Juvenile White Shrimp Litopenaeus Vannamei Research Articles

Immunomodulatory effects of PACAP sequence modifications in juvenile white shrimp Litopenaeus vannamei

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a highly conserved multifunctional neuropeptide belonging to the secretin/glucagon/vasoactive intestinal peptide superfamily. In recent years, the role of PACAP in immunoregulation has been partially elucidated in mammals and teleost fishes, demonstrating that PACAP modulates both innate and acquired immunity. However, in invertebrates, little is known about its immunostimulant and antimicrobial properties. In previous research, studies performed in Litopenaeus (Penaeus) vannamei have revealed that Clarias gariepinus PACAP-38 improves immune functions like lectins, superoxide dismutase and nitric oxide synthase derived metabolites in postlarvae shrimp. In this study, the immunomodulatory effects of C. gariepinus PACAP-38 and four PACAP sequence modified peptides in juvenile L. vannamei were evaluated. The effect of several administrations of PACAP and its variants on shrimp immune effectors, as well as the effect of different doses was examined. Results revealed that PACAP can influence hemolymph immune parameters, and immune-related gene mRNA levels in the hemocytes, gill and hepatopancreas with different effects depending on the modification of the peptide sequence, the dose and the tissue assessed. Altogether, these findings provide valuable insights regarding the role of PACAP in crustacean innate immunity and highlight the need for further research into its potential application as an alternative to antibiotics in aquaculture.

Leucine promotes protein synthesis of juvenile white shrimp Litopenaeus vannamei through TOR signaling pathway

Leucine is an essential amino acid for animal growth and development. However, the role of leucine in protein and glucose metabolism in crustaceans remains unclear. In this study, the effects of leucine on TOR pathway and glucose metabolism of Pacific white shrimp (Litopenaeus vannamei) were investigated by a feeding trial and an in vitro experiment. A total of 540 juvenile shrimps (0.67 ± 0.00 g) were randomly distributed into 18 tanks with 30 shrimps per tank. Shrimp were fed 6 diets with leucine levels of 2.10, 2.30, 2.50, 2.70, 2.90 and 3.10% respectively for 56 days (n = 3). The results showed that 2.50% leucine promoted muscle crude protein content, hepatopancreatic fibrillar cell number and area, and decreased serum and hepatopancreas glucose content. It was found that 2.50% leucine significantly up-regulated the expression levels of key genes in the TOR signaling pathway, including protein kinase B (akt), ras homologue enriched in brain (rheb), solute carrier family 3 member 2 (slc3a2), target of rapamycin (tor), regulatory-associated protein of mTOR (raptor), RPTOR independent companion of mTOR, Complex 2 (rictor), rhodopsin (rho), ribosomal protein S6 kinase (s6k) and eukaryotic translation initiation factor 4E 2 (eif4e2), but down-regulated the expression of tuberous sclerosis 2 (tsc2) and 4E-Binding protein (4e-bp) in hepatopancreas, which suggests that leucine may regulate protein deposition through TOR pathway. Similarly, the protein expression of Akt was also increased at 2.50% dietary leucine level. In addition, 2.50% dietary leucine level significantly increased the gene expressions of hexokinase (hk), pyruvate kinase (pk) and glucose transporter 2 (glut2), and down-regulated the gene expressions of pyruvate carboxylase (pc) and phosphoenolpyruvate carboxy kinase (pepck), which indicates appropriate leucine lowers glucose through glycolysis and gluconeogenesis pathway. Furthermore, the in vitro study showedthat 250 mg/L leucine supplement significantly increased hepatopancreas cell viability and up-regulated the expression levels of tor, akt, slc3a2, s6k, eif4e2, rictor, rho, hk, pk, pepck and glut2 compared with the control group (without leucine). The expression level of Sestrin (sesn) in hepatopancreas cells was down-regulated. These results suggest that appropriate dietary leucine supplementation can promote protein deposition of white shrimp, which may be attributed to the fact that leucine can maintain the structural integrity of hepatopancreas and improve protein synthesis and glucose utilization through TOR signaling pathway. The leucine requirement of Litopenaeus vannamei is estimated to be 2.60%–2.67% of the diet (6.67%–6.88% of dietary protein) according to the polynomial regression analysis of whole-body protein, muscle protein, hepatopancreas glucose and hepatopancreatic fibrillar cell number. These results will help us further understand the effects of leucine on growth and protein deposition in crustaceans.

Dietary enrichment with crude protein content and feed additives (Bacillus spp. and yeast strains) improves growth performance, survival and circulating hemocytes in juvenile White shrimp, Litopenaeus vannamei

In this study the enrichment dietary effect with different crude protein levels (CP) and feed additives on growth, survival, feed conversion ratio (FCR), feed consumption (FC) and total hemocyte count (THC) in juvenile white shrimp Litopenaeus vannamei were evaluated. The study covered two bioassays: in the first one, juveniles were daily fed for 45 days with four experimental diets containing: (1) Control, commercial feed (35% CP); (2) 29% CP; (3) 32% CP; (4) 35% CP. After the 29% CP diet was selected, juveniles in bioassay II were daily fed for 45 days with a single CP diet complemented with probiotics: (1) Control, commercial feed (35% CP); (2) 29% CP; (3) 29% CP + Bacillus mix at 1×106 CFUg–1 feed; and (4) 29% CP + yeast mix at 1×106 CFUg–1 feed. Juvenile shrimp fed with experimental diets gained significantly more weight and increased survival, FCR, FC and THC compared with control diet. However, differences among experimental diets were not significant. In bioassay II, juvenile shrimp fed with experimental diet + feed additives significantly increased survival, FCR, FC and THC compared with control diet. Growth of juveniles significantly increased with 29% CP and 29% CP + yeast mix diets, compared with control group. Complementing the diet with yeast mix showed higher survival and THC of juveniles compared with the other experimental treatments. Different CP levels in shrimp diet improved growth, survival and circulating hemocytes, and addition of mixed yeast as feed additive induced better survival and immune response in juvenile shrimp.

Partial replacement of soybean meal with fermented cottonseed meal in a low fishmeal diet improves the growth, digestion and intestinal microbiota of juvenile white shrimp Litopenaeus vannamei

This study investigates the effects of replacing soybean meal with fermented cottonseed meal (FCSM) in low fishmeal diets on the growth performance, antioxidant capacity, immune capacity, digestive enzyme activities and intestinal microbiota of Litopenaeus vannamei. Six isonitrogenous and isolipidic diets were prepared, including the conventional fishmeal (250 g kg−1) group as the control, and the low fishmeal (150 g kg−1) diet used FCSM (0, 105, 210, 315 and 420 g kg−1) to replace 0 % (FCSM0), 25 % (FCSM25), 50 % (FCSM50), 75 % (FCSM75) and 100 % (FCSM100) soybean meal of the diet. Each diet was fed to four replicate groups of shrimp (0.16 ± 0.01 g) for 8 weeks. The results showed that the survival of the FCSM0 group was significantly lower than that of the other groups (P < 0.05). The weight gain and specific growth rate of the FCSM0 group were significantly lower than those of the control and FCSM75 groups (P < 0.05). The crude protein of whole shrimp was significantly decreased in the FCSM75 group compared with the control and FCSM100 groups (P < 0.05). The contents of essential amino acids, nonessential amino acids and total amino acids of L. vannamei in the FCSM25, FCSM50, and FCSM75 groups were significantly higher than those of the control (P < 0.01). The intestinal microbiota sequencing results showed that FCSM increased the microbiota diversity. At the genus level, the FCSM75 group had a lower abundance of Vibrio, Demequina, Microbacterium, Photobacterium and Roseburia than the FCSM0 group. Based on the KEGG functional prediction results, compared with the FCSM0 group, the FCSM75 group significantly upregulated the “glutathione metabolism”, “galactose metabolism”, and “amine and polyamine biosynthesis” pathways in the intestinal microbiota. This study demonstrates that replacing 75% soybean meal with FCSM in a low fishmeal diet could improve the growth performance, antioxidant capacity, and essential amino acid content of L. vannamei.

Effects of Time-Dependent Protein Restriction on Growth Performance, Digestibility, and mTOR Signaling Pathways in Juvenile White Shrimp Litopenaeus vannamei.

A 6-week feeding strategy experiment was conducted to investigate the effects of time-dependent protein restriction and subsequent recovery on shrimp. Diets with protein levels of 43 and 36% were used as adequate and restricted diets, respectively. Shrimp with an initial body weight of 6.52 ± 0.46 g were given four feeding strategies: feeding on an adequate diet for six weeks (T1, the control), having protein-restricted diet in weeks 1 and 4 (T2), being given a protein-restricted diet in weeks 1, 3, and 5 (T3), and having protein-restricted diet in weeks 1, 2, 4, and 5 (T4). WG, SGR, FE, and PER of shrimp in T1–T3 showed no significant difference (P > 0.05), these indicators of T4 were significantly reduced (P < 0.05). No significant differences were found in digestive enzyme activities of shrimp among all treatments (P > 0.05). Crude protein content of shrimp muscle in T4 was lower than that of T1–T3. The expression level of tor in T4 was lower than that in other treatments, while 4e-bp was higher than that of other treatments. To balance saving on feeding cost and growth performance, giving the shrimp a protein-restricted diet for 1 week with subsequent refeeding (T2 and T3) is suitable for shrimp under high-density conditions.

A SNP of the hemocyanin gene (LvHc) is a marker for high growth and ammonia-tolerance in Pacific white shrimp Litopenaeus vannamei

Expression levels of hemocyanin (LvHc), activating transcription factor 4 (LvAtf4), glutathione S-transferase (LvGst), caspase 2 (LvCasp2) and anti-lipopolysaccharide factor (LvAlf) were examined in the hepatopancreas of Pacific white shrimp Litopenaeus vannamei juveniles exposed to a lethal concentration of ammonia-N (32.15 mg/l). The expression levels of all transcripts except LvAlf were significantly greater (P < 0.05) in tolerant shrimp (Lv-AT; N = 30) that survived up to 72 h post treatment (hpt) than in susceptible shrimp (Lv-AS24 and Lv-AS72; N = 45 and 15), that died within 24 h or between 24 and 72 hpt, respectively. Subsequently, effects of non-lethal concentrations of ammonia-N (control, 10 and 20 mg/l) on the expression of LvHc in juvenile shrimp were examined. Compared to the control, expression levels of LvHc transcripts in hemocytes and the hepatopancreas of tested shrimp changed after exposure to ammonia-N. One SNP (C > T545) was found in the LvHc322 gene segment. Real-time PCR amplification of specific alleles (real-time PASA) was developed for detection of C > T545 genotypes. Juveniles in the lethal exposure test that carried a C/T545 genotype showed a greater average body weight and total length (8.46 ± 0.36 g and 10.05 ± 0.16 cm) than those with a C/C545 genotype (7.48 ± 0.31 g and 9.60 ± 0.13 cm) (P < 0.05). Similar results were found in the second generation (G2) of a growth-improved stock (3 and 4 families of BIOTEC-G2-L1 and BIOTEC-G2-L2) and in commercially farmed shrimp (2 groups). Accordingly, expression levels and SNP of LvHc can serve as markers for selection high growth performance in ammonia-tolerant L. vannamei.

Long-term administration of diets containing Gracilaria tenuistipitata extract induce the expression of immune-related genes and increase the immune response and resistance against Vibrio harveyi in white shrimp Litopenaeus vannamei

White shrimp Litopenaeus vannamei juveniles (2.15 ± 0.16 g) fed diets containing Gracilaria tenuistipitata extract (GTE) at 0, 0.5, 1.0, and 2.0 g kg−1 for 16 weeks were examined for transcripts of lipopolysaccharide and β-1,3-glucan binding protein (LGBP), peroxinectin (PX), integrin β (IB), prophenoloxidase (proPO) I, proPO II, α-2 macroglobulin (α-2 M), cytMnSOD, mtMnSOD, glutathione peroxidase (GPx), transglutaminase (TG) I, TG II, lysozyme, and heat shock protein 70 (HSP70) as well as immune parameters. Shrimp fed the 2.0 g kg−1 GTE diet significantly exhibited up-regulated expressions of these genes, increased hyaline cells (HCs), granular cells (GCs, including semi-granular cells), total hemocyte count (THC), phenoloxidase (PO) activity, respiratory burst (RB), superoxide dismutase (SOD) activity, and earlier hemolymph clotting time. In a separate experiment, shrimp fed different diets for 16 weeks were challenged with Vibrio harveyi at 2 × 104 cfu shrimp−1 and then placed in seawater. The survival rate of shrimp fed the 2.0 g kg−1 GTE diet was significantly higher over 24–168 h post challenge. In conclusion, shrimp following long-term oral administration of a GTE-containing diet at 2.0 g kg−1 induced the expression of immune-related genes and exhibited increased their immune response and resistance against V. harveyi.

Correction to: Effect of diets supplemented with different seaweed extracts on growth performance and digestive enzyme activities of juvenile white shrimp Litopenaeus vannamei

The original version of this article unfortunately contained mistakes. Below are the corrections.

Effect of diets supplemented with different seaweed extracts on growth performance and digestive enzyme activities of juvenile white shrimp Litopenaeus vannamei

This study evaluated the nutritional potential of three seaweed extracts (Ulva lactuca, Eisenia sp. and Porphyra sp.) as possible ingredients in shrimp feed to improve growth and main digestive enzyme activities. Seaweed extracts were included in replacement of wheat and soybean meal in isoproteic diets (35 ± 0.5%) at three levels of inclusion (5, 10, and 15%) and tested during 28 days in a feeding trial on Litopenaeus vannamei (initial weight 1.15 ± 0.08 g). Growth performance and feed utilisation parameters, in addition to trypsin, chymotrypsin, lipase and amylase activities, were evaluated. An increase of ash content in experimental diets was observed as seaweed extract inclusion level increased (from 7 up to 13.4%). All shrimps fed with seaweed diets significantly improved (p < 0.01) final weight (FW), weight gain (WG), specific growth rate (SGR) and feed intake (FI) in contrast to control diet. In general, Ulva diets presented the best shrimp growth performance, among which inclusion of 15% Ulva extract resulted in significantly higher FW, WG and SGR (p < 0.01) compared to control, Porphyra and Eisenia diets. In the case of chymotrypsin, lipase and amylase enzyme activity, a significant interaction between seaweed type and inclusion level was found (p < 0.01), where in most cases, inclusion level of 5% of all type of seaweed resulted in an increase of the enzyme activities. The use of any of the three proposed seaweed extracts in balanced feed, especially Ulva, is suggested to promote shrimp growth productivity.

Effect of lignite fulvic acid on growth, antioxidant ability, and HSP70 of Pacific white shrimp, Litopenaeus vannamei

This study was conducted to evaluate the effects of fulvic acid (0, 0.3, 0.6, 0.9, and 1.2%) as feed additive on growth, feed utilization, antioxidant ability, and HSP70 in hemolymph and hepatopancreas of juvenile white shrimp Litopenaeus vannamei (average weight 2.5 g) reared under experiment conditions. Shrimp were stocked at a density of 625 shrimps m−3 for 60 days in net cages submerged in recirculating tanks. At the end of the experiment, specific growth rates and survival rates of shrimp in treatment groups fed with 0.6, 0.9, and 1.2% fulvic acid were higher compared to that of the control group. Shrimp fed 0.6, 0.9, and 1.2% fulvic acid had significantly lower feed conversion rates than those fed control diet. The optimum dietary fulvic acid requirement for juvenile shrimp based on weight gain was 0.897%. Furthermore, superoxide dismutase activity and peroxidase activity increased significantly, while malonaldehyde content decreased in the hemolymph and hepatopancreas of shrimp fed 0.9 and 1.2% dietary fulvic acid. Glutathione content increased obviously in hemolymph of shrimp fed 0.6, 0.9, and 1.2% fulvic acid. In hepatopancreas, glutathione content was significantly higher in shrimp supplemented with 1.2% fulvic acid. HSP70 decreased obviously in hemolymph of shrimp fed 0.9 and 1.2% fulvic acid, while shrimp fed with 0.6 and 0.9% fulvic acid showed lower HSP70 level in hepatopancreas. The results of this study demonstrated that dietary fulvic acid could improve survival rates, growth, feed utilization, antioxidant capability, and stress resistance of juvenile L. vannamei reared under intensive stocking conditions.

Acute toxicity of carbon dioxide to juvenile marine shrimp Litopenaeus vannamei (Boone 1931)

ABSTRACTElevated concentrations of dissolved carbon dioxide (CO2) and reduced pH levels are observed during the culture and transportation of aquatic organisms. Studies on the toxicity effects of CO2 in penaeid shrimp are scarce when compared to the amount of research in fish. The objective of the present study was to determine the lethal concentration and safety levels of CO2 for juvenile white shrimp Litopenaeus vannamei. Juveniles (1.76 ± 0.36 g) were exposed for 96 h to one of six concentrations of dissolved CO2 (14.5, 23.8, 59.0, 88.0, 115.0, and 175.0 mg/L) or a control condition (without the addition of CO2), and their survival was monitored for 96 h. The LC50 values with 95% confidence limits at 24, 48, 72, and 96 h were 130.05 (104.2–162.1), 77.2 (73.8–80.02), 69.65 (65.47–74.32), and 59.12 (53.08–66.07) mg/L of CO2, respectively. The calculated safety level was 5.9 mg/L of CO2, and the highest concentration that did not induce significantly higher mortality than that observed in controls (NOEC) was 23.8 mg/L of CO2. We recommend that CO2 levels should be kept below the safety level obtained in this study.

Effect of silver nanoparticles on the metabolic rate, hematological response, and survival of juvenile white shrimp Litopenaeus vannamei

White spot syndrome virus (WSSV) is highly lethal and contagious in shrimps; its outbreaks causes an economic crisis for aquaculture. Several attempts have been made to treat this disease; however, to date, there is no effective cure. Because of their antimicrobial activities, silver nanoparticles (AgNPs) are the most studied nanomaterial. Although the antiviral properties of AgNPs have been studied, their antiviral effect against viral infection in aquaculture has not been reported. The AgNPs tested herein are coated with polyvinylpyrrolidone (PVP) and possess multiple international certifications for their use in veterinary and human applications.The aim of this work was to evaluate the survival rate of juvenile white shrimps (Litopenaeus vannamei) after the intramuscular administration of AgNPs. For this, different concentrations of metallic AgNPs and PVP alone were injected into the organisms. After 96 h of administration, shrimp survival was more than 90% for all treatments. The oxygen consumption routine rate and total hemocyte count remained unaltered after AgNP injection, reflecting no stress caused. We evaluated whether AgNPs had an antiviral effect in shrimps infected with WSSV. The results revealed that the survival rate of WSSV-infected shrimps after AgNP administration was 80%, whereas the survival rate of untreated organisms was only 10% 96 h after infection. These results open up the possibility to explore the potential use of AgNPs as antiviral agents for the treatment of diseases in aquaculture organisms, particularly the WSSV in shrimp culture.

Apparent digestibility of protein, energy and amino acids of six protein sources included at three levels in diets for juvenile white shrimp Litopenaeus vannamei reared in high performance conditions

The apparent digestibility coefficients (ADC) of six practical protein ingredients, Chilean fish meal (FM), soy protein concentrate (SPC), poultry by-product meal (PBM), corn gluten meal (CGM), meat and bone meal (MBM), and hydrolyzed feather meal (HFM), were determined for juvenile white shrimp (Litopenaeus vannamei) at dietary inclusion levels of 10, 20 and 30% within a reference diet containing 20% fish meal. The shrimp was stocked in 500L tanks equipped with automatic feeders and settling columns for solids collection in a recirculating system. The highest growth rates were observed for the shrimp fed with the test diets with FM and SPC, from the 30% to 10% inclusion levels, followed by the byproducts HFM, MBM, PBM and CGM, from the 10% to 30% inclusion levels. The effects of the protein sources and inclusion levels on the apparent digestibility coefficients of ingredients were more pronounced than in the test diets. The calculated ADC of the test ingredients were significantly affected by the ingredient type and inclusion level, with the exception for the protein ADC. The highest apparent digestibility coefficients of the ingredients were recorded for FM, SPC, PBM and MBM at the 20% inclusion level and CGM at the 30% inclusion level. The apparent amino acid digestibility (AAAD) recorded for the ingredients were different from previously reported values for the L. vannamei. The in vivo method for digestibility determination is subjected to different factors affecting its accuracy. Further studies should aim to improve the precision and produce reliable data to support feed formulation, nutrient assimilation, and aquatic animal performance.Statement of relevanceKnowledge about the nutritional value of ingredients for shrimp diets is needed. This paper introduces new information about the digestibility of commercial feedstuffs given at different levels, in a practical diet. Shrimp were reared in a RAS using specifically designed tanks, with performance comparable to shrimp farms. Effects of the method on the reliability of digestibility data are also discussed.

Homeopathy for shrimp aquaculture: increased survival and superoxide dismutase activity in juvenile white shrimp Litopenaeus vannamei during a bacterial pathogen-challenge

Homeopathy for shrimp aquaculture: increased survival and superoxide dismutase activity in juvenile white shrimp Litopenaeus vannamei during a bacterial pathogen-challenge

Heritability of body weight and resistance to ammonia in the Pacific white shrimp Litopenaeus vannamei juveniles

Ammonia, toxic to aquaculture organisms, represents a potential problem in aquaculture systems, and the situation is exacerbated in closed and intensive shrimp farming operations, expecially for Litopenaeus vannamei. Assessing the potential for the genetic improvement of resistance to ammonia in L. vannamei requires knowledge of the genetic parameters of this trait. The heritability of resistance to ammonia was estimated using two descriptors in the present study: the survival time (ST) and the survival status at half lethal time (SS50) for each individual under high ammonia challenge. The heritability of ST and SS50 were low (0.154 4±0.044 6 and 0.147 5±0.040 0, respectively), but they were both significantly different from zero (P 0.05), suggesting that ST and SS50 could be used as suitable indicators for resistance to ammonia. There were also positive phenotypic and genetic correlation between resistance to ammonia and body weight, which means that resistance to ammonia can be enhanced by the improvement of husbandry practices that increase the body weight. The results from the present study suggest that the selection for higher body weight does not have any negative consequences for resistance to ammonia. In addition to quantitative genetics, tools from molecular genetics can be applied to selective breeding programs to improve the efficiency of selection for traits with low heritability.

The detoxification process, bioaccumulation and damage effect in juvenile white shrimp Litopenaeus vannamei exposed to chrysene

This study aimed to evaluate the effect of chrysene (CHR) on detoxification enzymes, bioaccumulation and effect of CHR on biomolecule damage in different organs of the juvenile white shrimp Litopenaeus vannamei. In this study, juvenile white shrimp L. vannamei were exposed to CHR for 21 days at four different concentrations as 0, 0.3, 2.1 and 14.7μg/L. Results showed that CHR bioaccumulation increased rapidly at first then reached a plateau. The activities of aryl hydrocarbon hydroxylase (AHH), 7-ethoxyresorufin O-deethylase (EROD), epoxide hydrolase (EH), glutathione-S-transferase (GST), sulfotransferase (SULT) and uridinediphosphate glucuronyltransferase (UGT) were induced and then became stable gradually. Moreover, 2.1 and 14.7μg/L CHR treatments increased activity of superoxide dismutase (SOD) in gills and hepatopancreas, while total antioxidant capacity (T-AOC) and GSH/GSSG were suppressed after CHR exposure. Additionally, lipid peroxidation (LPO) levels, protein carbonyl (PC) contents and DNA damage were induced throughout the exposure period, and different trends were detected with time of exposure. Overall, these novel findings of CHR bioaccumulation and resulted toxicity demonstrate that CHR could affect the physical status of L. vannamei. This study will form a solid basis for a realistic extrapolation scientific data for aquaculture water monitoring and food security.

Growth and Lipid Metabolism of the Pacific White ShrimpLitopenaeus vannameiat Different Salinities

Juvenile white shrimp Litopenaeus vannamei (1.98 ± 0.28 g) were fed a commercial diet for 8 wk in triplicate to investigate growth and lipid metabolism at 3 salinities (3, 17, and 30). Shrimp weight gain and survival at 3 were significantly less than that at 17 and 30. No differences were found in whole-body proximate composition. Linolenic acid (18:3[n-3]) and (n-3) long-chain unsaturated fatty acid levels in the hepatopancreas, and n-3 long-chain polyunsaturated fatty acid level, especially eicosapentaenoic acid (EPA; C20:5[n-3]) and docosahexaenoic acid (DHA; C22:6[n-3]) in muscle at 3 were significantly greater than at other salinities. Fatty acid synthase, hormone sensitive lipase, lipoprotein lipase, adipose triacylglycerol lipase, acyl-CoA, diacylglycerol acyltransferase 2, elongase of very long-chain fatty acid 6, and Δ5 and Δ6 fatty acid desaturase activity was detected and showed a negative trend with an increase of salinity, and no significant differences were found among salinity groups (P > 0.05). The results indicate that the low salinity of 3 decreases the growth of L. vannamei. Although L. vannamei could not synthesize either DHA or EPA de novo, it possibly has the potential ability to convert linolenic acid to DHA and EPA regardless of salinity. However, the factors influencing this ability remain unknown and need further study.

Growth, Body Composition, and Ammonia Tolerance of Juvenile White ShrimpLitopenaeus vannameiFed Diets Containing Different Carbohydrate Levels at Low Salinity

Effects of dietary carbohydrate (CBH) levels on growth, body composition, and ammonia tolerance of juvenile white shrimp Litopenaeus vannamei at a low salinity of three were evaluated. Six isonitrogenous and isolipid diets containing different CBH levels were formulated and fed to juvenile L. vannamei for 42 days in triplicate for each treatment. Weight gain and survival rate of shrimp fed 20% CBH were the greatest and differed from those fed 5% CBH and 30% CBH. Shrimp whole-body crude protein of the 20% CBH group was significantly greater than that of other treatments. Whole-body crude lipid levels increased with the increase of dietary CBH, and was significantly higher in the 20%, 25%, and 30% CBH groups than in the control. Hepatosomatic index, condition factor, whole-body moisture, and ash contents were not affected by dietary CBH levels. Hepatopancreas soluble protein peaked in shrimp fed 20% CBH, and was significantly greater than in other groups. Hepatopancreas and muscle glycogen showed a similar tendency, but peaked in shrimp fed 15% CBH. Malate dehydrogenase, pyruvate kinase, and glucose-6-phosphate dehydrogenase activities were not affected significantly by dietary CBH levels. An ammonia challenge of 96 h showed that the shrimp in the 20% CBH group had the greatest survival rate, although no significant differences were observed among treatments. This study indicates that 15%–20% dietary CBH is optimal for growth and can improve the ability of L. vannamei to handle stress at low salinities.

Growth, Body Composition, and Ammonia Tolerance of Juvenile White ShrimpLitopenaeus vannameiFed Diets Containing Different Carbohydrate Levels at Low Salinity

Effects of dietary carbohydrate (CBH) levels on growth, body composition, and ammonia tolerance of juvenile white shrimp Litopenaeus vannamei at a low salinity of three were evaluated. Six isonitrogenous and isolipid diets containing different CBH levels were formulated and fed to juvenile L. vannamei for 42 days in triplicate for each treatment. Weight gain and survival rate of shrimp fed 20% CBH were the greatest and differed from those fed 5% CBH and 30% CBH. Shrimp whole-body crude protein of the 20% CBH group was significantly greater than that of other treatments. Whole-body crude lipid levels increased with the increase of dietary CBH, and was significantly higher in the 20%, 25%, and 30% CBH groups than in the control. Hepatosomatic index, condition factor, whole-body moisture, and ash contents were not affected by dietary CBH levels. Hepatopancreas soluble protein peaked in shrimp fed 20% CBH, and was significantly greater than in other groups. Hepatopancreas and muscle glycogen showed a similar tendency, but peaked in shrimp fed 15% CBH. Malate dehydrogenase, pyruvate kinase, and glucose-6-phosphate dehydrogenase activities were not affected significantly by dietary CBH levels. An ammonia challenge of 96 h showed that the shrimp in the 20% CBH group had the greatest survival rate, although no significant differences were observed among treatments. This study indicates that 15%–20% dietary CBH is optimal for growth and can improve the ability of L. vannamei to handle stress at low salinities.

Immunotoxic effect of Benzo[α]Pyrene and chrysene in juvenile white shrimp Litopenaeus vannamei

Abstract The effects of benzo(a)pyrene (Bap) (0.03, 0.3 and 3 μg L−1) and chrysene (CHR) (0.3, 2.1 and 14.7 μg L−1) on the function of the immune system of juvenile white shrimp Litopenaeus vannamei were determined under laboratory conditions. This included the total hemocyte count (THC) in the hemolymph, phagocytic activityand pro-phenoloxidase (pro-PO) activity of the hemocyte, phenoloxidase (PO) activity, α2-macroglobulin (α2-M) activity, bacteriolytic activity and antibacterial activity in the hemolymph. The results showed that BaP and CHR could inhibit the immune function of L. vannamei significantly under high concentration BaP and CHR exposure. The results of this study indicated that the immunotoxicity of PAHs in a descending order was BaP&gt;CHR. Moreover, the results indicated the THC in hemolymph, pro-PO activity and phagocytic activity of hemocyte, and bacteriolytic activity in hemolymphcould be used as potentially suitable biomarkersfor early warning indication of PAHs toxicity, this could provide useful information for toxic risk assessment of environmental pollutants.