Giant River Prawn Macrobrachium Rosenbergii Research Articles

Utilization of different lysine isomers: A case study on the growth, metabolic enzymes, antioxidant capacity and muscle amino acid composition in Macrobrachium rosenbergii

An 8-week feeding trial was conducted to compare the effects of different lysine isomers on growth performance, amino acid metabolism-related enzyme activities, antioxidant capacity and muscle amino acid composition of giant river prawn (Macrobrachium rosenbergii). The basal diet was formulated to be low in lysine and contained only 10.9 g/kg lysine. The other three experimental diets were supplemented with 12 g/kg D-lysine, L-lysine, and DL-lysine, respectively. Dietary lysine supplementation improved the growth rate and feed utilization of M. rosenbergii, but significant differences were only found between the prawn fed the control diet and the L-lysine diet. L-lysine supplementation significantly improved the intestinal and hepatic trypsin activities, but unaffected the lipase and amylase activities. The highest hepatic aspartate aminotransferase and alanine aminotransferase activities were observed in prawn fed the L-lysine diet, whereas the highest γ-glutamyl transferase activity was found in prawn fed the D-lysine diet. D-lysine supplementation significantly increased the intestinal and hepatic D-amino acid oxidase activities. However, L-lysine supplementation improved the hepatic lysozyme activity and total antioxidant capacity, depressed the hepatic lactate dehydrogenase and alkaline phosphatase activities. Conversely, D-lysine supplementation generally depressed the hepatic superoxide dismutase and peroxidase activities, and nitric oxide content. Furthermore, L-lysine supplementation increased the muscle aspartic acid, serine, glutamic acid, alanine, lysine, arginine, delicious amino (DAA), non-essential amino acids, total amino acids (TAA) contents and DAA/TAA ratio. These results indicate that M. rosenbergii can effectively utilize L-lysine for growth; D-lysine may partly be used but reveal specific toxic effects on antioxidant response.

Survival and metamorphosis of giant river prawn Macrobrachium rosenbergii larvae in a commercial recirculation system with artificial seawater

Larval production of giant river prawn Macrobrachium rosenbergii and water quality in a commercial hatchery using a closed recirculation system (RAS) with artificial seawater, considering water used during 240 days (E1) and freshly prepared water (E2), was evaluated. An average of 100 larvae L−1 (zoea I) was stocked in four tanks of 1000 L; in both treatments, they were fed Artemia and egg custard. Survival and larval stage index (LSI) were estimated, every 5 days. Temperature, salinity and pH were monitored daily, while nitrogen compounds and ions were monitored every 5 days. Spearman and Pearson correlations were performed between larval survival and ion concentration and Mg/Ca ratio. Final larval survival differed significantly between treatments E1 (32% ± 7.5%) and E2 (50% ± 7.5%). Larval cycle lasted 23 and 21 days for E1 and E2 respectively. LSI did not differ significantly between the treatments. Water quality parameters were appropriate for the specie, although nitrate (NO3) increased to 500 mg L−1 in E1 treatment. Reused water showed a depletion of magnesium (~half of it) when compared to freshly prepared water. Magnesium and potassium concentrations decreased in both treatments during E1 cycle. A positive correlation was found between larval survival and magnesium (r = 0.54) and potassium (r = 0.78) in E1, but the same was not observed in E2. Mg/Ca ratio in E1 showed an average of 1.2, whereas, in E2, the average ratio was 2.1. The depletion of magnesium and potassium ions, through the continuous use of the water in RAS, could affect the survival of larvae.

Functional and Stress Response Analysis of Heat Shock Proteins 40 and 90 of Giant River Prawn (Macrobrachium rosenbergii) under Temperature and Pathogenic Bacterial Exposure Stimuli.

The aims of this research were to perform molecular characterization and biofunctional analyses of giant river prawn Hsp40 and Hsp90 genes (Mr-hsp40 and Mr-hsp90) under various stress conditions. Comparisons of the nucleotide and amino acid sequences of Mr-hsp40 and Mr-hsp90 with those of other species showed the highest similarity scores with crustaceans. Under normal conditions, expression analysis using quantitative real-time RT-PCR (qRT-PCR) indicated that Mr-hsp40 was highly expressed in the gills and testis, and Mr-hsp90 expression was observed in all tissues, with the highest expression in the ovary. The expression patterns of Mr-hsp40 and Mr-hsp90 transcripts under Aeromonas hydrophila challenge and heat–cold shock conditions were examined in gills, the hepatopancreas and hemocytes, at 0, 3, 6, 12, 24, 48 and 96 h by qRT-PCR. Under bacterial challenge, Mr-hsp40 displayed variable expression patterns in all tissues examined during the tested periods. In contrast, upregulated expression of Mr-hsp90 was quickly observed from 3 to 12 h in the gills and hepatopancreas, whereas obviously significant upregulation of Mr-hsp90 was observed in hemocytes at 12–96 h. Under temperature shock conditions, upregulation of Mr-hsp40 expression was detected in all tested tissues, while Mr-hsp90 expression was quickly upregulated at 3–48 h in all tissues in response to 35 °C conditions, and conditions of 35 and 25 °C stimulated its expression in gills and the hepatopancreas at 12 and 48 h, respectively. Silencing analyses of these two genes were successfully conducted under normal, high-temperature (35 °C) and A. hydrophila infection conditions. Overall, knockdown of Mr-hsp40 and Mr-hsp90 effectively induced more rapid and higher mortality than in the PBS control and GFP induction groups in temperature and infectious treatments. Evidence from this study clearly demonstrated the significant functional roles of Mr-hsp40 and Mr-hsp90, which are crucially involved in cellular stress responses to both temperature and pathogenic bacterial stimuli.

Proteomic analysis of individual giant freshwater prawn, Macrobrachium rosenbergii, growth retardants

“Iron prawn” is a condition of severe growth retardation that fishers call. The giant river prawn (Macrobrachium rosenbergii) is a commercially important species contains high protein content and functional nutrients. However, no proteomic information is available for this species. We performed the shotgun 2DLC-MS/MS proteomic analysis of the total protein from “iron prawn”. Total 19,758 peptides corresponding to 2613 high-confidence proteins were identified. These proteins range in size from 40 to 70 kDa. KEGG analysis revealed that the largest group consisting total 102 KEGG pathway proteins comparing the “iron prawn” with the normal prawn. Additionally, 7, 11, 1, 6, and 5 commercially important enzymes were found in the eyestalk, liver, muscle, ovary, and testis, respectively. The functions of these differently expressed enzymes include immune system action against pathogens, muscle contraction, digestive system metabolism, cell differentiation, migration, and apoptosis in the severe growth retardation of “iron prawn”. Our work provides insight into the understanding of the formation mechanism of “iron prawn”.

Effect of a prawn (Macrobrachium rosenbergii)-plant eco-symbiotic culture system (PECS) on intestinal microbiota, organic acids, and ammonia

Prawn-plant eco-symbiotic culture system (PECS) is an efficient symbiotic culture system, in which prawn and plants are placed in the same culture space according to a certain proportion. In the study, the potential of PECS to impact microbial communities and metabolites in the intestine of cultured giant river prawn Macrobrachium rosenbergii is assessed. We found that the growth parameters (such as length gain, weight gain and specific growth rate) of PECS with 15 % feed ratio were significantly improved by 4 week culture. And PECS modulated growth profiles of Lactobacillus, Bifidobacterium, Atopobium cluster, and Roseburia subcluster bacteria, all of which increased significantly with 15 % feed ratio in the intestines of M. rosenbergii. Growth of Faecalibacterium prausnitzii, and bacteria referable to the Desulfovibrionales and Desulfuromonadales, were influenced by PECS, whereas growth of Clostridium histolyticum and C. coccoides/Eubacterium rectale groups were not significantly affected. PECS with 15 % feed ratio positively impacted short-chain fatty acids (SCFA) and branched-chain fatty acids (BCFA) production, and reduced lactate levels, without causing any ammonia cytotoxic effects. Well growth performance of the prawn was consistent with increase in intestinal benefit microbiota. In general, PECS (with a feed ratio of 15 %) proved to be beneficial for promoting organic acids and growth performance via modulated intestinal microbiota, indicating PECS with reasonable feed ratio represent a promising alternative to traditional pond monoculture of M. rosenbergii.

Effects of Microplastics, Polystyrene, and Polyethylene on Antioxidants, Metabolic Enzymes, HSP-70, and Myostatin Expressions in the Giant River Prawn Macrobrachium rosenbergii: Impact on Survival and Growth.

This study was conducted to understand the biological effects of microplastics (MPs), polystyrene microspheres (PSM), and polyethylene microparticles (PEM) in the juveniles of the giant river prawn, Macrobrachium rosenbergii. The PSM (0.5-1.0µm) and PEM (30.0-150.0µm) were separately incorporated into the artificial diets with concentrations of 1, 5, and 10mg per 100g. The prawns were fed with these diets for a period of 60days. Compared with control, the following dose-dependent changes have been recorded in PSM and PEM incorporated feeds fed prawns: declines in the survival rate, length and weight gains; increase in activities of antioxidant enzymes, such as superoxide dismutase, catalase, glutathione s-transferase, and glutathione peroxidase (GPx); elevated concentrations of reduced glutathione (GSH) and malondialdehyde; decreased activities of metabolic enzymes, such as glutamic oxaloacetic transaminase and glutamic pyruvic transaminase; higher total RNA in hepatopancreas (HP) of PSM fed prawns compared with that of PEM; higher total RNA in muscle (MU) of PEM-fed prawns compared with that of PSM; prominent cDNA bands in 150bp regions; up-regulated heat shock protein (HSP70) gene in HP; down-regulation of HSP70 gene in MU of PSM-fed prawns only; down-regulated myostatin (MSTN) gene. These results suggest that these MPs have affected the survival and growth, activated the antioxidant defense, inhibit the metabolic enzymes, positively regulated the HSP70 gene, and negatively regulated the MSTN gene in M. rosenbergii. Therefore, exposures to PSM and PEM caused biological effects in this species of prawn.

Effects of carbon sources on the culture of giant river prawn in biofloc system during nursery phase

A six-week nursery culture of giant river prawn Macrobrachium rosenbergii was conducted in a zero-water exchange biofloc technology (BFT) system. Water quality, microorganisms, proximate composition and growth performance of prawn were compared by using five different carbon sources: wheat bran (WB), rice flour (RF), molasses (MO), maize starch (MS) and palm kernel expeller (PKE). These carbon sources were added at a carbon-nitrogen ratio of 15:1. Fifteen 125 L polyethylene tanks with water volume of 100 L were used for this experiment. Each tank was stocked with 100 postlarvae (average initial weight 21.9 ± 2.3 mg). Each treatment was randomly assigned in triplicate. The water quality parameters viz. temperature, pH, dissolved oxygen and ammonia-N did not differ (P > 0.05) among five different carbon treatments. MO based BFT system had significantly (P < 0.05) lowest nitrite-N and the highest biofloc volume than other treatments. The postlarval survival (88.6 %) was significantly higher (P < 0.05) in MS treatment and followed by RF (73.0 %), MO (68.3 %), WB (61.0 %) and PKE (56.3 %) treatments, respectively. Significantly (P < 0.05) better FCR (2.21) was obtained in MS treatment. The final weight, weight gain and specific growth were similar (P> 0.05) among the five treatments. Higher gross return, net return and benefit-cost ratio were obtained in MS group than WB, MO and PKE. Significantly (P < 0.05) the highest lipid (1.97 % dry weight) was obtained in MS bioflocs and followed by RF, WB, MO and PKE bioflocs, respectively. The present study indicated that MS carbon source for biofloc technology enhanced M. rosenbergii postlarval survival and growth.

Distribution of the giant river prawn Macrobrachium rosenbergii (De Man, 1879) in Brazil: 43 years after its introduction

Abstract Macrobrachium rosenbergii (De Man, 1879) is a freshwater prawn from Malaysia and in 1977 it was introduced in Brazil for development of carciniculture. However, this species is currently found in various natural environments in the Brazilian states. The present study aimed at conducting a survey of M. rosenbergii sites in the natural environment, and shrimp farming ponds using this species. To do so, a search was conducted in scientific articles and databases on the occurrence of the species in Brazil. We found reports in 80 different sites in Brazil. Macrobrachium rosenbergii was found in the natural environment in eight states and 43 cities, with the largest amount of reports being from the states of Para and Maranhao. In addition, we found 28 reports in 13 states of shrimp farming ponds. Macrobrachium rosenbergii was not reported in natural environments in the Center-West region (except in state of Goias) and North region (except in state of Para). Moreover, we found that most of the M. rosenbergii reports were in temperature equal to or greater than 25 °C. Therefore, this species has expanded its area of occurrence throughout various Brazilian states, and we believe that this expansion may be greater than that reported in the current study.

Molecular characterization and expression dynamics of three key genes in the PI3K-AKT pathway reveal its involvement in the immunotoxicological responses of the giant river prawn Macrobrachium rosenbergii to acute ammonia and nitrite stress

Ammonia nitrogen and nitrite are two common forms of environmental toxicants for aquatic organisms including crustaceans. The PI3K-AKT pathway is an important intracellular signaling pathway related to cellular stress response, but involvement of this pathway in the immunotoxicological response of decapod crustaceans to aquatic toxicants such as ammonia nitrogen and nitrite still remains enigmatic. In this study, based on transcriptome mining and molecular cloning techniques, three key genes (named as MrPI3K, MrAKT and MrFoxO) in the PI3K-AKT signaling pathway were identified from the giant river prawn Macrobrachium rosenbergii. Sequence homology and phylogenetic analysis revealed that all the three genes harbored signature sequences of corresponding protein families, and shared high levels of similarities with their respective homologs from other species. MrPI3K, MrAKT and MrFoxO all displayed ubiquitous tissue distribution profiles, but their expression levels varied to a great extend among different tissues and between sexes. Following exposure to nitrite (20 mg/L nitrite-N) or ammonia (25 mg/L total ammonia-N) stresses for 24 h and 48 h, the three genes all responded by altering their expression levels at different time points, but they didn’t show uniform expression patterns following these stresses, indicating the diversified roles of these genes in different tissues and the complexity of this signaling pathway. Remarkably, MrPI3K and MrAKT were induced only in the hemocytes and intestine, respectively, indicating their specific roles in these organs. Our study demonstrated the potential utility of these genes as biomarkers of acute ammonia or nitrite toxicity in prawns, and also provided evidence that the PI3K-AKT pathway is involved in the immunotoxicological responses to nitrite and ammonia stress in M. rosenbergii.

A Kruppel-like factor from Macrobrachium rosenbergii (MrKLF) involved in innate immunity against pathogen infection

Kruppel-like factors (KLFs) belong to a family of zinc finger-containing transcription factors that are widely present in eukaryotes. In the present study, a novel KLF from the giant river prawn Macrobrachium rosenbergii (designated as MrKLF) was successfully cloned and characterized. The full-length cDNA of MrKLF was 1799 bp with an open reading frame of 1332 bp that encodes a putative protein of 444 amino acids, including three conserved ZnF_C2H2 domains at the C-terminus. Multiple alignment analysis showed that MrKLF and other crustacean KLFs shared high similarity. Quantitative real-time PCR analysis revealed that MrKLF mRNA was found in different tissues of prawns and detected in the gills, hepatopancreas, and intestines. After the challenge with Vibrio parahaemolyticus and Aeromonas hydrophila, different expression patterns of MrKLF in the gills, intestines, and hepatopancreas were observed. RNA interference analysis indicated that MrKLF was involved in regulating the expression of four antimicrobial peptides, namely, Crustin (Crus) 2, Crus8, anti-lipopolysaccharide factor (ALF) 1, and ALF3. These results help promote research on M. rosenbergii innate immunity.

Molecular and functional analyses of novel anti-lipopolysaccharide factors in giant river prawn (Macrobrachium rosenbergii, De Man) and their expression responses under pathogen and temperature exposure

Anti-lipopolysaccharide factor (ALF) is an immune-related protein that is crucially involved in immune defense mechanisms against invading pathogens in crustaceans. In the current study, three different ALFs of giant river prawn (Mr-ALF3, Mr-ALF8 and Mr-ALF9) were discovered. Based on sequence analysis, Mr-ALF3 and Mr-ALF9 were identified as new members of ALFs in crustaceans (groups F and G, respectively). Structurally, each newly identified Mr-ALF contained three α-helices packed against a four-stranded β-sheet bearing the LPS-binding motif, which usually binds to the cell wall components of bacteria. Tissue expression analysis using quantitative real-time RT-PCR (qRT-PCR) demonstrated that Mr-ALF3 was expressed in most tissues, and the highest expression was in the heart and hemocytes. The Mr-ALF8 gene was highly expressed in the heart, hemocytes, midgut, hepatopacreas and hindgut, respectively, while the Mr-ALF9 gene was modestly expressed in the heart and hemocytes, respectively. The transcriptional responses of the Mr-ALFs to Aeromonas hydrophila and hot/cold temperatures were investigated by qRT-PCR in the gills, hepatopancreas and hemocytes. We found that all Mr-ALFs were clearly suppressed in all tested tissues when the experimental prawns were exposed to extreme temperatures (25 and 35 °C). Moreover, the expression levels of these genes were significantly induced in all examined tissues by 2 different concentrations of A. hydrophila (1 × 106 and 1 × 109 CFU/ml), particularly 12 and 96 h after the injection. Finally, binding activity analysis of LPS-motif peptides of each Mr-ALF revealed that the LPS peptide of Mr-ALF3 exhibited the strongest adhesion to two pathogenic Gram-negative bacteria, A. hydrophila and Vibrio harveyi, and the non-pathogenic Gram-positive Bacillus megaterium. The results also showed that the Mr-ALF8 and Mr-ALF9 peptides had mild antimicrobial effects against similar tested bacteria. Based on information obtained in this study, novel ALF genes were clearly identified. Analyses of their responses under pathogenic and temperature stresses demonstrated the binding and antimicrobial activities of these ALFs and the consequent physiological effects, indicating their crucial functional roles in the prawn immune system.

Distinctive histopathology of Spiroplasma eriocheiris infection in the giant river prawn Macrobrachium rosenbergii

Spiroplasma eriocheiris was first named as the cause of tremor disease in the Chinese mitten crab Eriocheir sinensis in China in 2003. It was subsequently reported from China to infect also the crayfish Procambarus clarkii, the giant river prawn Macrobrachium rosenbergii, the oriental prawn Macrobrachium nipponensis and the whiteleg shrimp Penaeus vannamei. Unfortunately, none of these publications give clear pictures of the histopathology caused by the pathogen, even though this is one of the first diagnostic procedures often performed for newly reported diseases. Here we describe distinctive histological lesions caused in the hepatopancreatic tissue of M. rosenbergii infected with S. eriocheiris. In the hepatopancreas (HP), these consist of basophilic or mixed basophilic/eosinophilic lesions in cells confined to the interstitial spaces of the HP and not involving the hepatopancreatic tubule epithelial cells. Examination of the lesions by transmission electron microscopy revealed the presence of colonies of intracellular, un-walled bacterial cells of variable shape (but many crescent shaped) and approximately 150 nm in diameter. PCR using group-specific primers for the SSU rRNA followed by cloning and sequencing revealed 99.9% sequence identity to the matching sequence of S. eriocheiris. PCR tests for presence of S. eriocheiris in hepatopancreatic tissue samples gave positive test results, and in situ hybridization assays using a probe derived from the PCR product gave positive signals in the interstitial spaces of the HP, corresponding to the regions of the distinctive histological lesions. Less severe lesions containing cells with eosinophilic/basophilic inclusions were also found and confirmed by in situ hybridization in heart muscle, skeletal muscle, gills, connective tissue and the ventral nerve cord. Recognition of the distinctive histological lesions in interstitial spaces of the hepatopancreatic tissue of M. rosenbergii by histological analysis can be used as a strong presumptive indication of infection by S. eriocheiris and may help in the control of this rapidly-spreading, emerging pathogen.

Bioinformatics characterization of a cathepsin B transcript from the giant river prawn, Macrobrachium rosenbergii: Homology modeling and expression analysis after Aeromonas hydrophila infection.

Cathepsin B is a lysosomal proteolytic enzyme that has been suggested to play a role in pathological processes of immune system. In this study, the full-length cDNA sequence of cathepsin B transcript in the giant river prawn Macrobrachium rosenbergii (MrCTSB) was obtained from 454 pyrosequencing of cDNAs from hepatopancreas and muscle. It was 1158 bp in length, containing an open reading frame (ORF) of 987 bp corresponding to 328 amino acids. The predicted molecular mass and pI of MrCTSB protein was 36.04 kDa and 4.73. The major characteristics of MrCTSB protein consisted of a propeptide of C1 peptidase family at the N-terminus and a cysteine protease (Pept_C1) domain at the C-terminus. The 3-dimentional structure of MrCTSB was constructed by computer-assisted homology modeling. The folding of MrCTSB was highly conserved to human CTSB structure and the modeled MrCTSB displayed characteristics of cysteine proteinases superfamily. The docking study was performed to investigate binding interactions between known inhibitors against MrCTSB. Known inhibitors were oriented in the groove of catalytic site cleft. They bound to subsites from S2, S1, S1', and S2', respectively, with key residues in each subsite. Challenge of juvenile prawns with Aeromonas hydrophila revealed that the MrCTSB transcript in hepatopancreas significantly increased at 60-96 h post injection (hpi). This suggested that MrCTSB may play roles in innate immunity of M. rosenbergii. Our results provide useful information for a more comprehensive study in immune-related functions of MrCTSB.

Characterization, homology modeling and expression of the putative translationally controlled tumor protein gene from giant river prawn Macrobrachium rosenbergii (de Man)

The translationally controlled tumor protein (TCTP) is a multifunctional protein that promotes cell growth and viability. The TCTP has been associated with shrimp immune response by high levels being detected during the onset of white spot syndrome virus (WSSV) infection. The present study characterized the putative TCTP gene from the giant river prawn M. rosenbergii and investigated a putative function of this protein in response to Aeromonas hydrophila injection. A full-length cDNA sequence was obtained by assembly of short reads of RNA sequences from a 454-transcriptome dataset of river prawns and was designated as putative MrTCTP. The three-dimensional (3D) structure of MrTCTP was constructed using a homology modeling approach to predict the functional properties of the protein. Expression of MrTCTP was assessed in hepatopancreas tissues 96 h after injection using quantitative real-time polymerase chain reaction. The 704 bp full length cDNA of MrTCTP contained an open reading frame of 507 bp encoding a polypeptide of 168 amino acid residues. The conserved signature sequences of TCTP, I45-D55 and F123Y145 shared 61–92.3% similarity with the previously identified TCTP. The quality assessment and parameter validation indicated that the putative MrTCTP modeled structure was reliable. Expression levels of MrTCTP were significantly different (p < 0.05) between the control and infected prawns during 16–48 h. Transcript levels significantly increased 1.21-fold at 16 h to 2.26-fold at 48 h. The results suggested that the putative MrTCTP may be involved in the anti-apoptotic mechanism of river prawn.

Construction of an infectious Macrobrachium rosenbergii nodavirus from cDNA clones in Sf9 cells and improved recovery of viral RNA with AZT treatment

Macrobrachium rosenbergii nodavirus (MrNV) is usually accompanied by extra small virus (XSV) in natural outbreaks of white tail disease (WTD) in the giant river prawn Macrobrachium rosenbergii. Testing the virulence of MrNV alone has been problematic due to the difficulty in completely separating XSV from MrNV by viral purification steps from naturally infected shrimp. However, based on reports of natural M. rosenbergii specimens from WTD outbreak ponds that were positive for MrNV but negative for XSV led us to hypothesize that MrNV alone might cause WTD. To test this hypothesis, we prepared the two, complete genomic RNA fragments (RNA1 and RNA2) of MrNV from cDNA clones and used these to transfect Sf9 cells that subsequently showed cellular changes, including cell swelling, syncytial cell formation, and development of cytoplasmic inclusions within 72h post-transfection. Replication of RNA1 and RNA2 increased in the transfected cells and transmission electron microscopy of the cell lysates revealed the presence of icosahedral viral-like particles that were 40–50nm in diameter. When naïve Sf9 cells were inoculated with the cell lysate, the newly infected cells showed cellular changes and produced strong immunoreactivity against MrNV capsid protein indicating the infectious nature of the cell lysate. When the lysates were injected into the whiteleg shrimp Penaeus vannamei, MrNV RNA replication in the shrimp was followed by morality accompanied by typical MrNV lesions that gave possible positive immunohistochemical reactions for the MrNV capsid protein. Treatment of the Sf9 cells with azidothymidine triphosphate (AZT) prior to transfection significantly increased viral RNA synthesis and pathogenicity when compared with untreated, transfected cells. Using this model to produce infectious MrNV without XSV contamination proves that MrNV alone can be lethal to shrimp and it opens the way to further investigate the molecular basis of MrNV pathogenesis, and to develop antiviral strategy to control white tail disease.

Effects of arachidonic acid supplementation in maturation diet on female reproductive performance and larval quality of giant river prawn (Macrobrachium rosenbergii).

The giant river prawn (Macrobrachium rosenbergii) is one of the most farmed freshwater crustaceans in the world. Its global production has been stalling in the past decade due to the inconsistent quality of broodstock and hatchery-produced seeds. A better understanding of the role of nutrition in maturation diets will help overcome some of the production challenges. Arachidonic acid (20:4 n-6, ARA) is a fatty acid precursor of signaling molecules important for crustacean reproduction, prostaglandins E and F of the series II (PGE2 and PGF2α), and is often lacking in maturation diets of shrimp and prawns. We examined the effects of ARA in a combination of different fish oil (FO) and soybean oil (SO) blends on females’ reproductive performance and larval quality. Adult females (15.22 ± 0.13 g and 11.12 ± 0.09 cm) were fed six isonitrogenous and isolipidic diets containing one of two different base compositions (A or B), supplemented with one of three levels of Mortierella alpine-derived ARA (containing 40% active ARA): 0, 1 or 2% by ingredient weight. The two base diets differed in the percentages of (FO and SO with diet A containing 2% SO and 2% FO and diet B containing 2.5% SO and 1.5% FO, resulting in differences in proportional contents of dietary linoleic acid (18:2n-6, LOA) and docosahexaenoic acid (22:6n-3, DHA)). After the eight-week experiment, prawns fed diet B with 1 and 2% ARA supplement (B1 and B2) exhibited the highest gonadosomatic index (GSI), hepatosomatic index (HSI), egg clutch weight, fecundity, hatching rate, number of larvae, and reproductive effort compared to those fed other diets (p ≤ 0.05). Larvae from these two dietary treatments also had higher tolerance to low salinity (2 ppt). The maturation period was not significantly different among most treatments (p ≥ 0.05). ARA supplementation, regardless of the base diet, significantly improved GSI, HSI, egg clutch weight and fecundity. However, the diets with an enhanced ARA and LOA (B1 and B2) resulted in the best reproductive performance, egg hatchability and larval tolerance to low salinity. These dietary treatments also allow for effective accumulation of ARA and an n-3 lcPUFA, DHA in eggs and larvae.

Isolation of AHL-degrading bacteria from micro-algal cultures and their impact on algal growth and on virulence of Vibrio campbellii to prawn larvae.

Inactivation of quorum sensing (QS) signal molecules, such as acylhomoserine lactones (AHLs) of pathogenic bacteria, has been proposed as a novel method to combat bacterial diseases in aquaculture. Despite the importance of micro-algae for aquaculture, AHL degradation by bacteria associated with micro-algal cultures has thus far not been investigated. In this study, we isolated Pseudomonas sp. NFMI-T and Bacillus sp. NFMI-C from open cultures of the micro-algae Tetraselmis suecica and Chaetoceros muelleri, respectively. An AHL degradation assay showed that either monocultures or co-cultures of the isolates were able to degrade the AHL N-hexanoyl-L-homoserine lactone. In contrast, only Bacillus sp. NFMI-C was able to inactivate N-hydroxybutanoyl-L-homoserine lactone, the AHL produced by Vibrio campbellii. The isolated bacteria were able to persist for up to 3weeks in conventionalized micro-algal cultures, indicating that they were able to establish and maintain themselves within open algal cultures. Using gnotobiotic algal cultures, we found that the isolates did not affect growth of the micro-algae from which they were isolated, whereas a mixture of both isolates increased the growth of Tetraselmis and decreased the growth of Chaetoceros. Finally, addition of Bacillus sp. NFMI-C to the rearing water of giant river prawn (Macrobrachium rosenbergii) larvae significantly improved survival of the larvae when challenged with pathogenic V. campbellii, whereas it had no effect on larval growth.

Ontogenetic Development of Sensory Structures on the Antennules and Antennae of the Giant River PrawnMacrobrachium rosenbergii(De Man)

In this study the occurrence of sensory structures on the antennules and antennae of the giant river prawn Macrobrachium rosenbergii (De Man) during postembryonic ontogenetic development were examined. Larvae and postlarvae were obtained from hatchery recirculating tanks, juveniles from indoor nursery tanks, and adults from earthen grow-out ponds. The animals were fixed with Karnovsky fixative and dissected. Antennules and antennae were removed, metal-coated, and photodocumented using a scanning electron microscope. The antennules have aesthetascs and simple plumose and pappose setae; the antennae have simple, plumose and pappose setae. These structures increase in density, covered surface, and distribution during ontogeny and should be related to chemoreception and mechanoreception. The antennular statocyst that appears during larval stage VII of the giant river prawn has an array of sensory structures that enable the perception of chemical and tactile stimuli beginning with its early life stages. The ontogenetic changes observed allow an inference that initial-stage larvae, advance-stage larvae, juveniles, and adults have different capacities to exploit the environment.

Treatment efficiency of effluent prawn culture by wetland with floating aquatic macrophytes arranged in series.

The efficiency of a series of wetland colonized with Eichhornia crassipes and Salvinia molesta to treat the effluent of a giant river prawn (Macrobrachium rosenbergii) broodstock pond was evaluated in this study. The experimental design was completely randomized and was performed in 9 rectangular tanks (1.6 m3) with three treatments (constructed wetlands) and three replicates. The treatment types included: a wetland colonized with E. crassipes and S. molesta (EcSm) arranged sequentially, a wetland with E. crassipes only (Ec) and a wetland with S. molesta only (Sm). The means of suspended particulate material (SPM), total inorganic nitrogen (TIN), total Kjeldahl nitrogen (TKN), P-orthophosphate (PO4-P) and total phosphorus (TP) of the treated effluents were compared using ANOVA followed by Tukey's test (P<0.05). The effluent treated in Ec and EcSm wetlands exhibited lower SPM concentrations. The Ec wetland reduced TIN, TKN, PO4-P and TP by 46.0, 43.7, 44.4 and 43.6%, respectively. In the EcSm wetland, the reduction of TIN (23.0%), TKN (33.7%) and PO4-P (26.7%) was similar to the Sm wetland (19.8% TIN, 30.9% TKN and 23.8% PO4-P). The Ec wetland was more efficient in treating pond effluent due likely to the higher root surface of E. crassipes, which forms an extensive area favorable to retention and adsorption of debris and absorption of nutrients.

The Apparent Quorum-Sensing Inhibitory Activity of Pyrogallol Is a Side Effect of Peroxide Production

There currently is more and more interest in the use of natural products, such as tea polyphenols, as therapeutic agents. The polyphenol compound pyrogallol has been reported before to inhibit quorum-sensing-regulated bioluminescence in Vibrio harveyi. Here, we report that the addition of 10 mg · liter(-1) pyrogallol protects both brine shrimp (Artemia franciscana) and giant river prawn (Macrobrachium rosenbergii) larvae from pathogenic Vibrio harveyi, whereas the compound showed relatively low toxicity (therapeutic index of 10). We further demonstrate that the apparent quorum-sensing-disrupting activity is a side effect of the peroxide-producing activity of this compound rather than true quorum-sensing inhibition. Our results emphasize that verification of minor toxic effects by using sensitive methods and the use of appropriate controls are essential when characterizing compounds as being able to disrupt quorum sensing.