Pacific White Shrimp Litopenaeus Vannamei Research Articles

Effects of Tannin Supplementation in Diet on the Resistance to Ammonia Stress of Pacific White Shrimp Litopenaeus vannamei

Tannin (TA), as a natural phenolic compound with strong antioxidant activity, has been used as a feed additive for various animals. In this study, we fed a diet containing 800 mg/kg of tannin on Litopenaeus vannamei for 56 days and then subjected to acute ammonia stress for 48 hr to investigate the effect of dietary tannin on the ammonia stress response of L. vannamei through transcriptomic and metabolomic analysis. The transcriptome analysis indicated that ammonia stress-induced differential expression of 4,185 genes, while tannin-fed shrimp only had 964 differentially expressed genes. Compared with the TA_0 group, 59 pathways were significantly altered, and the pathways of “starch and sucrose metabolism,” “retinol metabolism,” “arachidonic acid metabolism,” “lysosome,” and “amino sugar and nucleotide sugar metabolism” were highly enriched in the TS_0 group. Compared with the TS_0 group, six pathways were significantly altered, and the pathways of “dilated cardiomyopathy,” “complement and coagulation cascades,” “cardiac muscle contraction,” “fructose and mannose metabolism,” “cGMP-PKG signaling pathway,” and “beta-alanine metabolism” were significantly enriched in the TS_800 group. Metabolomic analysis showed that a total of 107 differential metabolites (DMs) were identified in the TS_0 vs. TA_0 group, while 75 DMs were identified in the TS_800 vs. TS_0 group. Based on KEGG annotation, it was found that a large amount of DM was significantly enriched in amino acid metabolism pathways in the TS_0 group, including “arginine and proline metabolism,” “alanine, aspartic acid, and glutamic acid metabolism,” “β-Alanine metabolism and tyrosine metabolism” indicated that tannins affect the metabolism of amino acids. The integration of DEGs and DMs indicates that dietary tannins highly alter the digestion and absorption functions of proteins, as well as the biosynthesis and metabolism of amino acids. This study provides new insights into the adaptation of Pacific white shrimp to ammonia stress and the addition of tannins to feed to enhance immune function.

Gene structure, expression and function analysis of the MyoD gene in the Pacific white shrimp Litopenaeus vannamei

The Pacific white shrimp Litopenaeus vannamei is a representative species of decapod crustacean and an economically important marine aquaculture species worldwide. However, research on the genes involved in muscle growth and development in shrimp is still lacking. MyoD is recognized as a crucial regulator of myogenesis and plays an essential role in muscle growth and differentiation in various animals. Nonetheless, little information is available concerning the function of this gene among crustaceans. In this study, we identified a sequence of the MyoD gene (LvMyoD) with a conserved bHLH domain in the L. vannamei genome. Phylogenetic analysis revealed that both the overall protein sequence and specific functional sites of LvMyoD are highly conserved with those of other crustacean species and that they are evolutionarily closely related to vertebrate MyoD and Myf5. LvMyoD expression is initially high during early muscle development in shrimp and gradually decreases after 40 days post-larval development. In adults, the muscle-specific expression of LvMyoD was confirmed through RT–qPCR analysis. Knockdown of LvMyoD inhibited the growth of the shrimp in body length and weight. Histological observation and transcriptome sequencing of muscle samples after RNA interference (RNAi) revealed nuclear agglutination and looseness in muscle fibers. Additionally, we observed significant effects on the expression of genes involved in heat shock proteins, myosins, actins, protein synthesis, and glucose metabolism. These findings suggest that LvMyoD plays a critical role in regulating muscle protein synthesis and muscle cell differentiation. Overall, this study highlights the involvement of LvMyoD in myogenesis and muscle growth, suggesting that it is a potentially important regulatory target for shrimp breeding efforts.

Comparative transcriptome analysis provides a glance into the regulatory of insulin-like peptide 1 gene in the Pacific white shrimp Litopenaeus vannamei

Insulin-like peptides (ILPs) have been reported to exert significant and diverse regulatory effects through the insulin signaling pathway in invertebrates. However, there is a large research gap in the functional analysis of ILP genes in crustaceans. In this study, we combined RNA interference (RNAi) technology with transcriptome sequencing to investigate the regulatory effects of the ILP1 gene in the Pacific white shrimp Litopenaeus vannamei. After two weeks of continuous RNAi of LvILP1, the shrimp in the dsLvILP1 group exhibited reduced body length gain, weight gain, molting rate, and hemolymph glucose concentration compared to the control dsEGFP group, indicating that knockdown of LvILP1 slowed shrimp growth, molting, and metabolism. Comparative transcriptome analysis of three tissues revealed that knockdown of LvILP1 inhibited muscle growth and development by modulating the mTOR and MAPK signaling pathways, and prevented the renewal of epidermal tissue through the Hippo signaling pathway. Meanwhile, it also suppressed certain growth signals in the hepatopancreas, such as juvenile hormone (JH) synthesis and 20-hydroxyecdysteroid (20E) signal activation. Additionally, it promoted the conversion pathway of some sugars into amino acid metabolism instead of energy metabolism after glycolysis in the hepatopancreas. Interestingly, knockdown of LvILP1 also affected carbohydrate metabolism by regulating the intracellular and extracellular transport of glucose and trehalose, as well as regulating the expression levels of key metabolic genes in three shrimp tissues. This disruption led to a decrease in blood glucose levels and suppressed energy production, ultimately providing less energy for shrimp growth and molting. This study provides valuable insights into the underlying genetic mechanism through which ILP1 regulates glucose metabolism and growth in shrimp. It enhances our understanding of the structure and function of the insulin pathway in crustaceans and serves as an important reference for the identification of candidate genes in molecular genetic breeding of shrimp.

Dietary Lysophosphatidylcholine Improves the Uptake of Astaxanthin and Modulates Cholesterol Transport in Pacific White Shrimp Litopenaeus vannamei.

Astaxanthin (AST), functioning as an efficient antioxidant and pigment, is one of the most expensive additives in shrimp feeds. How to improve the uptake efficiency of dietary astaxanthin into farmed shrimp is of significance. The present study investigated the effects of lysophosphatidylcholine (LPC), an emulsifier, on dietary astaxanthin efficiency, growth performance, body color, body composition, as well as lipid metabolism of juvenile Pacific white shrimp (average initial body weight: 2.4 g). Three diets were prepared: control group, the AST group (supplemented with 0.02% AST), and the AST + LPC group (supplemented with 0.02% AST and 0.1% LPC). Each diet was fed to triplicate tanks, and each tank was stocked with 30 shrimp. The shrimp were fed four times daily for eight weeks. The AST supplementation improved the growth of white shrimp, while LPC further promoted the final weight of shrimp, but the whole-shrimp proximate composition and fatty acid composition were only slightly affected by AST and LPC. The LPC supplementation significantly increased the astaxanthin deposition in the muscle. The LPC supplementation significantly increased the shell yellowness of both raw and cooked shrimp compared to the AST group. Moreover, the dietary LPC increased the high-density lipoprotein-cholesterol content but decreased the low-density lipoprotein-cholesterol content in the serum, indicating the possible regulation of lipid and cholesterol transport. The addition of astaxanthin significantly up-regulated the expression of npc2 in the hepatopancreas compared to the control group, while the addition of LPC down-regulated the expression of mttp compared to the AST group. In conclusion, the LPC supplementation could facilitate the deposition of dietary astaxanthin into farmed shrimp and further enlarge the beneficial effects of dietary astaxanthin. LPC may also independently regulate shrimp body color and cholesterol transportation. This was the first investigation of the promoting effects of LPC on dietary astaxanthin efficiency.

Identification of Growth-Related Gene BAMBI and Analysis of Gene Structure and Function in the Pacific White Shrimp Litopenaeus vannamei.

As one of the most important aquaculture species in the world, the improvement of growth traits of the Pacific white shrimp (Litopenaeus vannamei), has always been a primary focus. In this study, we conducted SNP-specific locus analysis and identified a growth-related gene, BAMBI, in L. vannamei. We analyzed the structure and function of LvBAMBI using genomic, transcriptomic, metabolomic, and RNA interference (RNAi) assays. The LvBAMBI possessed highly conserved structural domains and widely expressed in various tissues. Knockdown of LvBAMBI significantly inhibited the gain of body length and weight of the shrimp, underscoring its role as a growth-promoting factor. Specifically, knockdown of LvBAMBI resulted in a significant downregulation of genes involved in lipid metabolism, protein synthesis, catabolism and transport, and immunity. Conversely, genes related to glucose metabolism exhibited significant upregulations. Analysis of differential metabolites (DMs) in metabolomics further revealed that LvBAMBI knockdown may primarily affect shrimp growth by regulating biological processes related to lipid and glucose metabolism. These results suggested that LvBAMBI plays a crucial role in regulating lipid metabolism, glucose metabolism, and protein transport in shrimp. This study provides valuable insights for future research and utilization of BAMBI genes in shrimp and crustaceans.

Toll-like receptor expression in Pacific white shrimp (Litopenaeus vannamei) reveals differential responses after fungal (Fusarium solani) infection

Toll-like receptor expression in Pacific white shrimp (Litopenaeus vannamei) reveals differential responses after fungal (Fusarium solani) infection

Shelf-life extension of Pacific white shrimp (Litopenaeus vannamei) using sodium alginate/chitosan incorporated with cell-free supernatant of Streptococcus thermophilus FUA 329 during cold storage.

Seafood is highly perishable and has a short shelf-life. This study investigated the effect of chitosan and alginate (CH-SA) coating combined with the cell-free supernatant of Streptococcus thermophilus FUA329 (CFS) as a preservative on the quailty of white shrimp (Litopenaeus vannamei) refrigerated at 4° for 0, 3, 6, 9, 12, 15 days. Freshly shrimps were randomly divided into four groups: the CFS group (400 mL); the CH-SA group (1% chitosan/1% alginate); the CFS-CH-SA group (1% chitosan/1% alginate with 400 mL CFS) are treatment groups, and the control group (400 mL sterile water). The CFS-CH-SA coating effectively suppressed microbial growth total viable count and chemical accumulation (pH, total volatile basic nitrogen, thiobarbituric acid reactive substance) compared with the control. Additionally, the CFS-CH-SA coating improved the texture and sensory characteristics of shrimp during storage. The coated shrimp exhibited significantly reduced water loss (p<0.05). The combination of CH-SA coating with CFS treatment can extend the shelf life of shrimp. PRACTICAL APPLICATION: Recently, edible films have received more consideration as a promising method to enhance the shelf life of seafood. The presence of Lactic acid bacteria metabolites in edible films reduces spoilage and improves consumer health. Our findings encourage the application of edible coating incorporated with cell-free supernatant of Streptococcus thermophilus FUA 329 to design multifubctional foods and preserve the qualities of shrimp.

Effect of dietary phytase and protease supplementation on the growth performance and apparent nutrient digestibility in juvenile Pacific white shrimp (Litopenaeus vannamei) fed fish meal–free and phosphorus limiting diets

Effect of dietary phytase and protease supplementation on the growth performance and apparent nutrient digestibility in juvenile Pacific white shrimp (Litopenaeus vannamei) fed fish meal–free and phosphorus limiting diets

Acute stress response in gill of Pacific white shrimp Litopenaeus vannamei to high alkalinity

As a multifunctional organ, the gill plays a key role in the regulation of homeostasis. Excessive alkalinity in water can seriously threaten the survival of aquatic animals, however, the studies on the mechanism of alkalinity stress and adaption of crustacea are still limited. In this study, we aimed to investigate the mechanisms of acute alkalinity stress in the gill of Pacific white shrimp Litopenaeus vannamei by integrating physiological, histological, transcriptome, and metabolome analyses, which is an important aquaculture species of crustaceans. The physiological parameters related to homeostasis regulation, oxidative stress, material metabolism, and ammonia detoxification were significantly changed under acute alkalinity stress. There were a considerable number of genes and metabolites that were significantly changed in expression and level, which related to glycolysis/gluconeogenesis, fatty acid metabolism, amino acid metabolism, antioxidation, ammonia metabolism, and glycerophospholipid metabolism, In addition, the local structure of the gill was damaged and accompanied by cell apoptosis. The above results indicate that acute alkalinity stress can lead to damage to the gill structure, and affect its ion transport function, and the genes related to ion transport protein were upregulated. The antioxidant capacity in the gill was strengthened under acute alkalinity stress, at the same time, acute alkalinity stress would induce apoptosis in the gill. The glycogen catabolism in gill was significantly enhanced under acute alkalinity stress, while the lipid anabolism was inhibited, and the mechanism of the ornithine-urea cycle has been further mobilized to alleviate the inhibition of ammonia excretion and the accumulation of metabolic ammonia in the internal environment. In addition, the glycerophospholipid metabolism in the gill was disturbed under acute alkalinity stress. The current study will provide important clues for understanding the alkalinity stress mechanism of crustaceans, and provide an important theoretical basis for the optimization of shrimp aquaculture in saline-alkaline waters.

Salt type, sugar addition, and system type in intensive RAS for Pacific white shrimp (Litopenaeus vannamei) production

The use of a low-cost, homemade salt mixture in hybrid RAS may reduce operational costs for inland marine aquaculture producers. The addition of sugar in RAS may benefit shrimp growth by making suspended microbes richer in protein, which shrimp can then consume. Increased digestive enzyme activity has been noted in shrimp raised in systems with a substantial abundance of biofloc particles. However, there is still debate over whether clear-water RAS may be superior to particulate-rich systems. This study examined the effects of system type, low-cost salt, and sugar addition on the production, water quality, and digestive enzyme activity of L. vannamei. In the study, two levels of each experimental factor were used. The factors used were system type (clear water-CW vs hybrid-HY), salt type (Least Cost-L vs Commercial-C), and sugar (presence or absence of sugar addition: S vs. N). There was a total of eight treatments: HY-L-S, HY-L-N, HY-C-S, HY-C-N, CW-L-S, CW-L-N, CW-C-S, and CW-C-N, each of which had three randomly assigned, replicate, 1 m3 tanks. All tanks were stocked with 250 shrimp per m3 (3.1 g average weight), extra filtration was used in CW tanks, and sugar (sucrose) was added at a targeted C:N ratio of 14:1 in the sugar tanks. At the end of the experiment, the hepatopancreas was removed from shrimp for digestive enzyme analyses. Results from the experiment showed no significant differences in the average weight, total harvest, FCR, and growth rate between system types and salt types. However, the use of sugar resulted in significantly reduced mean individual weight of shrimp. Nitrate concentration was significantly lower and solids concentrations were higher in the tanks receiving sugar compared to those with no sugar addition. There were no significant differences in amylase activity between treatments, but trypsin activity was higher in the HY systems than the CW systems. The results of this study indicate that this particular low-cost salt mixture had no adverse effects on the water quality, production, or enzyme metrics tested. Biofloc particles seem to have enhanced trypsin activity in the HY system shrimp. Lastly, the addition of sugar had some substantial impacts on solids and nitrate concentrations, as well as negative effects on shrimp growth. Both independently and in combination, the factors examined in this project may have important implications for the management of intensive shrimp aquaculture operations.

Impact of the co-cultivation of macroalgae (Ulva lactuca f. fasciata) on the composition of biofloc in a zero water exchange system used for rearing Pacific white shrimp (Litopenaeus vannamei) (Decapoda, Dendrobranchiata)

Abstract In a closed, or zero water exchange, greenhouse aquaculture system, this study examined the interaction between the aggregation flocs in the mono- and co-cultivation of Pasific white shrimp, Litopenaeus vannamei (300 individuals/m3) with macroalgae, Ulva lactuca f. fasciata at different densities of Ulva (1, 2 and 3 g/l). The investigation was conducted under zero water exchange conditions. The accumulated flocs were compared between the various treatment groups: without Ulva (Treatment Control Group), Ulva at 1 g/l density (T1: Treatment 1), Ulva at 2 g/l (T2: Treatment 2), and Ulva at 3 g/l (T3: Treatment 3). Ultimately, it was determined that Ulva cultivation using the Biofloc system actually helped to ensure the water quality in the zero water exchange culture system during the 35-day experimental period with reduced cyanophyte densities, that can cause toxic algal blooms in aquaculture systems. This was interpreted to result from the fact that Ulva is a naturally occurring bioremediation agent.

The interactions between CpG oligodeoxynucleotides and Toll-like receptors in Pacific white shrimp Litopenaeus vannamei

CpG oligodeoxynucleotides (ODNs), as a novel type of adjuvant with immunomodulatory effects, are recognized by Toll-like receptors (TLRs) in Litopenaeus vannamei. In the present study, eleven LvTLRs-pCMV recombinants (rLvTLRs) were constructed to investigate the relationships between various CpG ODNs and different LvTLRs in human embryonic kidney 293T (HEK293T) cells, which was further confirmed by bio-layer interferometry (BLI) technique. The results of dual luciferase reporter assay showed that every LvTLR could activate multiple downstream genes, mainly including NF-κB, CREB, ISRE, IL-6-promoter, TNF-α-promoter and Myc, thereby inducing main signaling pathways in shrimps. Most CpG ODNs possessed affinities to more than one LvTLR, while each LvTLR could recognize multiple CpG ODNs, and the widely recognized ligands within CpG ODNs are A-class and B-class. Moreover, BLI analysis showed that CpG 2216, Cpg 2006, CpG 2143 and CpG 21425 exhibited dose-dependent affinity to the expressed TLR protein, which were consistent with the results in HEK293T cells. It suggested that the interactions of CpG ODNs with LvTLRs were indispensable for the immune regulation triggered by CpG ODNs, and these findings would lay foundations for studying the activations of LvTLRs to immune signaling pathways and shedding lights on the immune functions and mechanisms of CpG ODNs.

Effects of myo-inositol on growth and biomarkers of environmental stress and metabolic regulation in Pacific white shrimp (Litopenaeus vannamei) reared at low salinity

This study explored the role of myo-inositol in alleviating the low salinity stress of White Shrimp (Litopenaeus vannamei). Juvenile shrimp (0.4 ± 0.02 g) in low salinity (salinity 3) water were fed diets with myo-inositol levels of 0, 272, 518, 1020 and 1950 mg/kg (crude protein is 36.82 %, crude lipid is 7.58 %), fed shrimp in seawater at a salinity of 25 were fed a 0 mg/kg myo-inositol diet as a control (Ctrl). The experiment was carried out in tanks (50 L) with satiety feeding, and the experiment lasted for 6 weeks. After sampling, the serum was used to measure immune function, the hepatopancreas homogenate was used to measure the antioxidant capacity and hepatopancreas damage state, the hepatopancreas was used for transcriptomics analysis, and the gills were used for qPCR to measure osmotic pressure regulation. The results showed that the final weight and survival of the shrimp in the 1020 mg/kg group increased significantly compared with those in the other low salinity groups, but the final weight and biomass increase were significantly lower than those in the Ctrl group. Dietary myo-inositol improved the antioxidant capacity of shrimp under low salinity. B-cell hyperplasia and hepatic duct damage were observed in the hepatopancreas in the 0 mg/kg group. The results of transcriptome analysis showed that myo-inositol could participate in the osmotic pressure regulation of shrimp by regulating carbohydrate metabolism, amino acid metabolism, lipid metabolism and other related genes. Myo-inositol significantly affected the expression of related genes in ion transporter and G protein-coupled receptor-mediated pathways. This study demonstrated that myo-inositol can not only act as an osmotic pressure effector and participate in the osmolar regulation of shrimp through the phosphatidylinositol signaling pathway mediated by G protein-coupled receptors but also relieve low salinity stress by mediating physiological pathways such as immunity, antioxidation, and metabolism in shrimp. The binomial regression analysis of biomass increases and survival showed that the appropriate amount of myo-inositol in the L. vannamei diet was 862.50–1275.00 mg/kg under low salinity.

Comparative Analysis of the Culture of Pink Shrimp Farfantepenaeus brasiliensis and Pacific White Shrimp Litopenaeus vannamei in Biofloc System

Shrimp farming in the Biofloc Technology System (BFT) is already considered an alternative to the traditional culture. The bioflocs maintain the water quality and can be used as a food supplement for shrimp. The Pacific white shrimp Litopenaeus vannamei forms the basis for most of the production in BFT. However, its culture is limited by the low temperatures. Thus, the BFT culture potential of native species, such as the pink shrimp Farfantepenaeus brasiliensis, should be considered. The present study aimed to compare the cultures of F. brasiliensis and L. vannamei in the grow-out phase in the BFT system. The experiment comprised two treatments: (FB), grown out of F. brasiliensis, and (LV), grown out of L. vannamei. The study lasted 70 days and was conducted at the Marine Station of Aquaculture at the Federal University of Rio Grande, Rio Grande do Sul State, Brazil. The stocking density was 100 shrimp/m² for both species. The shrimp were fed twice a day with commercial food. The physicochemical parameters of the water were monitored throughout the experimental period. The results showed that all physicochemical parameters of the water remained within the tolerated limits for both species. However, during the growth phase in the BFT, it was observed that the L. vannamei shrimp showed a better zootechnical performance than F. brasiliensis. The results indicate that L. vannamei has a higher capacity to catch bioflocs as supplementary food, demonstrating a better response of that species to the BFT system in the grow-out phase compared to F. brasiliensis.

Diversity of heat shock proteins in response to various stressors in the Pacific white shrimp Litopenaeus vannamei

Heat shock proteins (HSPs) serve as an evolutionarily conserved superfamily in response to various environmental stressors in almost all organisms. The Pacific white shrimp, Litopenaeus vannamei, is a worldwide aquaculture species, which have to face various environmental stressors during the whole aquaculture process. Landscapes of HSPs at genomic level will be helpful for understanding the mechanism of this species in environment adaptation. In this study, a comprehensive analysis on the composition and expression profile of HSPs have been performed in L. vannamei. A total of 76 HSP encoding genes (one LvHSP10s, four LvsHSPs, 38 LvHSP40s, ten LvHSP60s, 14 LvHSP70s, five LvHSP90s and four LvHSP100s) have been identified. Most of these genes are dispersedly distributed in the genome, except for seven pairs of tandemly duplicated genes. Multi-transcriptome analyses indicated that LvHSPs are sensitive to various stressors, including pathogen infection, salinity, ammonia or temperature stress. The LvHSP family exhibited obvious tissue specificity in response to various stressors. Additionally, we found that both tandem duplication and alternative splicing of LvHSPs contributed to the adaptation to various stresses. These findings will provide clues for stress adaptation and development of aquaculture management strategies in penaeid shrimp.

Structure and function analyses of the SRC gene in Pacific white shrimp Litopenaeus vannamei

SRC gene encodes scavenger receptor class C, a member of the scavenger receptor family, and has only been identified and investigated in invertebrates. Our previous studies have revealed that SRC is a novel candidate gene associated with body weight in Pacific white shrimp (Litopenaeus vannamei). In order to comprehend the underlying mechanism by which LvSRC affects shrimp growth, we analyzed the structure, phylogeny, expression profiles and RNA interference (RNAi) of this gene in L. vannamei. We found that LvSRC contains two CCP domains and one MAM domain, with the highest expression level in the heart and relatively low expression level in other tissues. Notably, LvSRC exhibited significantly higher expression levels in the fast-growing group among groups with different growth rates, suggesting its potential involvement as a gene contributing to the growth of L. vannamei. RNAi of LvSRC inhibited body length and body weight gain compared to the control groups. Moreover, through RNA-seq analysis, we identified 598 differentially expressed genes (DEGs), including genes associated with growth, immunity, protein processing and modification, signal transduction, lipid synthesis and metabolism. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed significant changes in the signaling pathways related to growth, lipid metabolism and immune response, suggesting that LvSRC exhibits the potential to participate in diverse physiological processes and immune regulation. These findings deepen our understanding of the structure and function of the SRC in shrimp and lay the foundation for further research into the regulatory mechanism of LvSRC. Additionally, they provide potential applications in shrimp genetics and breeding.

Assessing the Interactive Effects of High Salinity and Stocking Density on the Growth and Stress Physiology of the Pacific White Shrimp Litopenaeus vannamei

This study was conducted to evaluate the effects of high salinity combined with stocking density on Litopenaeus vannamei. Three salinity gradients, namely, 28 g/L, 36 g/L, and 44 g/L, and two stocking densities, namely, 300 and 600 shrimp/m3, were used to analyze the synergistic effect of high salinity and stocking density on the growth performance, digestibility, and energy budgets of L. vannamei. The experimental testing period lasted 45 days. The research results showed that a salinity level of 36 g/L was the most suitable salinity level for shrimp growth under both high and low stocking densities. The body weight, specific growth rate, and relative weight gain of the shrimp in the 36 g/L salinity group were significantly higher than those in the other two salinity groups under both high and low stocking densities. The high-density farming group with 600 shrimp/m3 exhibited a significant inhibition of shrimp growth compared to the low-density group under the same salinity conditions. The activities of amylase, lipase, and protease in the high-density-group shrimp gradually decreased with an increase in salinity, and the three digestive enzymes had the same overall effect of changing trends. This indicates that under high-density farming conditions, the increase in salinity is not conducive to the digestive function of shrimps. At the same time, the proportion of respiratory energy to feeding energy gradually decreased in the high-density group and with the increase in salinity. However, under the same salinity conditions, the higher the stocking density, the higher the energy consumed by respiration compared to the low-density group. In addition, the expression of the growth-related gene’s small nuclear ribonucleoprotein polypeptide G (SNRPG) under high stocking density was significantly lower than that in the low-density group at a salinity of 28 g/L, and ribosomal protein L7 (RPL7) expression was also significantly lower under high stocking density than that in the low-density group at a salinity of 44 g/L. The expression levels of molting-related genes retinoid X receptor (RXR), ecdysone receptor (ECR), and ecdysone-induced protein 75 (E75) were significantly higher in the 36 g/L salinity group compared with the other two salinity groups under high-stocking-density treatment. The findings indicate that the synergistic effects of salinity and stocking density have a significant impact on the growth of L. vannamei, and excessive salinity would inhibit its growth in the process of high-density culturing.

Defining desired genetic gains for Pacific white shrimp (Litopenaeus vannamei) breeding objective using participatory approaches.

The objective of this study was to define desired genetic gains from economically important traits of Pacific white shrimp (Litopenaeus vannamei) using participatory approaches. Two questionnaires were sent out to 100 Pacific white shrimp farmers in all five Iranian shrimp farming provinces. Questionnaire A (Q-A) includes management factors and farming environments. Moreover, in this questionnaire, farmers were asked to rank the fourth most important traits in shrimp among 10 economic traits in the list for genetic improvement. In questionnaire B (Q-B), priorities of the four traits with the highest value were obtained using pairwise comparison. The results showed that the four most important traits were white spot syndrome virus resistance (WSSV), growth rate before 4 months (GR), acute hepatopancreatic necrosis disease resistance (AHPND), and female total weight at ablation (FTW). Medians of the best individual preference values were WSSV (0.222), GR (0.173), AHPND (0.157), and FTW (0.053). Most disagreements were found between the social group preference values in the commercial products and water salinity categories. Desired genetic gains were 1.71%, 1.57%, 0.53% and 0.31% for GR, AHPND, WSSV and FTW, respectively. This study highlighted that despite environmental and management differences, participatory approaches can achieve desired genetic results for Pacific white shrimp breeding programme.

Implications of dietary phosphorus sources on zootechnical performance and stress response of the pacific white shrimp Litopenaeus vannamei

The phosphorous (P) is an essential element for several functions, including the synthesis of high energy compounds in cells like adenosine triphosphate (ATP) and arginine phosphate (ArgP). The dietary requirements of P could change according to physiological and environmental conditions, particularly if organisms are exposed to stress conditions. As the P availability could be related to its chemical form in the diet, the present study analyzed the influence of different P sources (KH2PO4, NaH2PO4, NH4H2PO4, Na5P3O10), on the stress response of the Pacific white shrimp Litopenaeus vannamei. Final weight was 8.5% higher (p < 0.01) in shrimp fed on tripolyphosphate (Na5P3O10) diet compared with the monophosphate diets. Weight gain and specific growth also trend to increase, whereas feed conversion ratio trend to decrease with this polyphosphate source, although not significantly. Stress response of shrimp exposed to handling followed by hypoxia was characterized by an overall increase of lactate and glucose levels in hemolymph, as well as a decrease in Adenylate Energy Charge (AEC) and ArgP in the muscle. No effect of dietary P sources was observed on baseline biochemical composition and overall indicators of stress response, except for higher carbohydrate levels in hepatopancreas and RNAm expression of arginine kinase (AK) in muscle with the NaH2PO4 diet, suggesting a potentially better energy status with this diet.

Antibiotic Resistance and Genetic Profiles of Vibrio parahaemolyticus Isolated from Farmed Pacific White Shrimp (Litopenaeus vannamei) in Ningde Regions.

To better understand the antibiotic resistance, virulence genes, and some related drug-resistance genes of Vibrio parahaemolyticus in farmed pacific white shrimp (Litopenaeus vannamei) in Ningde regions, Fujian province, we collected and isolated a total of 102 strains of V. parahaemolyticus from farmed pacific white shrimp in three different areas of Ningde in 2022. The Kirby-Bauer disk method was used to detect V. parahaemolyticus resistance to 22 antibiotics, and resistant genes (such as quinolones (qnrVC136, qnrVC457, qnrA), tetracyclines (tet A, tetM, tetB), sulfonamides (sulI, sulII, sulIII), aminoglycosides (strA, strB), phenicols (cat, optrA, floR, cfr), β-lactams (carB), and macrolides (erm)) were detected by using PCR. The findings in this study revealed that V. parahaemolyticus was most resistant to sulfamoxazole, rifampicin, and erythromycin, with resistance rates of 56.9%, 36.3%, and 33.3%, respectively. Flufenicol, chloramphenicol, and ofloxacin susceptibility rates were 97.1%, 94.1%, and 92.2%, respectively. In all, 46% of the bacteria tested positive for multi-drug resistance. The virulence gene test revealed that all bacteria lacked the tdh and trh genes. Furthermore, 91.84% and 52.04% of the isolates were largely mediated by cat and sulII, respectively, with less than 5% resistance to aminoglycosides and macrolides. There was a clear mismatch between the antimicrobial resistance phenotypes and genotypes, indicating the complexities of V. parahaemolyticus resistance.