Developmental changes in structure and polypeptide profile of the androgenic gland of the freshwater prawn Macrobrachium rosenbergii

Although the mechanism of sex-differentiation in crustaceans has yet to be defined, the androgenic gland (AG) is thought to be the exclusive organ that produces the androgenic hormone (AH) which induces male sexual development. This paper presents results of light and transmission electron microscopy and total protein analysis of androgenic glands from three male morphotypes (orange-claw, orange-blue-claw and blue-claw) of the freshwater prawn, Macrobrachium rosenbergii. Highest protein content (76 µg//AG) was found in the blue-claw morphotype as compared to the orange-blue-claw (45 µg/AG) and the orange-claw morphotype (19 µg/AG). Sodiumdodecyl sulfate polyacrylamide gel electrophoresis (SDS-page) analysis of the cell free extract of the AG from the three morphotypes revealed four polypeptides (16, 18, 23 and 26 Kd) which quantitatively increase from the sexually immature orange-claw to the sexually mature blue-claw morphotype. The 16 and 18 Kd polypeptides could be the AHs.     

The effects of dietary lipid sources and lecithin on the production of giant freshwater prawn <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis> larvae in the Mekong Delta region of Vietnam

The giant freshwater prawn, Macrobrachium rosenbergii, is cultured widely in the Mekong Delta region of Vietnam but it is often difficult or expensive for hatchery operators to purchase commercial diets used as a feeding supplement to Artemia nauplii. Therefore, in the present study, the effects of lipid sources and lecithin on the growth and survival rate of M. rosenbergii larvae were examined in order to develop suitable hand-prepared larval diets for seed production of M. rosenbergii in this area. Six egg custard diets consisting of various ratios of lipid (originating from soybean oil and squid oil) and lecithin were used for rearing Macrobrachium rosenbergii larvae. Treatments in which larvae were fed diets containing squid oil exhibited the highest body length and survival rates (7.14–7.43 mm and 51.1–68.1%, respectively), and differed significantly from other treatments (P<0.05). Use of dietary soybean oil yielded the lowest body length and survival rates (6.29–6.75 mm and 22.0–48.7%), respectively). The supplementation of dietary lecithin did not increase final body weight but did improve larval survival rates. The n-3 HUFA content of prawns fed dietary squid oil was higher than those of animals provided with other diets. These results indicated that the most appropriate diet for rearing M. rosenbergii larvae is the diet containing 3% squid oil and 1.5% lecithin.     

大豆抗原蛋白对罗氏沼虾生理生化及免疫的影响

为探讨大豆抗原蛋白与豆粕饲用效果的关系,本研究配制4种等氮等能的实验饲料,以含有21.5%鱼粉、15.45%豆粕和15%发酵豆粕的实用饲料为基础饲料(T15组),用发酵豆粕完全替代T15组中的豆粕(TF组),比较发酵豆粕对豆粕的替代效果;再以鱼粉、酪蛋白和大豆分离蛋白为主要蛋白源分别配制与T15、TF组相近抗原蛋白含量的半纯化饲料AP5、AP0(抗原蛋白含量分别为5%和0%)组,探究抗原蛋白的生物学效应。选用初始体重为(0.17±0.02) g的罗氏沼虾(Macrobrachium rosenbergii)在室内水泥池网箱中进行为期64 d的养殖实验。结果显示:两种系列饲料中,大豆抗原蛋白含量的降低对罗氏沼虾生长、血清生化指标及免疫相关基因表达有不同的影响。在实用饲料组中,随着大豆抗原蛋白的降低,罗氏沼虾的增重率、肝胰腺蛋白酶活力、血清白蛋白、总蛋白、鳃Toll受体mRNA、NF-κB mRNA和肝胰腺HSP70 mRNA相对表达量都显著降低(P0.05),而血清超氧化物歧化酶活力显著升高(P0.05);在纯化饲料组中,随着大豆抗原蛋白的降低,罗氏沼虾的增重率、血清超氧化物歧化酶活力和丙二醛含量、肝胰腺HSP70mRNA相对表达量没有显著性差异(P0.05),肝胰腺淀粉酶活力、蛋白酶活力、血清白蛋白、总蛋白都显著降低(P0.05),而肌肉粗灰分、血清谷草转氨酶活力、鳃Toll受体mRNA、NF-κBmRNA相对表达量显著升高(P0.05)。比较实用饲料组与半纯化饲料组的结果可知,罗氏沼虾对实用饲料中5%的大豆抗原蛋白有一定的耐受性,并且有利于其生长和健康,推测大豆抗原蛋白与豆粕中的其他抗营养因子间存在有益的联合效应,显著降低其中的大豆抗原蛋白含量则不利于蛋白合成代谢和肝胰腺健康,导致生长性能下降。建议在实际生产中发酵豆粕和豆粕按一定比例混合使用。     

实时荧光定量PCR检测凡纳滨对虾和罗氏沼虾卵黄蛋白原mRNA在卵巢和肝胰腺中的表达

卵黄磷蛋白作为卵黄蛋白的主要成分, 可为甲壳动物胚胎和早期幼体发育提供能量, 为研究其来源及合成规律, 实验应用SYBR GreenⅠ荧光定量PCR法检测了凡纳滨对虾和罗氏沼虾性腺不同发育时期卵巢和肝胰腺两种组织中卵黄蛋白原mRNA的表达水平。结果发现,凡纳滨对虾和罗氏沼虾的卵巢和肝胰腺中都有卵黄蛋白原mRNA的表达。随着卵巢的发育, 凡纳滨对虾卵巢中卵黄蛋白原mRNA的相对表达量在前5个阶段不断增加, 分别为1.1, 5.9, 10.4, 26.9, 85.0, 恢复期急剧减少, 为1.6。肝胰腺中的相对表达量也不断增加, 分别为1.3, 3.3, 7.1, 37.3, 51.6, 恢复期急剧减少, 为1.0。罗氏沼虾肝胰腺中卵黄蛋白原mRNA的相对表达量在前四个阶段不断增加, 分别为3.4, 12.6, 15.2, 38.9, 抱卵期急剧减少, 为2.9;而卵巢在整个发育过程中对卵黄蛋白原合成的贡献比较小, 分别为1.0, 1.3, 1.7, 4.8, 1.5。研究表明, 两种虾类的肝胰腺和卵巢均具合成卵黄蛋白的功能, 而且在不同的卵巢发育阶段呈现明显的规律性。     

Growth and carcass composition of giant freshwater prawn, Macrobrachium rosenbergii (De Man), fed different isonitrogenous and isocaloric diets

A feeding experiment was conducted for 135 days to observe the effect of different isonitrogenous (35% crude protein) and isocaloric (385 kcal) diets on the growth and carcass composition of giant freshwater prawn, Macrobrachium rosenbergii ( De Man 1879 ). Three experimental diets (ED1, ED2 and ED3) were prepared using locally available ingredients. These diets differed mainly in terms of percent contribution of major protein sources such as fish meal, soybean meal, groundnut oil cake and mustard oil cake. Experimental diets were evaluated against a commercial diet, which served as the control (CD). Juveniles 1.87–2.44 g in size were stocked at a population density of 40 000 ha⁻¹ and fed thrice daily at 10% in the beginning and reducing gradually to 7% and 5% of the body weight during the experimental period. No significant differences (P>0.05) in the growth performance were observed; however, a significantly (P<0.05) higher yield (721.9 kg ha⁻¹ 135 days⁻¹) was recorded for prawn fed with control diet, followed by experimental diet 2 (676.5 kg ha⁻¹ 135 days⁻¹, having soybean meal as a major protein source). The survival ranged between 63.8% and 77.7%, with different diets showing significantly higher survival. The apparent feed conversion ratio values of diets ranged between 3.15 and 3.49, with experimental and control diets showing non‐significantly lower AFCR values. At the end of the experiment, representative specimens from each treatment were collected and their carcass composition was measured. Analysis of variance showed that carcass protein and total carbohydrate contents were significantly (P<0.05) higher in prawns fed on a fish–soybean meal‐based diet (ED3) and a control diet. The total lipid contents of prawns, however, did not differ significantly among the various dietary treatments. The results of our study suggest that the experimental diets could be used effectively for M. rosenbergii without compromising growth and flesh quality.     

Hatchery seed production of giant freshwater prawn,Macrobrachium rosenbergii using inland ground saline water in India

The suitability of inland saline water (ISW) from the Lahli‐Baniyani Fish Farm, Rohtak was investigated for the larval rearing of giant freshwater prawn (GFP), Macrobrachium rosenbergii. Six experiments were conducted. In Experiment‐I, 54% of the larvae metamorphosed to postlarvae (PL) in constituted seawater (CSW) whereas total mortality occurred at larval stages (LS)‐II and LS‐III in ISW with salinity of 12 g L^?1. Larvae survived to LS‐IV in Experiment‐II, when ISW was supplemented with K⁺~ SW. In Experiment‐III, total hardness in ISW was reduced serially, but K⁺ ~ SW was supplemented. The larvae did not survive beyond LS‐V. In Experiment‐IV, ISW was amended with different ratios of Mg²⁺/Ca²⁺ and K⁺ ~ SW. The larvae successfully metamorphosed to postlarvae with highest survival of 51.6% in Mg²⁺/Ca²⁺ ratio of 2.5. In Experiment‐V, eight larval cycles were run with water quality used in Experiment V, where all the cycles produced PL's with a survival rate of 20–67%. In Experiment VI, the larvae were reared in Mg²⁺/Ca²⁺ ratio of 2.5 and different levels of K⁺ to optimize its requirement. The ISW amended with K⁺ 80% ~ SW and Mg²⁺/Ca²⁺ ratio of 2.5 was found to be commercially suitable for the seed production of GFP.     

Comparison of larval performance between Thai and Vietnamese freshwater giant prawn, Macrobrachium rosenbergii (de Man): a preliminary study

This study compared the performance of larvae of giant freshwater prawn (Macrobrachium rosenbergii) from Thailand and Vietnam. Thai broods were collected from a farm and Vietnamese broods were collected from a river. Larvae from these two sources were raised in identical environments, and their rates of development and survival as well as their ability to withstand environmental stresses were assessed. The first postlarval stage was observed in both strains on day 22. All larvae (100%) from Thai broods completed metamorphosis by day 36, but only 89% of the Vietnam strain completed metamorphosis by day 45. The stages of development were more uniform in larvae from the Thai stock than the Vietnamese stock. Survival differences were observed within the first week (92% in the Thai group vs. 55% in the Vietnamese group). These differences were most pronounced beginning in week 5 (52% and 16% respectively) and week 7 (33% and 2% respectively). No clear difference was found in brood size and fecundity between the two groups. No difference in survival was observed between the two groups of larvae challenged with salinity, oxygen or formalin. Differential development rates of larvae in the same batch would naturally create conditions favourable for cannibalism and impaired ability to capture food. The earlier and more uniform rate of development, and subsequent higher rate of survival of Thai stock compared with the Vietnamese wild stock is suggested to be due to inadvertent selection in the domesticated stock.     

The Effect of Biomass Density,Temperature, and Substrate on Transport Survival of Market-Size Freshwater Prawn,Macrobrachium rosenbergii

Abstract

After harvest, adult prawn are often transported for sales to live markets, such as ethnic Asian outlets, in major urban centers. Poor survival during transportation has hindered development and expansion of these markets. Methodologies to increase survival during transport could contribute to industry viability. Three independent trials were conducted. In the first trial, three biomass densities (25, 50 and 100 g/L) were evaluated in 100-L, open plastic containers aerated with pure oxygen and compressed air. Water quality analyses were performed prior to stocking. After 24 hours in the model transport containers, water quality analysis was conducted and all prawn were removed, determined to be alive or dead, and each group weighed and counted. There was no significant difference (P > 0.05) for prawn survival (overall mean 98%) among the three densities. Concentrations of dissolved oxygen and nitrite were not effected by hauling density (P < 0.05). Total ammonia-nitrogen and un-ionized ammonia-nitrogen concentrations increased (P < 0.05) as biomass densities increased, though values remained within what are considered tolerable ranges. In the second trial, the effect of added substrate and temperature on transport survival was evaluated with prawns stocked at the high density (100 g/L). Two water temperatures (21°C and 26°C) with and without substrate were evaluated in a 2 × 2 factorial with three replicate, 100-L model transport containers per treatment combination (12 containers total). Factorial analysis indicated no significant statistical interaction (P > 0.05) between the presence of substrate and water temperature on any measured variable. The main effects of substrate and temperature were then analyzed separately. The presence or absence of substrate had no significant impact (P > 0.05) on prawn survival. However, temperature had a highly significantly impact (P < 0.01) on survival; prawn survival at 21°C averaged 97% compared to 24% at 26°C. The third trial was a commercial verification trial in which 500 kg of live prawn were transported to New York from Kentucky. These data indicate prawn can be successfully transported at 100 g/L for 24 hours when temperatures are maintained near 21°C. Adding substrate to the transport tank appears to provide no benefit.     

Osmoregulation,growth and moulting cycles of the giant freshwater prawn (Macrobrachium rosenbergii) at different salinities

The giant freshwater prawn, Macrobrachium rosenbergii, is a species with a high commercial value in aquaculture. Two experiments were performed to determine the effects of salinities on the osmoregulation, growth and molting cycles of M. rosenbergii during growout. The first experiment was designed to determine whether these animals are capable of adapting to the changes in salinity seen in salinity intrusions in tropical deltas, with an incremental increase in salinity of 3‰ per day from 0‰ to 30‰ Haemolymph osmolality was rapidly regulated up to salinities of 15‰ , whereas animals conformed at higher salinities. The second experiment determined the growth, moulting cycle, osmolality, muscle water content and mortality during a 4‐month experiment at 0‰, 15‰ or 25‰ salinity. The weight gains in 0‰ and 15‰ were not significantly different and were comparable to the growth rates achieved in production farms with body mass increases of 2.6 and 2.3‐fold their initial body mass, respectively, after 4 months. The 25‰ group suffered from low growth, high mortality and a significantly lower moulting frequency. These data show that this species can be reared in brackish water up to 15‰, allowing for farming in the large areas impacted by salt water intrusions in tropical deltas.     

Evaluation of a spray-dried artificial diet for larval culture of freshwater prawn, Macrobrachium rosenbergii, and striped bass, Morone saxatilis

Larvae of the freshwater prawn, Macrobrachium rosenbergii (De Man), and the striped bass, Morone saxatilis (Walbaum), were fed artificial diets manufactured by a spray-drying process or live Artemia nauplii , separately or in various combinations. Spray-dried diets were neutrally buoyant, water stable (low protein leaching rate), and were satisfactorily consumed as verified by the observation of full guts after feeding. Survival and growth of larvae fed live Artemia nauplii was significantly greater than those of larvae fed spray-dried diets. Lowest survival and growth rates were observed when larvae were fed artificial diets exclusively from the onset of exogenous feeding. Survival rates were positively related to the duration of feeding live Artemia nauplii before weaning to artificial diets. The poor performance associated with spray-dried artificial diets may be the result of the digestive capabilities of the larvae of caridean shrimp and striped bass being insufficient to process compact, dense particles.     

Liver oil of pharaoh cuttlefish Sepia pharaonis Ehrenberg, 1831 as a lipid source in the feed of giant freshwater prawn, Macrobrachium rosenbergii (De Man 1879)

The efficacy of pharaoh cuttlefish ( Sepia pharaonis Ehrenberg, 1831) liver lipid in the feed for juveniles of giant freshwater prawn Macrobrachium rosenbergii (De Man 1879) was tested by feeding five experimental diets prepared using clam meat, groundnut oil cake, wheat bran, tapioca powder, vitamin–mineral mixture and cellulose powder as the major ingredients. The test diets T₁, T₂, T₃, T₄ and T₅, containing five levels (1, 2, 3, 4 and 5%, respectively) of lipid, extracted from the liver of pharaoh cuttlefish, were fed to 30-day-old prawn juveniles for 60 days, in triplicates and compared against a control. Analysis of variance of the growth parameters showed that the juveniles fed with T₂, containing 2% cuttlefish liver lipid with a total lipid content of 9.85% and lipid–carbohydrate ratio of 1 : 3.8, showed significantly better growth ( P  < 0.05) with the highest weight gain of 118%, greatest food conversion and protein utilization efficiency, and the highest body protein content, although the survival rates remained unaffected among treatments. Growth of the juveniles, however, declined at lipid levels >2%. Addition of cuttlefish liver lipid led to an increase of ω-3 and ω-6 fatty acids in T₂, the proportion of ω-6 being higher than the former. The crude lipid content of the body of test animals also increased with the increase in dietary lipid from 1.51% in T₁ to 3.27% in T₅. The present study indicates that cuttlefish liver lipid can be successfully used as a substitute for conventional lipid sources in rearing juveniles of giant freshwater prawn, an eco-friendly practice in recycling cuttlefish waste – a discarded fishery by-product.     

Genetic diversity of cultured and wild populations of the giant freshwater prawn Macrobrachium rosenbergii (de Man, 1879) based on microsatellite analysis

Freshwater prawn (Macrobrachium rosenbergii) culture in the Western Hemisphere is primarily, if not entirely, derived from 36 individual prawns originally introduced to Hawaii from Malaysia in 1965 and 1966. Little information is available regarding genetic variation within and among cultured prawn stocks worldwide. The goal of the current study was to characterize genetic diversity in various prawn populations with emphasis on those cultured in North America. Five microsatellite loci were screened to estimate genetic diversity in two wild (Myanmar and India‐wild) and seven cultured (Hawaii‐1, Hawaii‐2, India‐cultured, Israel, Kentucky, Mississippi and Texas) populations. Average allelic richness ranged from 3.96 (Israel) to 20.45 (Myanmar). Average expected heterozygosity ranged from 0.580 (Israel) to 0.935 (Myanmar). Many of the cultured populations exhibited reduced genetic diversity when compared with the Myanmar and the India‐cultured populations. Significant deficiency in heterozygotes was detected in the India‐cultured, Mississippi and Kentucky populations (overall F_is estimated of 0.053, 0.067 and 0.108 respectively) reflecting moderate levels of inbreeding. Overall estimate of fixation index (F_st = 0.1569) revealed moderately high levels of differentiation among the populations. Outcome of this study provide a baseline assessment of genetic diversity in some available strains that will be useful for the development of breeding programmes.     

不同脂肪源对罗氏沼虾生长及体组织常见组分的影响

用5种不同脂肪源组合的饲料(Ⅰ.鱼油0.5%+豆油2.5%;Ⅱ.鱼油0.5%+菜籽油2.5%;Ⅲ.鱼油0.5%+花生油2.5%;Ⅳ.鱼油0.5%+亚麻油2.5%;Ⅴ.豆油1.5%+亚麻油1.5%)投喂体重为(2.22±0.04)g的罗氏沼虾(Macrobrachium rosenbergii)40 d,研究不同脂肪源对其生长及全虾和肌肉中水分、粗蛋白、粗脂肪含量的影响。结果显示:在生长方面,第Ⅴ组的罗氏沼虾增重显著高于Ⅱ组和Ⅲ组(P<0.05),Ⅰ组和Ⅳ组增重也显著大于Ⅱ组(P<0.05)。在体成分方面,Ⅰ组全虾总水分含量最低,显著低于Ⅲ组和Ⅳ组(P<0.05),其他各组间无显著差异(P>0.05);Ⅴ组全虾粗脂肪含量最高,显著高于其他各试验组(P<0.05);Ⅲ组全虾粗蛋白含量显著低于Ⅰ组、Ⅱ组及Ⅴ组(P<0.05);Ⅳ组肌肉总水分含量显著高于其他各组;肌肉粗脂肪和粗蛋白含量各试验组之间差异不显著(P>0.05)。     

罗氏沼虾养殖群体表型性状间的相关性及类群差异分析

为研究罗氏沼虾(Macrobrachium rosenbergii)养殖群体表型性状间的相互关系及不同类群间的性状差异,本研究对人工养殖的罗氏沼虾雌、雄及“老头虾”3个类群共490个个体的体重、体长、全长等12个表型性状进行了相关分析、形态性状对体重影响的通径分析等。结果表明, 3个类群除上、下额刺数2个可数性状外,其他9个可量形态性状与体重都呈极显著的正相关(P<0.01);影响体重的关键形态性状在3个类群中各不相同,但体长、头胸甲长、第二步足长在3个类群中均是影响体重的关键指标;分别建立了各类群体重与关键形态性状的多元回归方程。聚类分析和主成分分析结果表明,雌、雄2个类群表型上更为相似,“老头虾”与雌性个体的差异最大。腹部轮廓特征(包括腹长、腹宽、腹高)、全长、体长及第二步足长对3个类群的差异贡献较大。雌性个体腹部发达,“老头虾”则第二步足尤为发达。本研究结果可为罗氏沼虾的选择育种、基础生物学及行业标准的制定提供数据资料。     

罗氏沼虾开放和闭锁核心育种群生长和存活性能分析

开放核心育种体系可增加核心群体的选择强度,进而增加育种目标性状的遗传进展。本研究以罗氏沼虾(Macrobrachium rosenbergii)为研究对象,向闭锁核心群(closed nucleus population,NP)内引入扩繁群(multiplier population, MP)个体,构建两个杂交群体(正交群体NP/MP,反交群体MP/NP),并以闭锁核心群(NP/NP)为对照,应用线性混合效应模型(linear mixed effects model, LME)和广义线性混合模型(generalized linear mixed model, GLMM)对不同群体收获体重和存活率的估计边际均值进行比较,评估在虾类选择育种中构建开放核心育种体系的可行性。结果显示:(1) NP/NP、MP/NP和NP/MP群体的收获体重估计边际均值分别为45.83 g、49.57 g和46.62 g;与NP/NP群体相比, MP/NP和NP/MP群体分别提高了8.16%和1.72%。(2) NP/NP、MP/NP和NP/MP群体的存活率估计边际均值分别为72.92%、68.04%和66.55%;与NP/NP群体相比,MP/NP和NP/MP群体分别降低了6.69%和8.74%。综上所述,在罗氏沼虾核心群中引入扩繁群个体,构建开放核心育种群体,可以有效地增加收获体重的遗传进展;同时在制定选择指数时,应加大存活性状的权重,选择生长和存活性能均优良的家系生产扩繁群体,导入闭锁核心育种群,构建生长和存活性能均优良的开放核心育种群。     

饲料低蛋白、高脂肪和高消化能对斑点叉尾鮰

为了探讨高脂肪条件下不同的蛋白和能量水平对斑点叉尾鮰生长及体组成的影响,试验设2个蛋白水平(22%,28%),2个脂肪水平(10.0%,14.0%),2个消化能水平(12.56 kJ/g,14.23 kJ/g),共8组,分别为P28L10E14.23,P28L14E14.23,P22L10E14.23,P22L14E14.23,P28L10E12.56,P28L14E12.56,P22L10E12.56和P22L14E12.56。试验饲料配方使用鱼粉和豆粕调节蛋白含量,混合油脂(鱼油∶玉米油=1∶1)调节脂肪含量,α-淀粉、次粉和麸皮调节消化能含量,并以微晶纤维素为填充物,每组3个重复,每个重复20尾鱼(141.5?1.0) g。饲养60 d后,进行生产性能测定,并采集组织样本,测定相关指标。结果表明,鱼体末重(FW)、增重率(WG)、特定生长率(SGR)和饵料系数(FCR)不受饲料蛋白、脂肪和消化能单一营养水平影响(P>0.05);但与饲料蛋白、脂肪和消化能三者的交互作用(P<0.01)有关。胴体蛋白、脂肪含量与饲料脂肪和消化能水平相关(P<0.05)。由此可见,饲料过高脂肪和消化能对斑点叉尾鮰没有额外的促生长作用;饲料蛋白水平达到22%时,即可满足140~300 g斑点叉尾鮰的营养需要;饲料中22%的蛋白、10%的脂肪、12.56 kJ/g的消化能即可满足斑点叉尾鮰仔鱼的生长需要,同时又能保证其正常生理机能,建议可在实际生产配方中作参考值。     

Effects of feeding (ω-3) HUFA-enriched Artemia during a progressively increasing period on the larviculture of freshwater prawns

Larvae of the freshwater prawn (Macrobrachium rosenbergii) were reared to post-larvae in a closed recirculation system. Six treatments were designed where freshly-hatched Artemia nauplii were first given to the larvae for 3, 7, 11, 15, 17 and 25 days according to the treatment. After that (-3) HUFA-enriched Artemia were given until the 28th day at which time the test was terminated and evaluated. The requirement for (-3) Highly Unsaturated Fatty Acids (HUFA) for the larval stages of M. rosenbergii was confirmed by this experiment. Moreover, the longer the period of feeding on (-3) HUFA-enriched Artemia nauplii, the better the results in terms of growth, metamorphosis rate, survival and stress resistance.     

Experimental susceptibility of different life-stages of the giant freshwater prawn, Macrobrachium rosenbergii (de Man), to white spot syndrome virus (WSSV)

Studies were conducted by injecting/feeding white spot syndrome virus (WSSV) derived from infected shrimp, Penaeus monodon (Fabricius), to different life-stages, namely post-larvae, juveniles, sub-adults and adults of Macrobrachium rosenbergii (de Man). The disease was also induced in brood stock, and the eggs and larvae derived from these animals were subsequently tested for WSSV infection. All the stages except egg used for the experiment were found WSSV positive in histopathology, cross infection bioassay and polymerase chain reaction (PCR) analysis. Experimentally infected post-larvae and juveniles showed a high percentage of mortality and an increased rate of cannibalism. The cumulative mortality in post-larvae was up to 28%; with 28–40% cannibalism resulting in a maximum loss of up to 68%. In juveniles, observed mortality and cannibalism were 10–20% and 6.7–30.0%, respectively, and the maximum loss recorded was 50%. In sub-adults, mortality ranged from 2.8 to 6.7%, cannibalism was up to 20% and the total loss was up to 26.7%. Sub-adults and adults were found to be more tolerant to the infection as evidenced by the mortality pattern. A nested (two-step) PCR resulted in a 570-bp product specific to WSSV in all stages, except the eggs.     

Evaluation of vitamin C-enriched Artemia nauplii for larvae of the giant freshwater prawn

The effect of high levels of ascorbic acid (AA) delivered through enriched live food has been verified through the successful culture of larval giant freshwater prawn, Macrobrachium rosenbergii. Two successive feeding trials were set up using a control (550 g AA g^–1 DW) and two different AA-enrichment levels in Artemia (1300 and 2750 g AA g^–1 DW). Under standard culture conditions, no differences in growth nor survival could be observed demonstrating that the nutritional requirements are below 550 g AA g^–1 DW, which is the normal level occurring in freshly-hatched Artemia. However, a significantly positive effect could be demonstrated on the physiological condition of the postlarvae, measured by means of a salinity stress test, when vitamin C-boosted live food was administered. Since the AA levels in the predator larvae are linked with the enrichment levels in the live prey, it may be assumed that a positive influence on stress resistance was caused by feeding vitamin C-enriched Artemia. It is expected that under suboptimal conditions, supplementation of high vitamin C levels might also enhance production characteristics.