Litopenaeus Vannamei Postlarvae Research Articles

EFFECT OF PROBIOTIC AND SUPPLEMENTED FEED ON GROWTH, SURVIVAL AND DISEASE RESISTANCE OF WHITE SHRIMP LITOPENAEUS VANNAMEI POSTLARVAE

The present investigation was focused on the effect of Bacillus megaterium enriched to the Artemia nauplii and sprayed on the supplemented feed was fed to the white shrimp Litopenaeus vannamei postlarvae (PL) to obtain high survival and growth. Artemia nauplii enriched with different levels of B. megaterium (5×107, 5×109 and 5×1011 cfu /mL) fed to postlarvae for a period of 30 days. Similarly, supplemented feed with probiotic of different levels fed to PL for a time period of 15 days. Postlarvae fed with 5×109 cfu cells (E2) of B. megaterium enriched Artemia nauplii and supplemented feed produce better survival and growth when compared to that of other concentrations and control group. The specific growth rate was found to be maximum in postlarvae fed with B. megaterium enriched Artemia and supplemented feed when compared to the control group. The biochemical constituents, such as protein, lipid and carbohydrate contents were considerably more in PL fed with both feeds, particularly at 5×109 cfu cells. In the challenging study, results showed a higher survival rate in postlarvae fed with enhanced Artemia nauplii and supplemented feed of E2. Therefore, it is evident that 5×109 cfu cells of B. megaterium can be considered as an appropriate concentration for the growth and survival of L. vannamei postlarvae.

Comparative Genomic Analysis of Seven Vibrio alginolyticus Strains Isolated From Shrimp Larviculture Water With Emphasis on Chitin Utilization.

The opportunistic pathogen Vibrio alginolyticus is gaining attention because of its disease-causing risks to aquatic animals and humans. In this study, seven Vibrio strains isolated from different shrimp hatcheries in Southeast China were subjected to genome sequencing and subsequent comparative analysis to explore their intricate relationships with shrimp aquaculture. The seven isolates had an average nucleotide identity of ≥ 98.3% with other known V. alginolyticus strains. The species V. alginolyticus had an open pan-genome, with the addition of ≥ 161 novel genes following each new genome for seven isolates and 14 publicly available V. alginolyticus strains. The percentages of core genes of the seven strains were up to 83.1–87.5%, indicating highly conserved functions, such as chitin utilization. Further, a total of 14 core genes involved in the chitin degradation pathway were detected on the seven genomes with a single copy, 12 of which had undergone significant purifying selection (dN/dS < 1). Moreover, the seven strains could utilize chitin as the sole carbon-nitrogen source. In contrast, mobile genetic elements (MGEs) were identified in seven strains, including plasmids, prophages, and genomic islands, which mainly encoded accessory genes annotated as hypothetical proteins. The infection experiment showed that four of the seven strains might be pathogenic because the survival rates of Litopenaeus vannamei postlarvae were significantly reduced (P < 0.05) when compared to the control. However, no obvious correlation was noted between the number of putative virulence factors and toxic effects of the seven strains. Collectively, the persistence of V. alginolyticus in various aquatic environments may be attributed to its high genomic plasticity via the acquisition of novel genes by various MGEs. In view of the strong capability of chitin utilization by diverse vibrios, the timely removal of massive chitin-rich materials thoroughly in shrimp culture systems may be a key strategy to inhibit proliferation of vibrios and subsequent infection of shrimp. In addition, transcontinental transfer of potentially pathogenic V. alginolyticus strains should receive great attention to avoid vibriosis.

Survival, osmoregulatory and hemocyte changes in Litopenaeus vannamei postlarvae acclimated to different intervals of salinity reduction

The goal of this study was to assess osmotic stress in Litopenaeus vannamei postlarvae (PL12) in three different progressive osmotic stress levels ranging from sea water (35‰) to low salinity (5‰). The survival of PL12 reduced as medium salinity decreased. PL12 acclimated to a gradual acclimation of 5‰ showed significantly higher survival (with a survival percentage (SP) of 90%) than those acclimated to a gradual acclimation of 10‰ (SP = 80%) and 15‰ (SP = 58%). At the end of the acclimation period (at 5‰), PL12 acclimated to a gradual acclimation of 15‰ (Trial 3) exhibited significantly greater hemolymph osmolality (696 mOsm/kg H2O) than those gradually acclimated to a gradual acclimation of 10‰ (546 mOsm/kg H2O, Trial 2) and 5‰ (450 mOsm/kg H2O, Trial 1). The levels of Na+, K+ and Cl- in the hemolymph of PL12 decreased with decreasing salinity in all three trials. Na+-K+-ATPase levels of PL12 increase as salinity decreases. Total hemocyte count levels decreased when the salinity decreased from 35‰ to 5‰. The longer acclimation time may account for the greater survival rate, as it likely ensures ion balance between the shrimp hemolymph and the surrounding environment thus minimizing osmoregulatory stress.

Bacterial composition and inferring function profiles in the biofloc system rearing Litopenaeus vannamei postlarvae at a low salinity

This study investigated the bacterial composition and inferring function profiles in the biofloc system rearing Litopenaeus vannamei postlarvae (PL) at a low salinity condition. PL (~ stage 15) were stocked in four parallel tanks filled in water with a salinity of 5.0‰ at a density of 4000 individuals per m3 for a 28-days culture experiment, during which glucose was added as a carbon source with a C:N of 20:1. At the end of the experiment, water was sampled from each tank and pooled to extract microbial DNA for high-throughput sequencing of the V3-V4 region of the 16S rRNA gene. Results showed that the bacterial community at 28 d was dominated by phyla of Proteobacteria (45.8%), Bacteroidetes (21.1%), Planctomycetes (13.5%), Chlamydiae (10.3%), and Firmicutes (6.8%). A proportion of 81% inferring KEGG functions of this bacterial community is associated with metabolism. Among functions relating to nitrogen metabolism, 48.5% were involved in converting ammonia to glutamate. Still, the proportion of those engaged in transformation among ammonia, nitrite, and nitrate was 18.0%, inferring higher protein-synthesis but lower inorganic nitrogen-transformation capacities of the bacterial community. At the same time (28 d), high levels of total nitrogen (231.3±6.0 mg L-1) and biofloc (127.0±63.0 mL L-1) but low concentrations of ammonia (0.04±0.01 mg L-1), nitrite (0.2±0.1 mg L-1) and nitrate (12.9±2.5 mg L-1) were observed. The results supply a novel insight for understanding bacterial community function in the biofloc system nursing L. vannamei PL at low salinity.

Estimating the Nanobubble Aerated System and Stocking Density Effects on Oxygen Consumption and Survival of Litopenaeus vannamei (Boone, 1931) Postlarvae 8 Using Receiver Operating Characteristic (ROC) Analysis

Litopenaeus vannamei postlarvae (PL) 8 were usually stocked at high densities, affecting the shrimp and water quality. This condition makes stocking density becomes a challenge in shrimp cultures, and one of the solutions for this is using a nanobubble aerated system. Meanwhile, there is a lack of robust studies estimating the nanobubble and stocking density effects on shrimp survival and water quality. This study used different stocking densities of 200, 400, and 600 postlarvae/L under nanobubble treatment and control (without nanobubble) to culture L. vannamei PL 8 and were assessed using Receiver Operating Characteristic (ROC) analysis. The ROC showed that the values of area Under the Curve (AUC) for dissolved oxygen (DO), survival rates, and oxygen consumption were 0.826 (95%CI: 0.598-1.000), 0.722 (95%CI: 0.47-0.794), and 0.576 (95%CI: 0.28-0.873), respectively. Considering these AUC values, it can be concluded that nanobubble treatment has the possibility to affect DO and shrimp survival, although it is not the same for shrimp oxygen consumption because it has the lowest AUC values. The optimum values for DO, survival rates, and oxygen consumption of shrimp under nanobubble treatment were observed at densities of 400 postlarvae/L. The survival and oxygen consumption of L. vannamei PL 8 at this density were 96.83% (95%CI: 95.2-98.4) and 0.52 mg/g/h (95%CI: 0.46-0.57). Meanwhile, water DO, temperature, and EC were 4.08 mg/L (95%CI: 2.84-5.32), 27.27°C (95%CI: 27.30-27.40), and 1.43 mS/cm (95%CI: 1.40-1.46), respectively. Nanobubble has maintained DO and temperature in the suitable range for L. vannamei PL8 survival.

Artemia nauplii enriched with archaea Halorubrum increased survival and challenge tolerance of Litopenaeus vannamei postlarvae

The red archaea contain carotenoids in their cell membrane, including lycopene, β-carotene and bacterioruberin, etc. Bacterioruberin is a novel bioactive compound, and is considered potential feed additives in food industry and aquaculture. In this study, the carotenoids containing archaea were applied in aquaculture for the first time. Halorubrum (Hrm) strain isolated from brine water was fermented in the culture medium. Hrm cells were fed to Litopenaeus vannamei postlarvae (PL) through Artemia enrichment. Considering the lack of fatty acids in Halorubrum, Artemia enriched with PUFA- riched microalgae Phaeodactylum tricornutum (Pht), and the mixture of Hrm and Pht (Hrm/Pht, 1/1) were included in the experiment. Starved Artemia was conducted as a control (Ctrl). The enrichment was performed at 28 °C for 12 h and at salinity 50 g L−1. The Artemia density was 200 nauplii mL−1 and the amount of enrichment agent was 0.3 g DW L−1. The results showed that the PLs in Hrm group had a better survival and growth when compared with other groups although no significant difference was observed (P>0.05). The PLs in Hrm and Hrm/Pht group had better salinity tolerance than the others. When exposed to the ammonia stress for 48 h, the PLs fed Hrm-enriched Artemia had significantly higher survival percentage than other groups (P<0.05). The content of malondialdehyde (MDA) in the hepatopancreas of ammonia stressed shrimps was significantly lower in enrichment group than the Ctrl group. Our study revealed that the supplementation of Halorubrum had positive effect on the osmotic stress and ammonia stress tolerance in L. vannamei, which is related to the dietary supplementation of Halorubrum, and might be linked to the antioxidative capacity of bacterioruberin existed in the archaeal cells. The present results suggested that red halophilic archaea Halorubrum could be high value feed additive in shrimp larviculture.

Comparing RAS with and without biofloc: Transcriptional response of immune-related genes in Litopenaeus vannamei post-larvae

Background: Shrimp farming is evolving from semi-intensive to hyper-intensive systems with biofloc technology and water recirculation systems. Objective: To evaluate the transcriptional response promoted by biofloc on shrimp (Litopenaeus vannamei) under a recirculating aquaculture system (RAS). Methods: Quantitative real-time RT-PCR was used to monitor seven key genes related to the immune system in shrimp post-larvae, reared in a RAS with and without biofloc (BF and noBF). In addition, we present for the first time nucleotide sequences of ADP-ribosylation factor 4 (LvArf4) from Litopenaeus vannamei. Results: Transcripts for penaeidin3 (Pen3), penaeidin4 (Pen4), crustin, and Toll receptor (LvToll) genes were upregulated between 3 and 24 h in both systems, and tumor necrosis factor receptor-associated factor 6 (TRAF6) in no-BF as an early response. Regarding differential expression between treatments, 13 occurrences were encountered. Nine that were higher in BF than in no-BF and four higher in no-BF than in BF. In some sample times, expression of Pen3, crustin, LvToll, TRAF6, IMD, and LvArf4 was higher in BF than in no-BF and in others, expression of Pen3, Pen4, and TRAF6 was higher in no-BF than in BF. Conclusions: BF modulates the transcription of genes related to the immune response in shrimp as an early response. However, the RAS with no-BF promotes a similar response.Keywords: antimicrobial peptide; aquaculture; biofloc; gene expression; Penaeidin; RAS; shrimp; shrimp immune system. Resumen Antecedentes: Los cultivos de camarón están evolucionando de sistemas semi-intensivos a hiper-intensivos con biofloc y con recirculación. Objetivo: Evaluar la respuesta transcripcional promovida por el biofloc en un sistema acuícola con recirculación (SAR). Métodos: Monitoreamos mediante RT-PCR cuantitativo siete genes relacionados con el sistema inmune en postlarvas de camarón cultivadas en un SAR con y sin biofloc (BF y no-BF). Además, presentamos por primera vez la secuencia de nucleótidos del factor de ribosilación 4 de ADP (LvArf4) de Litopenaeus vannamei. Resultados: Los genes penaeidina3 (Pen3), penaeidina4 (Pen4), Crustina y Toll (LvToll) se sobre-expresaron entre las 3 y 24 h en ambos sistemas, y el factor 6 asociado al factor de necrosis tumoral (TRAF6) en BF como una respuesta temprana. Con respecto a la expresión diferencial entre los tratamientos, se presentaron 13 ocurrencias. Nueve donde el BF fue mayor que sin-BF y cuatro donde el no-BF fue mayor que el BF. La expresión fue más alta en BF que en no-BF en Pen3, Crustin, LvToll, TRAF6, IMD y LvArf4. En contraste, la expresión fue mayor en no-BF en Pen3, Pen4 y TRAF6. Conclusiones: el BF modula la transcripción de los genes relacionados con la respuesta inmune en camarón como una respuesta temprana. Sin embargo, el SAR sin-BF promueve una respuesta similar.Palabras clave: aquicultura; biofloc; camarón; expresión genética; Penaeidina; péptido antimicrobiano; SAR; sistema inmune de camarón. Resumo Antecedentes: A criação de camarões está evoluindo de sistemas semi-intensivos para hiper-intensivos como tecnologia de bioflocos e sistemas de recirculação. Objetivo: Avaliar a resposta transcricional promovida pelo biofloco em um sistema de aquicultura recirculante (SAR). Métodos: Utilizamos RT-PCR quantitativo em tempo real para monitorar sete genes-chave relacionados ao sistema imune em pós-larvas de camarão, criados em SAR com e sem bioflocos (BF e no-BF). Além disso, apresentamos pela primeira vez sequências nucleotídicas do fator de ribosilação do ADP 4 (LvArf4) de Litopenaeus vannamei. Resultados: Os resultados mostraram que o Penaeidina3 (PEN3), Penaeidina4 (Pen4), Crustina e Toll genes (LvToll) foram sobre-expressos entre 3 e 24 h em ambos os sistemas, e o Factor de Necrose do Receptor 6 associado e protuberância (TRAF6) no BF como uma resposta precoce. Com relação à expressão diferencial entre tratamentos, 13 ocorrências foram apresentadas. Nove onde o BF foi maior do que os não-BF e quatro onde o não-BF foi maior do que o BF. A expressão foi maior do que em BF não-BF em Pen3, Crustin, LvToll, TRAF6, IMD e LvArf4. Em contraste, a expressão foi mais elevada no não-BF em Pen3, Pen4 e TRAF6. Conclusões: O BF modula a transcrição de resposta imune relacionada no camarão como um genes de resposta precoce. No entanto, o SAR não BF promove uma resposta semelhante.Palavras-chave: aquicultura; biofloco; camarão; expressão genética; Penaeidina; peptídeo antimicrobiano; SAR; sistema imunológico do camarão.

Effects of enriched Artemia with n–3 long-chain polyunsaturated fatty acids on growth performance, stress resistance and fatty acid profile of Litopenaeus vannamei postlarvae

A 15-day study was conducted to evaluate the effects of Artemia metanauplii enriched with two commercial supplements (Easy DHA-Selco and S. presso) which contained high levels of n–3 long chain polyunsaturated fatty acids (n–3 LC-PUFA) on growth performance, stress resistance and fatty acid profile of Litopenaeus vannamei post larvae (PL). In this regard, PL were fed with three different types of Artemia including: (1) newly hatched Artemia franciscana nauplii as the control group; (2) Artemia metanauplii enriched with Easy DHA-Selco; and (3) Artemia metanauplii enriched with S. presso. Survival rates did not change among different groups. PL fed Artemia enriched with the S. presso and the Easy DHA-Selco showed the highest wet and dry weight, respectively (p<0.05). Moreover, PL fed Artemia enriched with the commercial emulsions had higher survival rate (~ 10 %) than treatments fed newly hatched Artemia (p<0.05).The concentration of n–3 PUFA especially DHA and also n-3 / n-6 PUFA ratios were higher in PL fed with Artemia enriched with the commercial emulsions than the control group. Feeding enriched Artemia with n–3 LC-PUFA is recommended to improve growth performance in larval stages of L. vannamei.

Integrating different densities of white leg shrimp Litopenaeus vannamei and red seaweed Gracilaria tenuistipitata in the nursery phase: effects on water quality and shrimp performance

The effects of integrating different densities of white leg shrimp Litopenaeus vannamei postlarvae (PL) and red seaweed Gracilaria tenuistipitata on water quality and shrimp performance were assessed in the nursery phase. A 3 × 4 factorial experiment with three levels of shrimp density (1000, 2000, and 3000 PL m−3) and four levels of red seaweed density (0, 1.0, 1.5, and 2.0 kg m−3) was randomly designed in triplicate. Shrimp PL12 (mean weight of 4.27 ± 0.28 mg) and red seaweed were stocked in 150-L tanks at a salinity of 15 g L−1 for 30 days. The results indicated that the integration of shrimp PL and red seaweed significantly reduced the nitrogen and phosphorus contents in the culture tanks and improved the survival and growth rate of shrimp, although not significantly. A significant interaction effect (p < 0.01) between shrimp and seaweed densities was only observed for shrimp production. Notably, higher stocking density resulted in lower growth performance but enhanced production. Applying stocking densities of 1000 and 2000 PL m−3 reared shrimp that were bigger in size, while a density of 3000 PL m−3 obtained the highest production output in the integrated system. Following the 30-day growth trial, shrimp quality was examined through a bacterial challenge test using pathogenic Vibrio parahaemolyticus on the shrimp groups previously reared at a density of 3000 PL m−3 and integrated with different amounts of seaweed. After 14 days of immersion challenge, the cumulative mortality in the control group was significantly higher than that of other groups. This result suggests that the presence of G. tenuistipitata improved the antibacterial activity of L. vannamei against V. parahaemolyticus during the nursery phase.

Managing input C/N ratio to reduce the risk of Acute Hepatopancreatic Necrosis Disease (AHPND) outbreaks in biofloc systems – A laboratory study

Biofloc systems are microbial mature environments that are potentially less conducive disease outbreaks. We hypothesized that the way in which biofloc microbial communities are managed determines the level of disease protection. To investigate such hypothesis, Litopenaeus vannamei post-larvae were cultured for 21 days in biofloc environments created by different water management procedures. Five different types of bioflocs were created: autotrophic bioflocs without probiotics, autotrophic bioflocs with probiotics, heterotrophic bioflocs without probiotics, heterotrophic bioflocs with probiotics, and a flow-through system as a control. Heterotrophic bioflocs were obtained by daily addition of carbon (glucose) at an estimated C/N ratio of 18 throughout the experiment. For autotrophic bioflocs this input of carbon was applied only to start up the system and upon appearance of bioflocs (TSS > 100 mg L−1) and a drop in total ammonium nitrogen concentration below 0.05 mg L−1, carbon dosing was stopped. Bioflocs cultured with addition of probiotics received a 0.5 ppm dose every 48 hours. After 21-d culture period, a 96 h challenge test was performed with a Vibrio parahaemolyticus strain known to cause AHPND. For each biofloc type, this challenge was performed in three different approaches: 1- Shrimp were taken out of their biofloc tanks and challenged by applying new seawater; 2-Shrimp from biofloc tanks were challenged in their respective biofloc suspensions; and 3- Non-experimental shrimp, randomly selected from a recirculation (RAS) system were challenged in the types of biofloc suspensions. Mortality was high when shrimp were challenged in new seawater, independent of treatment. When challenged in their respective biofloc suspensions shrimp survival was the highest in heterotrophic bioflocs with and without probiotic supplementation and the autotrophic bioflocs with probiotics, whereas shrimp survival in autotrophic bioflocs without probiotics was 50%. These results were similar when non-experimental shrimp originating from a RAS system were challenged in these biofloc suspensions. Taken together, results suggest that bioflocs as such can decrease the impact of a Vibrio parahaemolyticus challenge and that this protection depends on the operational parameters of the biofloc system. Moreover, probiotics can be used to complement the protective effect of bioflocs. This information reinforces the importance of microbial community management as a tool to reduce the risk of disease and establish highly biosecure systems.

Efficacy assessment of commercially available natural products and antibiotics, commonly used for mitigation of pathogenic Vibrio outbreaks in Ecuadorian Penaeus (Litopenaeus) vannamei hatcheries

Bacterial diseases cause high mortality in Penaeus (Litopenaeus) vannamei postlarvae. Therefore, appropriate application of efficient therapeutic products is of vital importance for disease control. This study evaluated through in vitro analyses the antimicrobial effectiveness of commercial therapeutic products used for P. vannamei bacterial diseases and antibiotics against pathogenic Vibrio strains circulating in Ecuadorian hatcheries. Twenty strains were isolated from 31 larvae samples with high bacterial counts from 10 hatcheries collected during mortality events. The strains virulence was verified through challenge tests with Artemia franciscana nauplii and P. vannamei postlarvae. Through 16S rRNA sequence analysis, strains showed a great similarity to the Vibrio sequences reported as pathogens, with 95% belonging to the Harveyi clade. Through antibiograms and minimal inhibitory concentration (MIC) in vitro tests we found that furazolidone, ciprofloxacin, chloramphenicol, norfloxacin, nalidixic acid, florfenicol, fosfomycin and enrofloxacin inhibited the growth of all or most of the strains. Less efficient antibiotics were penicillin, oxytetracycline and tetracycline. A multiple antibiotic resistance (MAR) index of 0.23 showed some level of resistance to antibiotics, with two MAR prevalent patterns (Penicillin-Oxytetracycline and Penicillin-Oxytetracycline-Tetracycline). From a total of 16 natural products (five probiotics, nine organic acids and two essential oils), only three (one probiotic, one organic acid and one essential oil) were effective to control most of the strains. Shrimp producers can apply relatively simple in vitro analyses, such as those employed in this study, to help take adequate management decisions to reduce the impact of bacterial diseases and increase profit.

Effect of different concentrations of potassium and magnesium on performance of Litopenaeus vannamei postlarvae reared in low-salinity water and a biofloc system

ABSTRACTEffect of K+ and Mg2+ in water on the performance of Litopenaeus vannamei using bioflocs was evaluated. Control had water with K:Mg (1:4.57) and other treatments (K:Mg of 1:5.4, 1:4.65, and 1:3.77), both with salinity of 4 g/L. Initial mean weight of shrimp was 0.08 ± 0.007 g. No difference in shrimp growth performance and survival was observed (P > 0.05) except in the control. Our results suggest that it is possible to culture postlarvae of Litopenaeus vannamei in low-salinity water with bioflocs when the water has an initial potassium concentration of 30.90 ± 8.5 mg/L and magnesium of 167.0 ± 3.9 mg/L.

Poly-β-hydroxybutyrate (PHB)-accumulating Halomonas improves the survival, growth, robustness and modifies the gut microbial composition of Litopenaeus vannamei postlarvae

The PHB-accumulating Halomonas strain was isolated from local solar saltworks and was cultured in CM culture medium with addition of 30 g L−1 glucose to favor the PHB accumulation in the cells. The effect of Halomonas-PHB on the survival, growth, osmotic stress tolerance, resistance against Vibrio anguillarum challenge and the gut microbial composition of Litopenaeus vannamei postlarvae were investigated. The postlarvae PL6 were fed Artemia nauplii enriched with Halomonas-PHB (HM.PHB), Halomonas without PHB accumulation (HM), commercial PHB particles (par.PHB) and non-enriched Artemia nauplii (Control), respectively, for two weeks. The results revealed that both Halomonas-PHB and particle PHB could improve the survival, growth, and enhance the robustness of the shrimp PLs under both challenge and non-challenged conditions. High throughput sequencing on gut microbiota indicated that Halomonas-PHB not only suppressed the propagation of Vibrio, but also diverged to gut microbiota towards to the probiotic bacteria propagation (i.e. Bacillus and Lactobacillus) in the gut. In conclusion, the Halomonas-PHB is more efficient than particle PHB in L. vannamei larviculture and thus can be applied as feed additive in shrimp culture.

Enriched Artemia with L-lysine and DL-methionine on growth performance, stress resistance, and fatty acid profile of Litopenaeus vannamei postlarvae

ABSTRACTA 15-day study was conducted to evaluate the effect of enrichment of Artemia metanauplii with four different emulsions, including: (A) Easy-DHA Selco; (B) Easy-DHA Selco + L-lysine (4 g/L); (C) Easy-DHA Selco + DL-methionine (4 g/L); and (D) Easy-DHA Selco + L-lysine (2 g/L) + DL-methionine (2 g/L) on growth and stress resistance of white leg shrimp Litopenaeus vannamei larvae (from Mysis I to postlarvae12). It is noticed that shrimp PL in group B had the highest wet (36.1 ± 3.1 mg) and dry (1116.7 ± 60.0 µg) weights as well as stress resistance to fresh water (64.0 ± 5.5%).

Erratum to: Effects of dietary botanical and synthetic astaxanthin on E/Z and R/S isomer composition, growth performance, and antioxidant capacity of white shrimp, Litopenaeus vannamei, in the nursery phase

Astaxanthin (AST) is a beneficial dietary supplement in shrimp farming. However, the different effects of synthetic AST (S-Ast) and natural AST (N-Ast) on the postlarvae is unclear. These effects were compared by supplementation with a gradient of AST (0, 50, 70, 90, 140 ppm) for 35 days. Growth parameters including weight and length gain, carotenoid content, AST content and isomer composition, antioxidant capacity (superoxide dismutase, catalase, glutathione peroxidase), survival rate and mRNA expression levels for antioxidant enzymes in Litopenaeus vannamei postlarvae were measured. The results indicated that postlarvae given N-Ast had significantly higher growth performance and AST content. Although there were different ratios of AST optical isomers in the diets, there was a similar optical isomer content in juvenile shrimp. The cis/trans AST ratio and antioxidant enzyme (SOD and GPx) activities in N-Ast90 were the highest among all groups. Cumulative mortality in N-Ast90, N-Ast140 and S-Ast70 were significantly lower than in the control and N-AST50. The mRNA expression levels for the antioxidant enzymes (cMnSOD and GPx) also increased for N-Ast90-fed shrimp under stress conditions. These results suggest that an epimerase may exist in vivo and that an appropriate level of botanical AST in diets was approximately 90 ppm for L. vannamei postlarvae.

Acute Toxicity of Ammonia, Nitrite and Nitrate to Shrimp Litopenaeus vannamei Postlarvae in Low-Salinity Water.

Shrimp farming in low salinities waters is an alternative to increasing production, and counteracting disease problems in brackish and marine waters. However, in low-salinity waters, toxicity of nitrogen compounds increases, and there is no available data of its acute toxicity in shrimp postlarvae. This study determined the acute toxicity of ammonia, nitrite and nitrate in Litopenaeus vannamei postlarvae in 1 and 3g/L salinity, as well as the safety levels. The LC50 confirms that nitrite is more toxic than ammonia and nitrate in low salinity waters, and that its toxicity increases with a decrease in salinity. The safe levels estimated for salinities of 1 and 3g/L were 0.54 and 0.81mg/L for total ammonia-N, 0.17 and 0.25mg/L for NO2-N, and 5.6 and 21.5mg/L for NO3-N, respectively.

Effects of dietary botanical and synthetic astaxanthin on E/Z and R/S isomer composition, growth performance, and antioxidant capacity of white shrimp, Litopenaeus vannamei, in the nursery phase [For this article an Erratum has been published

Astaxanthin (AST) is a beneficial dietary supplement in shrimp farming. However, the different effects of synthetic AST (S-Ast) and natural AST (N-Ast) on the postlarvae is unclear. These effects were compared by supplementation with a gradient of AST (0, 50, 70, 90, 140 ppm) for 35 days. Growth parameters including weight and length gain, carotenoid content, AST content and isomer composition, antioxidant capacity (superoxide dismutase, catalase, glutathione peroxidase), survival rate and mRNA expression levels for antioxidant enzymes in Litopenaeus vannamei postlarvae were measured. The results indicated that postlarvae given N-Ast had significantly higher growth performance and AST content. Although there were different ratios of AST optical isomers in the diets, there was a similar optical isomer content in juvenile shrimp. The cis/trans AST ratio and antioxidant enzyme (SOD and GPx) activities in N-Ast90 were the highest among all groups. Cumulative mortality in N-Ast90, N-Ast140 and S-Ast70 were significantly lower than in the control and N-AST50. The mRNA expression levels for the antioxidant enzymes (cMnSOD and GPx) also increased for N-Ast90-fed shrimp under stress conditions. These results suggest that an epimerase may exist in vivo and that an appropriate level of botanical AST in diets was approximately 90 ppm for L. vannamei postlarvae.

Effect of 17β-Estradiol on Feminization, Growth Rate and Survival Rate of Pacific White Shrimp (Litopenaeus vannamei, Boone 1931) Postlarvae

This study was therefore aimed to determine the effect of different concentration of estrogen hormone, 17β-estradiol (E 2 ) on feminization for the production of all female, growth rate and survival rate of Pacific white shrimp ( Litopenaeus vannamei ) postlarvae (PL). L. vannamei PL 1 were stocked randomly at a density of 10 ind.L -1 into a 10 L of seawater for each experimental flask with three replicates each. PL 1 was immersed in seawater containing 0.5, 1.0 and 1.5 mg.L -1 estrogen hormone, E 2 for 4 hours. The experiment was continued for 30 days for larval rearing. At the termination of experiment, the specimens in each treatment groups were weighed and measured individually for their wet body weight (BW) and total length (TL) for the mean weight gain, length gain, and the specific growth rate (SGR) estimation. The mean sex ratio values of male to female postlarvae obtained from control till the highest E 2 hormone concentration of 0, 0.5, 1.0 and 1.5 mg.L -1 were 1:1, 1:2, 1:9 and 0:1 respectively. The weight gain and length gain were 40605% and 606% for control, 46310% and 647% for 0.5 mg.L -1 concentration, 49310% and 663% for 1.0 mg.L -1 concentration and 45048% and 628% for 1.5 mg.L -1 . The mean SGR BW and SGR TL for control till the highest E 2 hormone concentration of 0, 0.5, 1.0 and 1.5 mg.L -1 were 20.00 and 6.51, 20.46 and 6.70, 20.67 and 6.77 and 20.37 and 6.62 respectively. The mean survival rate for E 2 hormone concentration of 0, 0.5, 1.0 and 1.5 mg.L -1 were 52.67%, 54.33%, 54.67% and 52.33% respectively. The study shows that while the concentration of E 2 hormone increased, the female sex ratio of L. vannamei PL also increased but the growth rate and survival rate decreased at concentration of 1.5 mg.L -1 . Thus the optimum concentration of this hormone usage was 1.0 mg.L -1 immersed for 4 hours. Keywords: 17β-estradiol, feminization, growth rate, Litopenaeus vannamei , postlarvae, survival rate.

Comparison of four treatments to evaluate acute toxicity of nitrite in shrimp Litopenaeus vannamei postlarvae: Influence of feeding and the renewal water

Distincts methods are used to evaluate acute toxicity and generate different values of LC50. However, the static with renewal (100% renewal every 24h) and feeding method is the more utilized. This study was developed to determine the differences between the LC50 obtained and define which method is most adequate for testing acute toxicity of nitrite in shrimp. Litopenaeus vannamei postlarvae (PL18) were exposed to different concentrations of nitrite-N (nitrite as nitrogen) at 3g/L of salinity, using two different strategies of renewal solution and feeding trials: treatment Ts/nf/1 (static (no water renewal)+not feed), Tsr/f/2 (static with renewal+feed), Tsr/nf/3 (static with renewal+not feed) and Ts/f/4 (static+feed). Different values of LC50 nitrite-N for 96h values were generated for the four distinct treatments (Tsr/f/2>Tsr/nf/3>Ts/nf/1, Ts/f/4). However, significant differences (p<0.05) were only between the treatments that involves feeding and not feeding in the static with renewal method (Tsr/f/2>Tsr/nf/3). Considering the magnitude and variation of the LC50 values, it is recommended the static with renewal method and feeding method which generates higher values of LC50 and lowest variation, results suggesting that this method is more adequate to evaluate in shrimps nitrite and other nitrogen compounds acute toxicity.

Tetraselmis chuii biomass as a potential feed additive to improve survival and oxidative stress status of Pacific white-leg shrimp Litopenaeus vannamei postlarvae

Shrimp is an important traded fishery commodity. When subjected to stress, shrimp usually suffers from oxidative stress, which leads to cell injury, senescence, and death. To maintain shrimp good health, performance and production, antioxidant and immune systems are important. Natural antioxidants found in microalgae may be used to increase the cell protection against oxidative damage, being a promising alternative to the carcinogenic synthetic antioxidants. In this study, Tetraselmis chuii was evaluated for its effect on survival, growth and oxidative stress biomarkers on Litopenaeus vannamei postlarvae (PL). The antioxidant properties of the formulated feed with T. chuii inclusion were determined using four antioxidant chemical assays. Meanwhile, the oxidative stress biomarkers on PL were analyzed by hydrogen peroxide, membrane stability and lipid peroxidation assays. Results showed that PL reared on diets supplemented with 50% T. chuii had a significantly higher (P ≤ 0.05) survival (97.6 ± 1.4%) and lower oxidative stress in terms of hydrogen peroxide content (10.08 ± 0.4 mM g−1 FW) and electrolyte leakage (10.8 ± 0.3%). The result of this study also showed that shrimp PL reared on diets supplemented with microalgal, T. chuii have high resistance to reverse salinity stress test (76.7–100%). However, no significant differences (P ≥ 0.05) were found in the growth and lipid peroxidation. Due to the positive effect on oxidative stress status, survival and resistance to salinity stress, the feeding of L. vannamei PL with diet containing at least 50% of T. chuii is recommended as a natural source of antioxidant for PL.