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Salinization of freshwater ecosystems is a pressing global issue. Changes in salinity can exert severe pressure on aquatic animals and jeopardize their survival. Procambarus clarkii is a valuable freshwater aquaculture species that exhibits some degree of salinity tolerance, making it an excellent research model for freshwater aquaculture species facing salinity stress. In the present study, crayfish were exposed to acute low salt (6 ppt) and high salt (18 ppt) conditions. The organisms were continuously monitored at 6, 24, and 72 h using RNA-Seq to investigate the mechanisms of salt stress resistance. Transcriptome analysis revealed that the crayfish responded to salinity stress with numerous differentially expressed genes, and most of different expression genes was observed in high salinity group for 24h. GO and KEGG enrichment analyses indicated that metabolic pathways were the primary response pathways in crayfish under salinity stress. This suggests that crayfish may use metabolic pathways to compensate for energy loss caused by osmotic stress. Furthermore, gene expression analysis revealed the differential expression of immune and antioxidant-related pathway genes under salinity stress, implying that salinity stress induces immune disorders in crayfish. More genes related to cell proliferation, differentiation, and apoptosis, such as the Foxo, Wnt, Hippo, and Notch signaling pathways, responded to high-salinity stress. This suggests that regulating the cellular replication cycle and accelerating apoptosis may be necessary for crayfish to cope with high-salinity stress. Additionally, we identified 36 solute carrier family (SLC) genes related to ion transport, depicting possible ion exchange mechanisms in crayfish under salinity stress. These findings aimed to establish a foundation for understanding crustacean responses to salinity stress and their osmoregulatory mechanisms.

Background: Salinity is one of the main influencing factors in the culture environment and is extremely important for the survival, growth, development and reproduction of aquatic animals.Methods: In this study, a comparative transcriptome analysis (maintained for 45 days in three different salinities, 30 psu (HC group), 18 psu (MC group) and 3 psu (LC group)) was performed by high-throughput sequencing of economically cultured Penaeus monodon. P. monodon gill tissues from each treatment were collected for RNA-seq analysis to identify potential genes and pathways in response to low salinity stress.Results: A total of 64,475 unigenes were annotated in this study. There were 1,140 upregulated genes and 1,531 downregulated genes observed in the LC vs. HC group and 1,000 upregulated genes and 1,062 downregulated genes observed in the MC vs. HC group. In the LC vs. HC group, 583 DEGs significantly mapped to 37 signaling pathways, such as the NOD-like receptor signaling pathway, Toll-like receptor signaling pathway, and PI3K-Akt signaling pathway; in the MC vs. HC group, 444 DEGs significantly mapped to 28 signaling pathways, such as the MAPK signaling pathway, Hippo signaling pathway and calcium signaling pathway. These pathways were significantly associated mainly with signal transduction, immunity and metabolism.Conclusions: These results suggest that low salinity stress may affect regulatory mechanisms such as metabolism, immunity, and signal transduction in addition to osmolarity in P. monodon. The greater the difference in salinity, the more significant the difference in genes. This study provides some guidance for understanding the low-salt domestication culture of P. monodon.

Starvation is a common stress in fish that is caused by environmental changes, and refeeding after starvation is believed to cause compensatory growth. Here, we evaluated the impacts of starvation for 7 d, followed by refeeding for 7 d on growth, gut microbiome, biochemical indices, liver transcriptome, and immune response in golden pompanos (Trachinotus ovatus). Starvation induced hypoglycemia, reduced triglyceride concentration, and considerably affected the activities of glycolysis related enzymes, including glucokinase (GK), pyruvate kinase (PK), and fructokinase 6-phosphate (PFK). Additionally, starvation for 7 d increased the concentrations of oxidative stress indicators, including cortisol (COR), superoxide dismutase (SOD), malondialdehyde (MDA), and catalase (CAT) and non-specific immunity parameters, including alkaline phosphatase (ALP), acid phosphatase (ACP), and lysozyme (LYZ). parameters to normal levels. Moreover, starvation affected the diversity and composition of the intestinal microbiota of T. ovatus. At the phylum level, the dominant phyla were Proteobacteria, Spirochaetes, and Tenericutes, while the dominant genera were Brevinema, Haematospirillum, and Mycoplasma. Transcriptome analysis of liver tissues showed that the mRNA expression of GK, PK, and PFK, were altered by starvation, and the trends were consistent with the activity levels of the enzymes. A total of 2,287 DEGs were identified among the control, starvation, and refeeding groups. DEGs in starvation (ST7) vs. control (CK) groups were mainly involved in cell cycle, DNA replication, and mitosis, whereas those in the refeeding (RT7) vs. ST7 groups were associated with stimulus responses and carbohydrate metabolism. Overall, most starvation-induced changes in enzyme activity, intestinal microbiome, immune response, and liver transcriptome were gradually restored to normal after refeeding for 7 d. These data provide a theoretical reference for the farming of T. ovatus during periods of feed scarcity.

Tumour necrosis factor-α (TNFα) is a multifarious mediator of lymphoid tissue growth and antimicrobial defence mechanisms, and it acts as a pro-inflammatory regulator. The function of TNFα in parasite infection and the underlying mechanism through which nuclear factor-κB (NF-κB) regulates TNFα remain largely unclear in teleosts. In the present study, TNFα (ToTNFα) from golden pompano (Trachinotus ovatus) was identified, and its sequence features and expression levels were determined. The genomic DNA sequence is composed of 1,130 bp, consists of four exons and three introns, and encodes 341 amino acid polypeptides. The putative protein sequence shares 34.7%–61.9% identity with fish TNFα and possesses a TNF family signature and two conserved cysteine residues. Moreover, the expressions of ToNF-κB and ToTNFα are constitutively expressed in all examined tissues, with higher levels observed in the immune relevant tissues. Both ToNF-κB and ToTNFα transcription was increased in the local infection sites (skin and gill) and system immune tissues (liver, spleen and head kidney) after Cryptocaryon irritans stimulation. In addition, to investigate whether ToNF-κB is a regulator of ToTNFα, promoter analysis was performed. The region from -970 to +79 bp is known as the core promoter by different truncated mutants of ToTNFα. Subsequently, the activity of the ToTNFα-p2 promoter was dramatically reduced after targeted mutation of the M6-binding site. Additionally, an electrophoretic mobile shift assay (EMSA) verified that ToNF-κB interacted with the M6-binding site in the ToTNFα promoter region to control the expression of ToTNFα. In conclusion, the present study provides the positive regulation of TNFα transcription by NF-κB and contributes to a better understanding of the transcriptional mechanism of TNFα in fish.

The golden pompano (Trachinotus ovatus) is one of the most economically valuable marine fishes in South China. Streptococcus agalactiae, an infectious Gram-positive bacterium that is highly destructive for golden pompano culture, has recently caused massive losses to the golden pompano industry. This study aimed to investigate the dynamic immune response of golden pompano to S. agalactiae infection, using RNA-seq analysis at two different time points after infection. Abundances of differentially expressed genes (DEGs) gradually increased in the liver and spleen 48–120 h post-infection, whereas those in the head kidney were lower at 120 h than at 48 h. Pathway enrichment analysis of DEGs revealed that genes related to the complement system were continuously transcribed between 48 and 120 h. Metabolic and immune-regulation-related pathways were highly enriched in the liver 48 h after infection. Transcriptome analysis was verified using quantitative PCR for eight genes with similar expression trends. This study revealed the inflammatory response of golden pompano after S. agalactiae infection, including inflammation-related chemokines and signaling pathways. Our findings provide a theoretical basis for studying S. agalactiae resistance in golden pompano and provide a reliable resource for the genetic breeding of fish.

As a highly conserved transcription factor family, DMRTs (Doublesex and Mab-3-related transcription factors) are involved in sex determination and sexual differentiation in numerous animals. In the present study, we identified a DM (Doublesex/Mab-3)-domain gene in Penaeus monodon, which we named PmDMRT11E because it shared many similarities with DMRT11E homologs and has a close relationship in the phylogeny of different species. The three-dimensional structure and amino acid alignments indicated the stability and conservation of the DM domain. Real-time PCR analysis revealed that PmDMRT11E was highly and preferentially expressed in the testis of sub-adult shrimp. During embryogenesis, the expression level of PmDMRT11E was higher at the nauplius than at other periods. PmDMRT11E dsRNA injection significantly decreased the transcription factor Sox9 and increased ovarian marker Foxl2 expression, implying its important regulatory role in the mechanism of male determination. Moreover, dsDMRT11E caused abnormal sperm development, indicating that PmDMRT11E may be closely related to gonadal development and spermatogenesis.

Abstract Next‐generation sequencing has greatly promoted the investigation of single nucleotide polymorphisms, while studies of simple sequence repeats are sharply decreasing. However, simple sequence repeats still present some advantages in conservation genetics. In this study, an end‐to‐end pipeline referred to as MultiplexSSR was established to develop multiplex PCR assays in batches with highly polymorphic simple sequence repeats for capillary platforms from resequencing data. The distribution of single sequence repeats in the genome, the error profiles of genotypes and allelotypes, and the increase in the allele length range depending on the number of individuals were investigated. A total of 98% of single sequence repeats presented lengths of less than 100 bp. The error rate of the genotyping and allelotyping of dimeric patterns was ten times higher than those for other patterns. The error rate of allelotyping was less than that of genotyping. The allele length range reached approximate saturation with 10 individuals. This pipeline uses allele numbers to select highly polymorphic loci, masks loci with variation, and applies in silico PCR to improve primer specificity. The application of the developed multiplex SSR‐PCR assays validated the pipeline's robustness, showing higher polymorphism and stability for the developed simple sequence repeats and a lower cost for genotyping and providing low‐depth resequencing data from less than a dozen individuals for the development of markers. This pipeline fills the gap between next‐generation sequencing and multiplex SSR‐PCR.

This study aimed to investigate the intoxication mechanism of golden pompano (Trachinotus ovatus) exposed to high ammonia levels and the effects on the immune and antioxidant mechanisms of gills. Juvenile golden pompano was exposed to ammonia (total ammonia: 26.9 mg/L) to induce 96 h of ammonia stress, and a 96 h recovery experiment was performed after poisoning. Then, we evaluated hematological parameters, the histological structure and the expression of related genes. In this experiment, continuous exposure to high levels of ammonia led to a significant increase in plasma alkaline phosphatase (ALP), acid phosphatase (ACP) and lactate dehydrogenase (LDH) levels (P

Doublesex (Dsx) is a polymorphic transcription factor of the DMRTs family, which is involved in male sex trait development and controls sexual dimorphism at different developmental stages in arthropods. However, the transcriptional regulation of the Dsx gene is largely unknown in decapods. In this study, we reported the cDNA sequence of PmDsx in Penaeus monodon, which encodes a 257 amino acid polypeptide. It shared many similarities with Dsx homologs and has a close relationship in the phylogeny of different species. We demonstrated that the expression of the male sex differentiation gene Dsx was predominantly expressed in the P. monodon testis, and that PmDsx dsRNA injection significantly decreased the expression of the insulin-like androgenic gland hormone (IAG) and male sex-determining gene while increasing the expression of the female sex-determining gene. We also identified a 5′-flanking region of PmIAG that had two potential cis-regulatory elements (CREs) for the PmDsx transcription. Further, the dual-luciferase reporter analysis and truncated mutagenesis revealed that PmDsx overexpression significantly promoted the transcriptional activity of the PmIAG promoter via a specific CRE. These results suggest that PmDsx is engaged in male reproductive development and positively regulates the transcription of the PmIAG by specifically binding upstream of the promoter of the PmIAG. It provides a theoretical basis for exploring the sexual regulation pathway and evolutionary dynamics of Dmrt family genes in P. monodon.

Longfin batfish (Platax teira) is a coastal marine fish life. The aims of this study are to investigate the compositions and content of amino acid and fatty acid in three parts of P. teira. The results showed that P. teira muscle protein content was as high as 21.00%. For amino acid composition, seventeen kinds of amino acids were detected in three parts. The essential amino acid score (EAAS) and essential amino acids (EAA) / total amino acids (TAA) ratio of P. teira were both above 70 and 0.4. EAAS in the upper part of the abdominal muscle showed higher than those two parts. The content of saturated fatty acids (SFA) and the polyunsaturated fatty acids (PUFA) in the upper part of the abdominal muscle was higher than that in other groups. No significant differences in monounsaturated fatty acids (MUFA) and n-3/n- 6 were detected among three parts. Overall, the upper part of the abdominal muscle was thought to have a higher nutritious value. These results showed P. teira is a high quality marine fish with high protein content and low fat, abundant amino acids with proper proportion, however, it was regarded as an excellent breeding varieties.

The black tiger shrimp, Penaeus monodon, is important in both fishery and aquaculture and is the second-most widely cultured shrimp species in the world. However, the current strains cannot meet the market needs in various cultural environments, and the genome resources for P. monodon are still lacking. Restriction-site associated DNA sequencing (RADseq) has been widely used in genetic linkage map construction and in quantitative trait loci (QTL) mapping. We constructed a high-density genetic linkage map with RADseq in a full-sib family. This map contained 6524 single nucleotide polymorphisms (SNPs) and 2208 unique loci. The total length was 3275.4 cM, and the genetic distance was estimated to be 1.1 Mb/cM. The sex trait is a dichotomous phenotype, and the same interval was detected as a QTL using QTL mapping and genome-wide association analysis. The most significant locus explained 77.4% of the phenotype variance. The sex locus was speculated to be the same in this species based on the sequence alignments in Mozambique, India, and Hawaii populations. The constructed genetic linkage map provided a valuable resource for QTL mapping, genome assembly, and genome comparison for shrimp. The demonstrated common sex locus is a step closer to locating the underlying gene.

The nuclear peroxisome proliferator-activated receptors (PPARs) regulate the transcription of elongases of very long-chain fatty acids (Elovl), which are involved in polyunsaturated fatty acid (PUFA) biosynthesis in mammals. In the present study, we first characterized the function of Elovl5 elongase in Trachinotus ovatus. The functional study showed that ToElovl5 displayed high elongation activity toward C18 and C20 PUFA. To investigate whether PPARαb was a regulator of Elovl5, we also reported the sequence of T. ovatus PPARαb (ToPPARαb). The open reading frame (ORF) sequence encoded 469 amino acids possessing four typical characteristic domains, including an N-terminal hypervariable region, a DNA-binding domain (DBD), a flexible hinge domain and a ligand-binding domain (LBD). Thirdly, promoter activity experiments showed that the region from PGL3-basic-Elovl5-5 (-146 bp to +459 bp) was defined as the core promoter by progressive deletion mutation of Elovl5. Moreover, PPARαb overexpression led to a clear time-dependent enhancement of ToElovl5 promoter expression in HEK 293T cells. Fourth, the agonist of PPARαb prominently increased PPARαb and Elovl5 expression, while PPARαb depletion by RNAi or an inhibitor was correlated with a significant reduction of Elovl5 transcription in T. ovatus caudal fin cells (TOCF). In conclusion, the present study provides the first evidence of the positive regulation of Elovl5 transcription by PPARαb and contributes to a better understanding of the transcriptional mechanism of PPARαb in fish.

Toll-like receptors (TLRs), as important pattern recognition receptors, represent a significant component of fish immune systems and play an important role in resisting the invasion of pathogenic microorganisms. The TLR5 subfamily contains two types of TLR5, the membrane form of TLR5 (TLR5M) and the soluble form of TLR5 (TLR5S), whose detailed functions have not been completely elucidated. In the present study, we first identified two genes, TLR5M (ToTLR5M) and TLR5S (ToTLR5S), from golden pompano (Trachinotus ovatus). The full-length ToTLR5M and ToTLR5S cDNA are 3644 bp and 2329 bp, respectively, comprising an open reading frame (ORF) of 2673 bp, encoding 890 amino acids, and an ORF of 1935 bp, encoding 644 amino acids. Both the ToTLR5s possess representative TLR domains; however, only ToTLR5M has transmembrane and intracellular TIR domains. Moreover, the transcription of two ToTLR5s was significantly upregulated after stimulation by polyinosinic:polycytidylic acid (poly (I:C)), lipopolysaccharide (LPS), and flagellin in both immune-related tissues (liver, intestine, blood, kidney, and skin) and nonimmune-related tissue (muscle). Furthermore, the results of bioinformatic and promoter analysis show that the transcription factors GATA-1 (GATA Binding Protein 1), C/EBPalpha (CCAAT Enhancer Binding Protein Alpha), and ICSBP (Interferon (IFN) consensus sequence binding protein) may play a positive role in moderating the expression of two ToTLR5s. Overexpression of ToTLR5M and ToTLR5S notably increases NF-κB (nuclear factor kappa-B) activity. Additionally, the binding assay revealed that two rToTLR5s can bind specifically to bacteria and pathogen-associated molecular patterns (PAMPs) containing Vibrio harveyi, Vibrio anguillarum, Vibrio vulnificus, Escherichia coli, Photobacterium damselae, Staphylococcus aureus, Aeromonas hydrophila, LPS, poly(I:C), flagellin, and peptidoglycan (PGN). In conclusion, the present study may help to elucidate the function of ToTLR5M/S and clarify their possible roles in the fish immune response to bacterial infection.

Interferon (IFN) regulatory factor 1 (IRF1), a transcription factor with a novel helix–turn–helix DNA-binding domain, plays a crucial role in innate immunity by regulating the type I IFN signaling pathway. However, the regulatory mechanism through which IRF1 regulates type I IFN in fish is not yet elucidated. In the present study, IRF1 was characterized from golden pompano, Trachinotus ovatus (designated ToIRF1), and its immune function was identified to elucidate the transcriptional regulatory mechanism of ToIFNa3. The full-length complementary DNA (cDNA) of IRF1 is 1763 bp, including a 900-bp open reading frame (ORF) encoding a 299-amino-acid polypeptide. The putative protein sequence has 42.7–71.7% identity to fish IRF1 and possesses a representative conserved domain (a DNA-binding domain (DBD) at the N-terminus). The genomic DNA sequence of ToIRF1 consists of eight exons and seven introns. Moreover, ToIRF1 is constitutively expressed in all examined tissues, with higher levels being observed in immune-relevant tissues (whole blood, gill, and skin). Additionally, Cryptocaryon irritans challenge in vivo increases ToIRF1 expression in the skin as determined by Western blotting (WB); however, protein levels of ToIRF1 in the gill did not change significantly. The subcellular localization indicates that ToIRF1 is localized in the nucleus and cytoplasm with or without polyinosinic/polycytidylic acid (poly (I:C)) induction. Furthermore, overexpression of ToIRF1 or ToIFNa3 shows that ToIRF1 can notably activate ToIFNa3 and interferon signaling molecule expression. Promoter sequence analysis finds that several interferon stimulating response element (ISRE) binding sites are present in the promoter of ToIFNa3. Additionally, truncation, point mutation, and electrophoretic mobile shift (EMSA) assays confirmed that ToIRF1 M5 ISRE binding sites are functionally important for ToIFNa3 transcription. These results may help to illuminate the roles of teleost IRF1 in the transcriptional mechanisms of type I IFN in the immune process.

Fatty acid desaturases are rate-limiting enzymes in long-chain polyunsaturated fatty acid biosynthesis. The transcription factor peroxisome proliferator-activated receptor alpha b (PPARαb) regulates lipid metabolism in mammals, however, the mechanism whereby PPARαb regulates fatty acid desaturases is largely unknown in fish. In this study, we report the full length cDNA sequence of Trachinotus ovatus fatty acid desaturase, which encodes a 380 amino acid polypeptide, possessing three characteristic histidine domains. Phylogenetic and gene exon/intron structure analyses showed typical phylogeny: the T. ovatus fatty acid desaturase contained a highly conserved exon/intron architecture. Moreover, functional characterization by heterologous expression in yeast indicated that T. ovatus desaturase was a fatty acid desaturase, with Δ4/Δ5/Δ8 Fad activity. Promoter activity assays indicated that ToFads6 desaturase transcription was positively regulated by PPARαb. Similarly, PPARαb RNA interference decreased ToPPARαb and ToFads6 expression at the mRNA and protein levels in a time-dependent manner. Mutation analyses showed that the M2 binding site of PPARαb was functionally important for protein binding, and transcriptional activity of the ToFads6 promoter was significantly decreased after targeted mutation of M2. Electrophoretic mobile shift assays confirmed that PPARαb interacted with the binding site of the ToFads6 promoter region, to regulate ToFads6 transcription. In summary, PPARαb played a vital role in ToFads6 regulation and may promote the biosynthesis of long-chain polyunsaturated fatty acids by regulating ToFads6 expression.

The experiment simulated the logistical transportation of Penaeus monodon. It set four distinct gradient Vitamin C (Vc) addition levels, including 0mg/L, 111mg/L, 222mg/L, and 333mg/L, to investigate the impact of Vc on the anti-stress ability of P. monodon during transportation. And the survival rate following transportation and a 15-day interim rearing period were recorded. Moreover, the alterations in tissue structure and activity of the enzymes alkaline phosphatase (ACP), alkaline phosphatase (AKP), total superoxide dismutase (T-SOD), and total superoxide dismutase (T-AOC) were checked. The results showed that with the increase of Vc supplemental level, the survival rate of P. monodon after transportation and after 15 days of temporary rearing increased to varying degrees. ACP and AKP in the hepatopancreas increased first and then decreased. T-SOD activity in the 0mg/L group was the lowest and then decreased gradually. The activity of total antioxidant capacity (T-AOC) in the 0mg/L group was the lowest and then stabilized. The branchial tissue structure also changed. The branchial tissue blood cell disorder decreased, the diaphragm gradually narrowed, the cornered cortex gradually recovered, and the swelling decreased. In conclusion, Vc positively affects the survival rate of P. monodon after transportation and temporary cultivation and alleviates the stress of P. monodon. The amount of Vc added at about 333mg/Lin, the transportation of P. monodon could play a positive role. The experimental results provide primary data for the transportation of P. monodon. [ABSTRACT FROM AUTHOR]

In this study, three genes, PmATP synthase, PmNa+-K+-ATPase and PmToll receptor gene, were selected to study their relative expression in different tissues of Penaeus monodon. The results showed that the mRNA level of PmATP synthase gene was not significantly up-regulated under low salt stimulation (P> 0.05),while under high salinity stimulation, the transcription level of PmATP synthase mRNA reached the maximum at 16th h (P<0.05).The expression level of PmNa+-K+-ATPase mRNA increased at 4th h and 16th h, which was significantly higher than that in the beginning under low salt stimulation (P<0.05) and then decreased at 32nd h,,while under high salinity stimulation, the expression level of PmNa+-K+- ATPase mRNA reached the highest at 8th h and 32nd h. The expression level of PmToll receptor mRNA reached the highest at 4th h after low salinity stimulation (P<0.05), and then down-regulated after 16th h, while under high salinity stress, the expression level was up-regulated and reached the maximum at 8th h, which was 2.4 times of that the in the control group (P<0.05) and decreased at 16th h after stress. PmATP synthase gene was relatively high expression, while PmNa+-K+-ATPase and PmToll receptor gene expression were low, so we guess that the large amounts of ATP of the body synthesis mainly use for the growth of the body. PmNa+-K+-ATPase and PmToll receptor gene expression are relatively high, which indicate that the body osmotic pressure regulation and the body’s immune process consume a lot of energy [ABSTRACT FROM AUTHOR]

Traditional broodstock diets, being susceptible to virus attacks or carrying the virus to parent shrimps, bring a huge bio-security risk to shrimp breeding. This study was carried out to determine the feasibility of Pheretima tschiliensis as a replacement of traditional bait to accelerate the maturity of parent shrimps of Penaeus monodon, which was verified by the dynamics of vitellogenin gene expression in hepatopancreas and ovary of P. monodon. The parent shrimps fed on four different diets including commercial parent shrimps feed (Diet A), Pheretima tschiliensis combination bait (Diet B), Pheretima tschiliensis (Diet C) and Nereis succinea combination bait (Diet D), and the effect of each diet on the maturity of parent shrimps was evaluated by testing the gonad weight increase rate, eggs amount, average spawning time and levels of VTG mRNA expression. The results showed that P. tschiliensis, as a closely related terrestrial species of N. succinea, had the best effect on maturation of parent shrimps. The highest gonad weight increase rate of 1845.28% and the largest consecutive spawning rate with average value of 70.66% were both in groups fed on P. tschiliensis, with no significant difference from the groups fed on N. succinea combination bait. The dynamics of VTG mRNA level were observed in hepatopancreas and ovary of P. monodon with the trend of increasing firstly and then decreasing, which reflected reproductive performance of the parent shrimps and was suggested to be an indicator of reproductive performance for selective breeding. As a result, P. tschiliensis is a suitable substitute of N. succinea based on its effect on the reproductive traits and VTG mRNA expression level in parent shrimps of P. monodon. [ABSTRACT FROM AUTHOR]

This study examined the growth response of black tiger shrimp, Penaeus monodon, reared in indoor cement ponds fed at variable daily feeding frequencies. Five hundred healthy shrimp (1.26±0.37 g initial weight) were stocked in 12 cement ponds (5.5x2.5x1.5m). Three ponds in each group were assigned to four different feeding frequency i.e., two, three, four and six times/day designated as FF1, FF2, FF3 and FF4, respectively. Artificial diet (40% fishmeal protein) was used to feed at eight percent of total shrimp body weight per day for a total period of 56 days. The shrimp length and weight were measured fortnightly and the feeding rate was adjusted according to the new weight. At the end of the trial, all shrimp remained healthy and active with the survival rate of 70-85%. The specific growth rate (SGR) were the highest in groups FF3 (4.21±0.53) and FF4 (4.23±1.04), which were significantly higher than those in FF1 (3.82±0.49) and FF2 (4.02±1.03) groups. Whole body proximate composition (protein, ash, moisture and lipid) remained similar in all the treatment groups. It could be concluded that the black tiger shrimp, P. monodon, would be grown in indoor cement ponds effectively by feeding four times day-1 to achieve significantly better growth. [ABSTRACT FROM AUTHOR]

The fertilized eggs of "Nanhai 2" Penaeus monodon bred by our research group were incubated at the same temperature (30°C), different salinity (20, 25, 30, 35, 40), different pH (7.0, 7.5, 8.0, 8.5, 9.0) and different alkalinity (2.0 mmol/L, 2.5 mmol/L, 3.0 mmol/L, 3.5 mmol/L, 4.0 mmol/L) to explore the effects of salinity, pH and alkalinity on hatching rate of fertilized eggs of P. monodon. The results showed that the hatching rate of fertilization rate of P. monodon was closely related to salinity, and the best hatching rate was obtained when the seawater salinity was 30 with the average hatching rate was 82.60%. The hatching rate was very low when the salinity was as low as 20 or as high as 40, which was significantly lower than that of other treatments (P<0.05). The hatching effect of the fertilized eggs of P. monodon was closely related to the pH value of seawater, and the slightly alkaline seawater was conducive to the normal development of the fertilized eggs. Among them, the hatching effect of the seawater pH value of 8.0 was the best, and the average hatching rate of the fertilized eggs was 80.62%. Too low or too high pH value of the seawater was not conducive to the development of the embryo, and the hatching rate of the fertilized eggs decreased in varying degrees. There was no significant correlation between the hatching effect of fertilized eggs and the change of seawater alkalinity. The average hatching rate of fertilized eggs ranged from 78.65% to 83.12% in the alkalinity range of 2.0-4.0 mmol/L. [ABSTRACT FROM AUTHOR]

To explore the effect of concentrated dephenolic cottonseed protein (CDCP) partly instead of fish meal on the non-specific immune of Penaeus monodon, we designed a single factor test to study the four types of non-specific immunity of P. monodon hepatopancreas after acute salinity stress. A total number of 5,400 P. monodon were selected with an initial body weight of 1.76±0.15g and randomly divide into 6 groups (3 replicates per group, 900 tails per replicate). Shrimp were feed with two protein level diets (Diet A and Diet B). After 8 weeks of feeding, P. monodon were randomly selected with an average weight of 14.71±1.06g in each feed group, and subjected to acute salinity stress of 10ppt and 20ppt after temporary rearing, and the heat shock protein 70 (HSP70), Na+-K+-ATPase, cortisol and the content of alkaline phosphatase (ALP) were measured. The results of the study showed that when the CDCP partially replaced fish meal of P. monodon diet, the hepatopancreas HSP70, and the contents of Na+-K+-ATPase and cortisol were significantly higher than those of the control group. In the acute salinity change, there was no significant difference in the survival rate of P. monodon at 48h under the two salinity stresses, and the four immune indexes showed different trends. The expression level of Cortisol was more prominent than that of HSP70, which could better reflect the stress degree of P. monodon. Most of the indicators showed a trend of rising and then falling and then rising compared with the original level, and the changes of the four indicators of hepatopancreas in the Diet B group were significantly higher than those in the Diet A group at most time point of the two salinities. [ABSTRACT FROM AUTHOR]

The impacts of temperature on oxygen and energy metabolism in the hepatopancreas of the black tiger shrimp (Penaeus monodon) were investigated via the effects of thermal stress on superoxide anion (O2-) production, superoxide dismutase (SOD) activity, glutathione (GSH) and adenosine triphosphate (ATP) concentration, as well as nitric oxide synthase (NOS) activity and nitric oxide (NO) concentration catalyzed by NOS. Based on biochemical analysis of the above, results showed that O2- production could be induced significantly after cold stress at 15°C and heat stress above 30°C. SOD activity showed a similar changing profile as the concentration of O2- after thermal stress between 15°C and 30°C, and GSH concentration increased significantly under both high and low temperature. The NOS activity and concentration of NO catalyzed by NOS increased significantly after heat stress. The ATP concentration increased significantly after both low and high temperature stress, but returned to the control level after 8 h of recovery. Thus, low and high temperature stress could lead to oxygen metabolism disorder in the hepatopancreas of P. monodon, which might induce antioxidant enzyme responses. Our findings suggest that SOD and GSH might play different roles in the response of the shrimp to low and high temperature, whereas NO might play an important role in the induction of many signaling pathways in response to thermal stress. Additional ATP was also produced after cold and heat stress, suggesting that more energy was required to cope with temperature extremes. Our findings indicate that temperature stress led to oxygen metabolism disorder, possibly due to the temperature being beyond the oxygen- and capacitylimitation of thermal tolerance of P. monodon. Oxygen metabolism disruption might also impact energy metabolism and other physiological activities in P. monodon. [ABSTRACT FROM AUTHOR]