中药物的Tmax相同,但低温组血浆、肌肉的Cmax和AUC均明显高于高温组,表明低温组罗非鱼吸收利用药物程度高于高温组。     

Enhancement of Monosex Hybrid Red Tilapia,Oreochromis mossambicus × O. niloticusProduction in Portable Canvas Tanks Through Mixed-Feeding Strategies

Abstract

The viability of mixed-feeding schedules utilizing low-and high-protein diets for the production of monosex hybrid red tilapia, Oreochromis mossambicus × O. niloticuswas evaluated. Male red tilapia juveniles (mean initial weight 16.8±0.08 g) stocked at a rate of 159 fish/m³ in canvas tanks (3.05m × 0.92m × 1.22m) were grown under five different feeding schedules for 24 weeks. Two schedules, using low (25%, A) and high (35%, B) dietary protein were designated as control. Three mixed-feeding schedules tested were: the feeding of 1 day of low protein diet followed by 3 days of high-protein diet (1A/3B); 2 days of low-protein diet followed by 3 days of high-protein diet (2A/3B); and 3 days of low-protein diet followed by 3 days of high-protein diet (3A/ 3B). Results showed that growth performance parameters, such as specific growth rate (% SGR), percent gain, and weight gain were significantly higher (P < 0.05) for fish maintained on the feeding schedule of 3A/3B. Similarly, the feed conversion ratio, protein efficiency ratio, and protein retention values were also significantly better for fish grown under this schedule. In terms of production, the 3A/3B feeding schedule also resulted in the highest total yield (kg/m³) and yield above 250 g. The 3A/3B feeding schedule resulted in a 10.1% protein saving relative to Diet B. These results suggest that a 3A/3B feeding schedule be adopted for the best biological and economical performance of red tilapia.     

Effects of sex ratio, stocking density and age of hybrid tilapia on seed production in concrete tanks in Saudi Arabia

The influence of sex ratio, stocking density and age of hybrid tilapia (Oreochromis niloticus X O. aureus) brood fish on seed production in concrete tanks were evaluated in 1992 and 1993. A sex ratio of 1:2 and 1:3 (male: female) and a density of 2 fish m-2 gave the best result with respect to number of seed female-1 day-1 and number of seed kg-1-1 female day-1. Maximum seed production female-1 day-1 was recorded for 3-year-old females and the minimum for 1-year-olds, but in terms of seed kg-1 female day-1 and seed m-2 day-1, 1-year-olds produced the maximum number of seed followed by 2-, 3- and 4-year-old females. Seasonal pattern in seed production was apparently influenced by season and temperature. From the first harvest on 21 April 1993 the production increased gradually, reaching a peak during the third harvest and a second peak during the sixth harvest. Thereafter seed production gradually decreased, reaching a minimum during the tenth harvest on 27 October 1993. No seed were found during the last harvest of 18 November 1993. Maximum production coincided with the highest water temperature of around 28°C.     

2种养殖模式罗非鱼肉品质的比较

文章分别对池塘和水库养殖的奥尼罗非鱼（Oreochromis niloticus♀×0．aureus♂）的营养成分、感官评分、理化性质及游离氨基酸组成进行比较分析。结果显示：1）池塘养殖罗非鱼的水分质量分数较低,粗蛋白质量分数较高,差异达显著水平（P〈0．05）;而粗脂肪、粗灰分和总糖质量分数没有显著差异（P〉0．05）。2）水库养殖罗非鱼总体感官评分优于池塘养殖。3）两者的熟肉率、蒸煮损失及肌红蛋白差异都不显著,而pH、滴水损失、贮存损失、肌内脂肪和肌原纤维断裂指数（MFI）差异均显著。4）肌肉中检测到了18种常见氨基酸,两者间的天冬氨酸、谷氨酸、丝氨酸、甘氨酸、丙氨酸质量分数有显著差异,其他氨基酸无显著差异;两者的必需氨基酸质量分数相近,而池塘养殖的鲜味氨基酸、甜味氨基酸及半必需氨基酸质量分数均显著高于水库养殖的。从总体上来看,水库养殖罗非鱼嫩度要优于池塘养殖,而在营养成分及鲜甜味方面不及池塘养殖。     

Effect of dietary betaine levels on growth performance and hepatic intermediary metabolism of GIFT strain of Nile tilapia Oreochromis niloticus reared in freshwater

An 8‐week feeding experiment was conducted to determine the effect of dietary betaine levels on the growth performance and hepatic intermediary metabolism of genetically improved farmed tilapia (GIFT) strain of Nile tilapia Oreochromis niloticus (mean initial body weight: 78.3 ± 1.3 g, means ± SD). Six practical diets were formulated with the incorporation of betaine at the levels of 0 (control), 5, 10, 15, 20 and 25 g kg⁻¹. Survival showed no significant differences among the treatments (P > 0.05). The highest and lowest weight gain (WG) and specific growth rate (SGR) were observed for fish fed the diets containing 5 and 0 g kg⁻¹ (control) betaine, respectively. Feed intake showed similar trend with WG and SGR. In contrast, feed conversion ratio was the lowest when dietary betaine level was 5 g kg⁻¹. In general, dietary betaine supplementation showed no significant effect on hepatic composition of tilapia. Condition factor and viscerosomatic index tended to increase with increasing dietary betaine levels from 0 to 5 g kg⁻¹ and then decline when dietary betaine levels further increased from 5 to 25 g kg⁻¹. In contrast, hepatosomatic index declined with increasing dietary betaine levels (P < 0.05). Dietary betaine levels significantly influenced several hepatic enzymatic activities, including succinate dehydrogenase, lactate dehydrogenase, malic dehydrogenase, lipoprotein lipase and hepatic lipase, suggesting that dietary betaine addition had significant effects on nutrient metabolism in the liver. Based on the second‐order polynomial regression analysis of WG, 12.5 g kg⁻¹ of dietary betaine level seemed optimal for genetically improved farmed tilapia strain of O. niloticus.     

吉富罗非鱼对饲料中苯丙氨酸的需要量

分别用含6种水平(质量比分别为0.78%、0.95%、1.09%、1.34%、1.51%和1.72%)苯丙氨酸(phenylalanine,Phe)的等氮等能(粗蛋白30.10%,总能17.73 MJ/kg)饲料,在池塘网箱中(实验期间水温为24~32℃)饲喂初始体重为(52.70±1.80)g的吉富罗非鱼60 d,考察饲料Phe对吉富罗非鱼(GIFT,Oreochromis niloticus)生长性能、饲料系数、体成分、部分血清生化指标及前肠消化酶活性的影响,以期获得吉富罗非鱼对饲料苯丙氨酸的需要量。结果表明,随着饲料中Phe水平的升高,吉富罗非鱼的增重率、特定生长率、蛋白质效率、蛋白质沉积率、肥满度、肝体比和脏体比均呈现先上升后下降的趋势,饲料系数呈现先下降后上升的趋势;全鱼粗脂肪和全鱼灰分含量显著上升(P0.05),肌肉灰分含量显著下降(P0.05)。饲料中Phe对全鱼水分和粗蛋白质、肌肉水分、肌肉粗蛋白质和肌肉粗脂肪含量无显著性影响(P0.05);各实验组的肌肉氨基酸含量差异不显著(P0.05)。饲料中Phe显著影响血清中谷丙转氨酶活性,甘油三酯、总胆固醇和葡萄糖的含量(P0.05),对谷草转氨酶活性无显著性影响(P0.05);Phe显著影响肠蛋白酶、肠脂肪酶和肠Na~+-K~+-ATP酶活性(P0.05),而对肠淀粉酶活性影响不显著(P0.05)。以增重率、饲料系数和蛋白质效率为评价指标,通过二次回归分析可知,吉富罗非鱼对饲料中Phe需要量为1.17%~1.21%,占饲料蛋白质的3.89%~4.02%。本研究结果为合理配制吉富罗非鱼配合饲料提供了理论依据。     

Enhancing Growth of Common Carp, Rohu and Mozambique Tilapia through Plant Substrate: The Role of Bacterial Biofilm

Experiments were conducted to enhance the growth of common carp (Cyprinus carpio), rohu (Labeo rohita) and Mozambique tilapia (Oreochromis mossambicus) through use of sugarcane bagasse as substrate. Bagasse was suspended in water with or without supplementation with fertilizers. Bagasse supplemented with cattle dung and urea favoured higher zooplankton production and significantly (p < 0.05) increased fish growth by over 50% compared to bagasse or fertilizers on their own. This higher production of fish is attributed to bacterial biofilm promoted on the substrate which, apart from forming food for zooplankton and fish, contributed to improved water quality by lowering ammonia.     

尼罗罗非鱼无乳链球菌病的病理学研究

为了解尼罗罗非鱼感染无乳链球菌后各组织的病理变化,运用革兰氏染色和电镜负染技术对一株从自然发病的尼罗罗非鱼上分离的无乳链球菌进行形态观察,采用组织切片和超薄切片电镜技术对患病尼罗罗非鱼的肝脏、脾脏、肾脏、脑、心肌、骨骼肌、肠、鳃等8种组织进行病理学研究,探讨该病的致病机理。结果显示,革兰氏染色呈阳性,负染后透射电镜观察多数细菌呈链状排列;组织病理学变化主要是各内脏器官的广泛充血、水肿、变性和炎性细胞浸润,严重的细胞坏死;超微病理显示,大量球菌侵染脾脏等内脏组织,破坏细胞结构和各种细胞器;细胞界限模糊,细胞核畸形,线粒体肿大,嵴断裂,溶解;粗面内质网肿大、核糖体脱落;细胞质空泡化严重;心肌和骨骼肌纤维断裂、紊乱、肌节长短不一;肠微绒毛排列不整齐、长短不一;眼中有纤维性沉积。研究表明,无乳链球菌能造成尼罗罗非鱼全身性组织器官损害和炎症反应,尤其是肝脏、脾脏、肾脏和脑等重要器官功能障碍和衰竭,最后导致鱼体死亡。     

Comparative digestion efficiencies in conventional, genetically improved and genetically male Nile tilapia, Oreochromis niloticus (L.)

Apparent digestibility of dry matter, protein, lipid and energy of a fishmeal‐based feed (41% crude protein, 9% crude lipid and 19 kJ g⁻¹ gross energy) was compared in genetically improved farmed tilapia (GIFT), genetically male Nile tilapia (GMNT) and conventional Nile tilapia (CNT) (Oreochromis niloticus). The experimental fish were reared individually under standardized conditions in a recirculation system at 27±0.1°C for 10 weeks. Titanium dioxide (TiO₂) was used as a marker. Faeces of individual fish were collected daily by siphoning and stored at −18°C before analysis. No significant differences (P<0.05) were observed in the digestibility coefficients of feed dry matter (78.2±3.4%, 77.7±4.4% and 76.4±3.7%), protein (87.9±3.0%, 88.4±2.8% and 88.0±3.3%), lipid (90.0±2.5%, 91.0±2.1% and 89.4±3.0%) and energy (90.4±1.9%, 90.7±2.0% and 89.4±2.3%) in GIFT, GMNT and CNT respectively. At the end of the experiment, there were no significant differences (P<0.05) in average percentage growth (82.2±7.2, 87.3±7.7 and 74.7±4.1 respectively for GIFT, GMNT and CNT), growth rates or feed utilization efficiencies between the three tilapia groups. We conclude that the higher growth claimed for improved GIFT and GMNT as compared with CNT, if ever existing, cannot be attributed to higher nutrients or energy digestibility.