Relation between lipid and fatty acid composition of eggs and larval survival in white pacific shrimp (Penaeus vannamei, Boone, 1931)

In this study, lipid classes and fatty acid composition were determinedin eggs of P. vannamei as a function of survival to zoeaIII stage. Spawns were reared individually to zoea III and grouped, accordingtotheir final survival to this larval stage, into spawns of high and lowsurvival.Eggs of individual spawns were analyzed for lipid and fatty acid composition ofneutral and polar lipids and the results were then grouped according tosurvivalto zoea III. The lipids within each group (high and low survival to zoea III)were pooled for the separation of phospholipids and the analysis of their fattyacid composition.Higher levels of triglycerides, carotenoids, and linoleic (18:2n-6) acid ineggs were associated with improved survival to zoea III. Linoleic acid washigher in spawns from the high survival group in both neutral and polarfractions and in most of the phospholipid classes analyzed. Docosahexanoic acid(DHA) was not related to survival to zoea, probably because its content washighenough (> 15% of total fatty acids) to satisfy embryo and early larvaldevelopment needs. A high content of eicosapentaenoic acid (EPA) was found inphosphatidylethanolamine, lysophosphatidylethanolamine, phosphatidylserine, andphosphatidylinositol compared to other phospholipid classes, suggesting aspecific role of EPA in these lipids. These results describe the specificphospholipid composition of penaeid eggs and could (potentially) be used aspredictive indicators of larval quality for research and production purposes.     

Genetic differentiation in hatchery strains and wild white shrimp Penaeus (Litopenaeus) vannamei (Boone, 1931) from northwest Mexico

Ten enzymatic systems were analyzed to determine allozyme genetic differentiation among three hatchery strains (A, B and C) of white shrimp, Penaeus (Litopenaeus) vannamei, commonly used in shrimp farming in northwest Mexico. A wild population from northern Sinaloa was used as a reference. Fifteen loci were detected, nine of which were polymorphic (ACP-1*, ACP-2*, AKP-2*, EST-2*, EST-3*, EST-4*, EST-5*, LAP*, and LDH*). Polymorphism of A, B and C were 53, 53, and 40%. The mean observed heterozygosity per locus was 0.071, 0.093, and 0.050 without any significant difference among them or with respect to the wild population (0.056). In all samples observed heteroxygosity was smaller than expected. The mean number of alleles per locus was 1.8 in A and 1.87 in both B and C. Strain A was the only sample without rare alleles. Only EST-3* and LAP* of strain A were in Hardy-Weinberg equilibrium; the other loci were in disequilibrium in all samples. High inbreeding values and heterozygote deficiencies were detected in all samples. Distribution of allelic frequencies was heterogeneous among the samples (G-test), involving all polymorphic loci and suggesting a genetic differentiation. According to Fst, a moderate genetic differentiation (7.4%) was detected among the samples. Greater differences were between strains A and C. Based on genetic distance, the samples were grouped into two pairs, B–C and A-wild. Strain A is a young strain related to the wild sample, whereas strains B and C have a different geographic origin than the wild sample.     

Genetics of the resistance to hypoxia in postlarvae and juveniles of the Pacific white shrimp Penaeus (Litopenaeus) vannamei (Boone 1931)

The genetics of resistance to hypoxia was studied in shrimp using two approaches, heritability estimation and heterosis estimation. The heritability of resistance to hypoxia was evaluated in two populations of shrimp postlarvae families produced at different times, and heterosis was estimated through the reciprocal crosses of two genetically distinct shrimp populations at postlarvae and juvenile. Heritabilities of resistance to hypoxia in postlarvae were large and out of the range for the heritability (1.73±0.09, 1.35±0.14) regardless of population evaluated. When covariates (survival and mean total weight to postlarvae 15 days old) were introduced in the analyses to correct for effects during rearing of the larvae, the heritabilities did not change substantially for the first population, but were decreased for the second population depending on the covariate used for correction (1.15±0.10 and 1.08±0.11 for the covariates survival and total weight respectively). Those large heritabilities could be explained by the presence of confounded common environmental variance in the estimated genetic variance (maternal effects), or by dominance and epistatic effects being an important part of the estimated genetic variance. Heterosis analyses dissecting maternal effect indicated that both effects, maternal and dominance, are involved in the resistance to hypoxia at postlarvae, and that although maternal effects decreased at juvenile stage, the trait was still characterized by presenting a large heterosis value (62–65% for postlarvae and 36% for juveniles).     

Quantitative genetic parameter estimates for size and growth rate traits in Pacific white shrimp, Penaeus vannamei (Boone 1931) when reared indoors

Heritabilities of size traits and growth rate traits, as well as genetic, phenotypic and environmental correlations were estimated at three ages for a captive population of Pacific white shrimp (Penaeus vannamei) grown indoors. A covariate, mean size or mean growth rate during early growth in individual tanks before tagging and mixing, was introduced in the analyses to reduce the error caused by unique previous growth conditions on variance components. Heritabilities of size traits increased with age, with the h² for TL, AL, TWt and Wi1AS being 0.15, 0.20, 0.20 and 0.22, respectively, at 17 weeks, increasing to 0.28, 0.33, 0.34 and 0.35 at 29 weeks of age. Heritabilities of growth rate traits estimated between consecutive growth periods decreased from the first (h² for ΔTL 0.65, ΔAL 0.71, ΔTWt 0.63 and ΔWi1AS 0.84) to the second period (h² for ΔTL 0.34, ΔAL 0.50, ΔTWt 0.54 and ΔWi1AS 0.52). Phenotypic correlations were always larger than genetic correlations for both, size and growth rate traits. Genetic correlations between size traits within age were high (r_G >0.95), but those between the same size trait at different ages decreased as the age difference increased in spite of a consistently high environmental correlation (r_E 0.80–0.85) between the same trait at different ages. Phenotypic and genetic correlation's between the same growth rate trait at the two different growth periods evaluated were negative or zero (r_G TL –0.26, AL –0.24, Wi1AS 0.00) with the exception of total weight (r_G TW 0.35) and the environmental correlations between growth periods were also low (r_E 0.13–0.32).     

Effect of hypo- and hyper-saline conditions on osmolarity and fatty acid composition of juvenile shrimp Litopenaeus vannamei (Boone, 1931) fed low- and high-HUFA diets

Litopenaeus vannamei (Boone) grown in ponds are exposed to salinities of less than 5 g L^?1 during inland shrimp culture or to more than 40 g L^?1 from evaporation and reduced water exchange in dry, hot climates. However, dietary requirements for shrimp grown in low or high salinities are not well defined, particularly for fatty acids. Feeding shrimp postlarvae with highly unsaturated fatty acids (HUFA) enhances tolerance to acute exposure to low salinity, as a result of better nutritional status, or/and specific effects of HUFA on membrane function and osmoregulation mechanisms. This study analysed the effect of HUFA supplementation (3% vs. 34%) on L. vannamei juveniles reared for 21 days at low (5 g L^?1), medium (30 g L^?1) and high salinities (50 g L^?1). Juveniles grown at 5 g L^?1 had lower survival compared with controls (30 g L^?1) or shrimp grown at 50 g L^?1, but no significant effect on survival was observed as a result of HUFA enrichment. In contrast, growth was significantly lower for shrimp grown at 50 g L^?1, but this effect was compensated by the HUFA‐enriched diet. Osmotic pressure in haemolymph was affected by salinity, but not by HUFA enrichment. Shrimp fed HUFA‐enriched diets had significantly higher levels of eicosapentaenoic acid and docosahexaenoic acid in hepatopancreas and gills. These results demonstrate that growth at high salinities is enhanced with diets containing high HUFA levels, but that HUFA‐enriched diets have no effect on shrimp reared at low salinities.     

南美白对虾细菌性白斑病与病毒性白斑的区别及防治对策

南美白对虾在养殖过程中如果受到细菌和病毒的侵袭,头胸甲壳上有点状或鱼鳞状白斑。一些养殖户对白斑病十分害怕,认为一旦对虾患上白斑病,就无法治愈了,其实,很多白斑病是可以治愈的。现将南美白对虾细菌性白斑和病毒性白斑的症状、预防措施和治疗方法做一介绍。     

Genetic variation of white spot syndrome virus (WSSV) in Pacific white shrimp Litopenaeus vannamei (Boone 1931) culture of Thailand

White spot syndrome virus (WSSV) is highly pathogenic to penaeid shrimp and has caused significant economic losses in the shrimp farming industry in Thailand. Genotyping analysis was done in 124 WSSV isolates from cultured Pacific white shrimp Litopenaeus vannamei. These samples were obtained during 2007–2014 from eight provinces in Thailand. We investigated five variable loci in the virus genome: deletions in two variable regions, VR14/15 and VR23/24, and three variable number tandem repeats (VNTR) located in open reading frame (ORF) 75, 125 and 94. WSSV genotype was characterized as (X_14/15, X_23/24) (N₇₅‐N₁₂₅‐N₉₄) where X is the number of base pair deletion in the variable region and N is the number of repeat units (RUs) in a specific ORF. The deletion pattern in VR14/15 and VR23/24 regions characterized three WSSV genotypes. The most prevalent genotype was (5950_14/15, 10971_23/24), and it was found in all studied areas. At least 33 genotypes of WSSV were analysed based on 3 VNTR loci, indicating that the VNTRs of WSSV genome are highly variable. From 124 WSSV samples, two samples presented the characteristic of all five variable loci similar to WSSV collected during 2010 in Saudi Arabia (5950_14/15, 10971_23/24) (3₇₅‐6₁₂₅‐7₉₄). Many different WSSV genotypes shown in this study as compared to previously reported genotypes in Thailand suggests current status of disease epidemiology, as well as probable movements of WSSV between countries.     

Selectivity of particle size by the shrimp Litopenaeus vannamei (Boone, 1931) larvae

Because of the filter‐feeding behavior of shrimp larvae, it is important to define precisely the size of the particle ingested in the different stages until postlarval stage where raptorial habits are more evident than the filter‐feeding lifestyle. Selectivity assays were conducted by using Polystyrene DVB particles with diameter between 1 and 50 μm as food. A group of organisms from each stage were put into the particle suspension for 15 min to let the polystyrene particles be ingested. The particle distribution in the media and the content of the gut of the larvae were characterized with digital image processing analysis. The results were compared using Ivlev selectivity formula, which compares the frequency distribution of each size of the particle in the media and in the gut of larvae. The results of selectivity were adjusted with a third‐order polynomial regression to determine the optimum and preferred size of the food particles for each larval stage between Zoea I and Postlarva I. It is concluded that the different larval stages of Litopenaeus vannamei may be considered as a single group of larvae who ingest foods with size between 5.71 and 20.33 μm. The optimal size of the food ingested was 14.42 μm wide.     

An evaluation of intraspecific competition for Pacific white shrimp Penaeus vannamei (Boone) in extensive/semi-intensive ponds

The hypothesis that intraspecific competition affects survival and growth during the culture and harvest at extensive/semi-intensive Penaeus vannamei shrimp ponds was evaluated. Thus, the effect of stocking density on the biomass, shrimp average weight, survival, and economic performance during the culture (133 days) and at the harvest of the P. vannamei shrimp was investigated in 400 m² earthen ponds. In order to reduce the likelihood of infectious diseases, shrimp received preventive health treatments (probiotics and β-1,3/1,6-glucans) during all culture phases. In this way, the effect of density on the intraspecific competition for space/food was isolated. Ponds stocked at 6, 9, and 12 shrimp m^?2 showed competition-dependent growth. Ponds stocked at 12 shrimp m^?2 presented a mortality (12 %) between days 76 and 99. Competition, and accordingly individual growth reduction, could have begun at day 76 at a density of 5 shrimp m^?2. Survival was significantly higher at 6 shrimp m^?2 (84.2 ± 6.2 %) compared with the 12 shrimp m^?2 (64.8 ± 12.4 %) treatment, while no significant differences in yield were observed between both treatments. Ponds stocked at 3 and 6 shrimp m^?2 presented the best benefit–cost rates. The optimal shrimp density during the experimental culture was 5 shrimp m^?2. Given the experimental conditions and considering the fraction of density-independent mortality observed, the optimum stocking density was found to be 6 shrimp m^?2.     

Antioxidant effects of nanoencapsulated lipoic acid in tissues and on the immune condition in haemolymph of Pacific white shrimp Litopenaeus vannamei (Boone, 1931)

The antioxidant and oxidative damage responses and immune parameters in shrimp, Litopenaeus vannamei, reared in clear water (CW) and in a biofloc system (BFT) were evaluated. The animals were given feed supplemented with either nanocapsules containing the antioxidant lipoic acid (NCLA) or empty nanocapsules (NC). Antioxidant and oxidative stress analyses were evaluated by measuring glutathione S‐transferase activity (GST), reduced glutathione (GSH) concentration and lipid peroxidation (TBARS) in the gills, hepatopancreas and muscle. The immune parameters were then determined by the differential hemocyte count in the haemolymph. The final weight of the shrimp reared in both CW and BFT and treated with NCLA increased (p < .05). The shrimps reared in BFT showed increased GST activity in the gills and hepatopancreas after NCLA treatment (p < .05). Higher GSH levels were observed in the hepatopancreas with NCLA supplementation in CW and BFT (p < .05). Decreased levels of TBARS were observed in the gills and muscles of shrimp supplemented with NCLA and maintained in CW (p < .05). A decrease in the percentage of hyaline hemocytes and an increase in granular hemocytes were observed in shrimp treated with NCLA in CW and BFT (p < .05). The antioxidant treatment induced positive responses in terms of the zootechnical, biochemical and immunological parameters.     

山区淡水池塘养殖南美白对虾试验

南美白对虾 (PenaeusvannameiBoone) ,又称凡纳对虾 ,原产于南美太平洋沿岸水域 ,是当今世界上公认最有前途的三大养殖虾类之一。它具有生长速度快、适应性强、盐度适应范围广、繁殖周期长、低盐度淡化养殖中病害少等优点 ,是山区池塘调整养殖结构、优化养殖品种、提高养殖效益的优良品种。为进一步探索南美白对虾在闽西地区稳产高效养殖技术 ,笔者于 2 0 0 3年 7月进行了南美白对虾池塘养殖试验 ,取得了一定经济效益和经验。现将试验情况总结如下。1　材料和方法1 .1　池塘条件　池塘选择在临城镇西郊村 ,面积0 .2 2hm2 ,池塘平均深度 2 .…     

Maternal and cage effects on genetic parameter estimation for Pacific white shrimp Penaeus vannamei Boone

Three sets of full-sib families of Pacific white shrimp Penaeus vannamei Boone, produced from females in different reproductive condition (15, 45 and 75 days after ablation and start of production), were used to estimate heritabilities and genetic correlations of growth traits for several larval and grow-out stages of development. Heritabilities for early larval length (nauplii) were larger when estimated from families produced 45 and 75 days after ablation than when estimated from families produced 15 days after ablation, indicating a maternal effect caused by lower reproductive quality of the females used to produce the second and third sets. However, the better reproductive quality of females used to produce the first set resulted in significant density effects on larval length, presumably caused by different mortalities occurring among families during larval culture, which also resulted in an increase in the heritability values estimated for late post-larvae stages. After transfer to grow-out cages in a pond, all estimated heritabilities decreased initially, then increased again. The increase in heritabilities was associated with a negative correlation between growth and density in the cages at 58 days. Lowering densities at this age resulted in a decrease in heritability values at 97 days, but an increase again thereafter. The largest genetic correlation with abdominal weight, the trait of most interest for improvement in shrimp, was total weight. That was followed by cephalothorax weight, width of first abdominal segment, abdominal length and total length. Among these, the trait with a consistently large heritability at 58 and 97 days, and with a large genetic correlation with abdominal weight, was width of first abdominal segment. This trait might provide a secondary or indirect trait to improve abdominal weight when combined with total weight for a selection programme.     

Cage culture of the Pacific white shrimp Litopenaeus vannamei (Boone, 1931) at different stocking densities in a shallow eutrophic lake

Postlarvae of Litopenaeus vannamei were acclimated and stocked in lake-based cages at the following stocking densities: 10, 20, 30 and 40 shrimp m⁻². Another set of shrimp was stocked in concrete tanks as reference samples at 30 shrimp m⁻². Significant differences were observed among stocking densities throughout the 95-day culture. The final weight at harvest decreased with increasing stocking density: mean weights of 23.3, 15.8, 13.0, 10.9 and 14.6 g for the 10, 20, 30, 40 shrimp m⁻² and reference tanks were observed respectively. There were no significant differences in survival throughout the culture period, ranging between 69% and 77%. Daily growth rates (range: 0.11–0.24 g day⁻¹) and specific growth rates (range: 3.54–4.34%) also differed significantly among stocking densities, both increasing with decreasing stocking density. The feed conversion ratio in the cages did not differ among the stocking densities, ranging from 1.53 to 1.65. The relationship between stocking density and mean individual weight at harvest followed the equation y =81.06 x ^−0.54 ( R ²=0.938) and that of stocking density and production (in g m⁻²) is y =58.01 x ^−0.46 ( R ²=0.834).     

Effects of Lactobacillus pentosus on the growth performance,digestive enzyme and disease resistance of white shrimp,Litopenaeus vannamei (Boone, 1931)

The objective of this study was to evaluate the probiotic properties of lactic acid bacteria (LAB) strains isolated from digestive tract of white shrimp Litopenaeus vannamei. Eighteen LAB colonies were isolated and one bacterium was found capable of producing three extracellular enzymes (protease, cellulose and lipase) simultaneously and exhibited antagonistic activity against shrimp pathogens (Vibrio vulnificus, V. rotiferianus and V. campbellii). The putative probiotic strain AS13 was identified as Lactobacillus pentosus based on 16S rRNA sequencing. The L. vannamei were fed diet containing 0 (control), 10⁶, 10⁷ and 10⁸ CFU g^?1 bacterial cells of AS13 for 28 days. The results showed that supplementation of L. pentosus significantly improved the growth performance and feed utilization in the treated groups over the control. Similarly, digestive enzyme activities were elevated in the intestines of treated groups. Moreover, feeding of supplemented diets containing AS13 significantly reduced the mortality rate caused by pathogenic Vibrio species (V. vulnificus, V. rotiferianus and V. campbellii). Our results indicated L. pentosus AS13 addition at 10⁷ CFU g^?1 can effectively enhance the growth performance, feed utilization, digestive enzymes and disease resistance of L. vannamei in the laboratory condition.     

Response of biota to aeration rate in low water exchange ponds farming white shrimp, Penaeus vannamei Boone

The response of phytoplankton, zooplankton and benthos to four aeration rates was evaluated in ponds farming white shrimp, Penaeus vannamei Boone, with less than 5% water exchange. Phytoplankton biomass (measured as chlorophyll-fl) was higher in ponds with aeration rates of 0 and 6 h day^?1 than in those with rates of 24 hday^?1. The abundance of zooplankton and benthos (organisms m^?2) were higher in ponds with aeration rates of 0 and 6 h day^?1, and lower in ponds with rates of 12 and 24 h day^?1. The nauplii of different crustaceans, copepods and larval polychaetes were the most abundant organisms of the zooplankton community. Differences in zooplankton composition were observed among treatments. Polychaetes were the most abundant benthic organisms during the culture period. These organisms were more abundant in ponds with lower aeration rates. The guts of shrimp from ponds with aeration rates of 0 and 6 h day^?1 had a higher abundance of zooplankton and benthic organisms than those from the other treatments. That abundance decreased over time in all treatments. Shrimp had better growth in ponds with an aeration of 6 hday^?1. Survival and yield were similar in ponds with aeration rates of 6, 12 and 24 h day^?1, and lower in ponds with rates of 0 h day^?1.     

南美白对虾与罗非鱼混养试验

近两年,由于南美白对虾养殖面积不断增加,池塘老化、种质退化和养殖病害的猖獗,造成虾池养殖经济效益大幅度下降,养殖风险不断增大,大部分养虾户出现亏损,严重影响我省对虾养殖业的发展.在这种情况下,笔者进行了南美白对虾与罗非鱼混养试验,结果表明:混养能够增强养殖水体的自净能力,阻断虾病的蔓延,具有较高的经济效益.     

Polyculture of western white shrimp,Litopenaeus vannamei Boone, 1931 with Grey mullet,Mugil cephalus Linnaeus, 1758 controls external parasites of western white shrimp

The main aim of this study was to examine the effects of a polyculture system on the control of the external parasites of western white shrimp, Litopenaeus vannamei. To this end, the western white shrimp postlarvae (PLs) were stocked in nine earthen ponds (600 m²) at a density of 20 PLs m^?2 and reared for 4 months. After 40 days of shrimp stocking, Mullets, Mugil cephalus, were stocked at various densities including: control (0 fish/100 m² pond), treatment 1 (T₁: 2 fish/100 m² pond) and treatment 2 (T₂: 4 fish/100 m² pond). Over the course of the experiment, the external parasites of shrimps were investigated by the preparation of a wet mount from the gill tissue. Based on the obtained results, totally two genera of protozoan parasites, i.e. Zoothamnium sp. and Epistylis sp., were identified over the course of the experiment. In all experimental groups, the incidence and abundance of Zoothamnium sp. was significantly higher than Epistylis sp. (P < 0.05). Also, mean incidence per cent and mean abundance of Zoothamnium sp. and Epistylis sp. were significantly lower in the polyculture treatments (T₁ and T₂) compared to the monoculture group (control) (P < 0.05). Throughout this experiment, the total organic matter (TOM %) content of the bottom sediments and biological oxygen demand (BOD₅ mg L^?1) of water samples in the polyculture ponds were significantly lower than the monoculture group (P < 0.05). In contrast, the polyculture ponds had a higher concentration of water dissolved oxygen (O₂ mg L^?1) compared to the monoculture (P < 0.05). In conclusion, our results show that mullet as a secondary farmed species can reduce indirectly the parasitic pollution of western white shrimp probably through reducing the total organic matters in water and sediments and improving the water quality parameters.