Prawn Tissues Research Articles

Superoxide dismutase activity in tissues of juvenile cauque river prawn (Macrobrachium americanum Bate, 1868) fed with different levels of protein and lipid

The effect of different proteins and lipids levels on antioxidant response of superoxide dismutase (SOD) was tested in muscle, hepatopancreas and whole-body tissues of cauque river prawn Macrobrachium americanum juvenile. Six diets with two crude protein (35 and 40% diet) and three lipid levels (6, 10, and 14% diet) were tested for juveniles in a factorial manner (3×2), to provide six different dietary. Juvenile prawns (0.22 ± 0.03 g) were randomly placed in 18 plastic tanks (160 L), at a density of 15 juveniles per tank (3 tank replicates/treatment). The assay lasted 60 days. SOD activity was significantly different in muscle, hepatopancreas and whole body depending on proteins and lipids levels in the diet. Results indicate that the diet containing 35% protein and 10% lipid provided adequately to while preventing diet-induced oxidative stress and protecting the integrity of the antioxidant response of SOD.

Wntless, a conserved Wnt-transport protein, is involved in the innate immune response of Macrobrachium rosenbergii

Wnt signaling plays important roles in a variety of developmental and pathological processes. Here we show that Wntless, the main regulator for Wnt secretion, is involved in the innate immune response of the giant freshwater prawn, Macrobrachium rosenbergii. The full-length cDNA of the prawn Wntless (named MrWntless) is 2173 bp in length and contains a 1602-bp open reading frame (ORF), which is conceptually translated into a 533-amino acids sequence. MrWntless protein contains a highly conserved Wnt-binding domain which is required for secretion of Wnt ligands, and exhibits 57–67% identity with known Wntless proteins of other animals. MrWntless was found to be expressed in a variety of prawn tissues including heart, gill, muscle, gut, hepatopancreas and ovary. Moreover, MrWntless expression was significantly increased in the hepatopancreas and gill of the prawns challenged by the bacterial pathogen Aeromonas hydrophila and Vibrio parahaemolyticus. Knockdown of MrWntless by RNA interference in prawns led to dramatically decreased MrWntless expression of approximately 70%. Furthermore, the cumulative mortality rate of the prawn injected with MrWntless dsRNA was greatly increased in response to A. hydrophila challenge compared with the control prawns. Taken together, we provide evidence that prawn Wntless is important for their innate immune response against bacterial pathogens.

Heavy Metal Levels in some Edible Crustacean and Mollusk Species Marketed in Mersin

Muscle tissues of squid (Loligo vulgaris), cuttlefish (Sepia officinalis) and prawn (Penaeus semisulcatus) marketed for consumption were analyzed for their Fe, Cu, Zn, Cd and Pb levels. Metal analysis were carried out using Inductively Coupled Plasma-Mass Spectroscopic (ICP-MS) methods. Muscle levels of Fe, Cu, Zn and Pb ranged between 0.50–19.82, 0.53–8.57, 6.80–32.12 and <0.003–1.60 mg/kg w.w., respectively whereas Cd level was below detection limits in the species studied. Mean muscle levels of metals in samples for consumption were compared with provisional tolerable daily (PTDs) and weekly (PTWs) limits. It was shown that the levels of metals in tissues analyzed were below PTDs and PTWs. Mean metal levels of all samples were also below the upper limits set by Turkish Food Codex (TFC) and European Union (EU) Commission. Hence it was shown that levels of the selected 5 metals in muscle tissues of squid, cuttlefish and prawns marketed in Mersin were in accordance with the quality standards set by TFC and EUC and concluded that they do not pose any health problems for human consumption.

Exploring the antivirulent and sea food preservation efficacy of essential oil combined with DNase on Vibrio parahaemolyticus

Vibrio parahaemolyticus is a predominant aquaculture pathogen causing food borne infections through the consumption of raw or undercooked sea foods. Biofilm formation and quorum sensing mediated virulence factors play a pivotal role in mediating these infections. The present study evaluates the antibiofilm and anti-quorum sensing potential of an unexplored essential oil (EO) and its major compounds (cinnamaldehyde and linalool) against V. parahaemolyticus. Furthermore, the synergistic effects of the EO along with a commercial available DNase I and marine bacterial DNase (MBD) were explored for its antibiofilm efficacy. In addition, the food preservative efficacy of linalool and cinnamaldehyde were evaluated in prawns (a sea-food model) infected with V. parahaemolyticus stored at 28 °C and 4 °C. The treated prawns showed reduced bacterial load and exhibited minimum lipid peroxidation. Scanning Electron Microscopy (SEM) revealed the intact muscle tissues of the treated samples which indicate that the EO components did not damage the prawn tissues. The results revealed that the individual EO components has good efficacy equal to that of the standard food preservative sodium benzoate. This study shows that the synergistic action of EO and DNases might offer an alternate strategy for sea food preservation.

Microplastics in different tissues of fish and prawn from the Musa Estuary, Persian Gulf

Commercially-important species of fish and a crustacean from four sites in the Musa estuary and a site in the Persian Gulf have been analysed for the presence and location of microplastics (MPs). A total of 828 MPs were detected in the guts (gastrointestinal tracts), skin, muscle, gills and liver of demersal and pelagic fish (Platycephalus indicus, Saurida tumbil, Sillago sihama, Cynoglossus abbreviatus) from all five sites and in the exoskeleton and muscle of the tiger prawn, Penaeus semisulcatus, from three sites. On an individual basis, MPs were most abundant in P. indicus (mean = 21.8) and least frequently encountered in P. semisulcatus (mean = 7.8), but when normalized on a mass basis, MPs ranged from 0.16 g-1 for C. abbreviatus to 1.5 g-1 for P. semisulcatus. Microscopic analyses (polarized light, fluorescence, SEM/EDS) revealed that MPs were mainly fibrous fragments (with a few angular fragments) of various colour and size (<100 μm to > 1000 μm) and with strong C and O signatures. Additional particles detected that were distinctly different in colour, morphology, brittleness and elemental composition (part-metallic, and containing Cu) were suspected of being fragments of antifouling paint. The means of entry of MPs into tissues not involved in digestion are unclear but could be related to translocation or adherence. Regardless of the mode of accumulation, the presence of MPs in heavily fished species of fish and crustacean raises concerns about the potential transfer of synthetic materials into humans.

Impact of heavy metal bioaccumulation on antioxidant activities and DNA profile in two earthworm species and freshwater prawn from Ogun River

The use of freshwater invertebrates as bioindicator of heavy metal pollution is an important tool for environmental biomonitoring. This study investigated antioxidant activities and DNA profile in two limicolous earthworms (Alma millsoni and Libyodrilus violaceus) and freshwater prawns (Macrobrachium vollenhovenii) at selected points of Ogun River, Abeokuta. Heavy metal concentrations and DNA profile in the earthworms and prawn tissues were measured using standard procedures. Zn concentration was higher than other heavy metals in A. millsoni (685.83±114.42mg/kg), L. violaceus (1913.3±1098.7mg/kg) and M. vollenhovenii (134.7±13.61mg/kg). Superoxide dismutase activity ranged from 62.44±7.16–79.82±11.18U/g tissues, 60.26±11.18–71.07±7.54U/g tissues and 74.07±16.69–87.79±8.50U/g tissues in A. millsoni, L. violaceus and M. vollenhovenii respectively. RAPD-PCR revealed varying DNA profile among the earthworms samples; the UPGMA dendrogram formed two distinct clusters at genetic similarity coefficient of 0.15–0.2 with one cluster consisting of Alma millsoni and Libyodrilus violaceus from Sokori, Enugada and Iberekodo sampling points and the second cluster forming two distinct sub-clusters comprising Arakanga and Ago-ika's L. violaceus in one and A. millsoni in the other. High genetic variability was recorded among the earthworm species while the freshwater prawn showed no variability. Antioxidant activities and genetic variability in earthworms could serve as biomarkers of heavy metal pollution in freshwater environment.

Leptin-like immunoreactivity in the central nervous system, digestive organs, and gonads of the giant freshwater prawn, Macrobrachium rosenbergii

Leptin, a highly conserved adipocyte-derived hormone, plays important roles in a variety of physiological processes, including the control of fat storage and metabolic status which are linked to food intake, energy homeostasis, and reproduction in all vertebrates. In the present study, we hypothesize that leptin is also present in various organs of the fresh water prawns, Macrobrachium rosenbergii. The existence and distribution of a leptin-like peptide in prawn tissues were verified by using Western blotting (WB) and immunohistochemical detection (ID) using primary antibody against human leptin. With WB, a leptin-like peptide, having a molecular weight of 15kDa, was detected in the brain, thoracic ganglia, abdominal ganglia, parts of the gastro-intestinal tract, hepatopancreas, adipocytes and gonads. By ID, leptin immunoreactivity (leptin-ir) was detected in the brain, thoracic ganglia and intersegmental commissural nerve fibers of abdominal ganglia. In the gastrointestinal tract, there was intense leptin-ir in the apical part of the epithelial cells of the cardiac and pyloric parts of the stomach. In the midgut and hindgut, the leptin-ir was detected in epithelial cells and basal cells located near the basal lamina of the epithelium. In addition, there was leptin-ir in the Restzellen cells in the hepatopancreas which produce digestive enzymes. In the ovary, the strong intensity of a leptin-ir was detected in the cytoplasm of middle to late stage oocytes, whereas no positive staining was detected in follicular cells. An intense leptin-ir was detected in spermatocytes and sustentacular cells in the seminiferous tubules in the testes of small and orange claw males. Taken together, the detection of the leptin-ir in several organs implicates the existence of a leptin-like peptide in various organs of the freshwater prawn; and like in vertebrates this peptide may be an important hormonal factor in controlling feeding and reproductive process.

Parasitic Helminth Fauna and Heavy Metals Analysis in Macrobrachium macrobranchion (Herklots, 1851) and Macrobrachium vollenhovenii (Herklots, 1857) From Lekki Lagoon, Lagos, Nigeria.

This study was carried out to investigate the uptake and bioaccumulation of heavy metals by intestinal helminths parasites in relation to the muscular tissues of the freshwater prawn (Macrobrachium species) obtained from Lekki Lagoon, Epe, Lagos, Nigeria. A total of 120 specimens composed of 82 Macrobrachium macrobrachion and 38 Macrobrachium species was Zn> Fe> Cu> Pb> Cr> Cd> Ni and Mn> Fe> Zn> Cr> Pb> Cu> Ni> Cd in the parasite.In the the non –infected specimens the trend shows; Mn > Fe> Cu> Zn> Cd> Cr, Ni> and Pb. Manganese (Mn) was found to have high concentration compared to other metal analysed .Two of the metals (Pb and Mn) were found in significantly higher concentrations vollenhovenii were examined for helminths parasites. Four species of helminths parasites were recovered; Procamallanus species, Cucullanus species, Anisakis species and Pomphorhynchus species. Out of 82 specimens of Macrobrachium macrobrachion examined, 16 (19.51%) were infected. These infected specimens had 16(19.51%) males and 0(0.00%) female while the non- infected individuals had 49 (59.76%) male and 17(20.73%) females. The Chi-square distribution was significant at 0.01 level (x2(2) =5.20, p< 0.01).Sixteen specimens (16) (42.11%) were infected out of the 38 Macrobrachium vollenhovenii examined. The infected Macrobrachium vollenhovenii had 16(42.11%) males and 0(0.00%) female and the non- infected individuals had 18(47.37%) males and 4(10.53%) females. The Chi-square distribution was significant at 0.01 level (x2(2) =5.20, p< 0.01). The condition factor in the study for Macrobrachium macrobrachion in female was 1.4±0.40 and in male 1.45±0.49, while the condition factor (K) of M. vollenhovenii in female was 1.18±0.20 and in male 1.63±0.61. The mean value for the condition factor of both in acanthocephalans compared with the host tissues. While five of the metals (Fe, Zn, Cd, Cu and Cr) were found in significant high concentration in the infected tissue than the parasites. Analysis of all the heavy metal sample recorded for the water and sediment media of Lekki lagoon, indicate Zn to be above the FME permissible limit. However, findings from this study indicate that the acanthocephalans interfere with the uptake and bioaccumulation of heavy metal in relation to the tissue of the freshwater prawn, and can be applied in biomonitoring procedure of environmental pollution.

Effects of alternative oil sources in feed on growth and fatty acid composition of juvenile giant river prawn (Macrobrachium rosenbergii)

To relieve the pressure on the future use of fish oil (FO), alternative oil sources need to be explored. Alternative oil sources were evaluated—Schizochytrium sp. (SZ) and soybean oil (SO)—on the growth performance and flesh quality of juvenile river prawn, Macrobrachium rosenbergii. Five experimental diets differed in the types of oil used (oil comprised 3% of dietary ingredients): 3% FO, 1% SZ + 2% SO, 1.5% SZ + 1.5% SO, 2% SZ +1% SO and 3% SZ. After 60 d of the experiment, the survival rates of prawns fed non-FO diets did not significantly (p > 0.05) differ from those fed the FO diet (77.82 ± 4.45–93.38 ± 0.00%). Moreover, prawns fed diets containing both SZ and SO had significantly (p < 0.05) better growth performance than those fed a single oil source. Prawns fed 2% SZ+1% SO showed the best final weight, percentage weight gain, absolute daily weight gain, specific growth rate and feed conversion ratio (p < 0.05) while those fed 1.5% SZ +1.5% SO or 3% SZ had the highest survival. Tissues of prawns fed the non-FO diets contained higher amounts of n−6 polyunsaturated fatty acid (PUFA) but were lower in n−3 long-chain PUFAs (eicosapentaenoic acid and docosahexaenoic acid) than those fed the FO diet. Among the non-FO groups, prawns fed 3% SZ had the most similar flesh fatty acid profile to those fed 3% FO. Substitution of FO with combinations of SZ and SO significantly improved growth performance and feed utilization. The study recommended diets containing 2% SZ + 1% SO or 1.5% SZ + 1.5% SO for M. rosenbergii juveniles.

Vitellogenin and vitellogenin receptor gene expression and 20-hydroxyecdysone concentration in Macrobrachium rosenbergii exposed to chlordecone.

Chlordecone is a persistent organochlorine pesticide widely used in Guadeloupe (French West Indies) to control the banana weevil Cosmopolites sordidus. Although it was previously highlighted that chlordecone may affect the reproduction and growth of vertebrate species, little information is available on the chlordecone effects in invertebrates. The present study investigated the effects of chlordecone on a hormone and a protein having key roles in reproduction and growth of the decapod crustacean Macrobrachium rosenbergii, by measuring the 20-hydroxyecdysone concentration, vitellogenin, and vitellogenin receptor gene expression, as well as the bioconcentration of chlordecone in exposed prawns. First, the results revealed that chlordecone was accumulated in M. rosenbergii. Then, it was found that Vg and VgR gene expression were increased in male and female M. rosenbergii exposed to chlordecone for 90 and 240days, while the 20-hydroxyecdysone concentrations were decreased. This work suggests that chlordecone accumulates in prawn tissues and could affect key molecules involved in the reproduction and the growth of the invertebrate M. rosenbergii. However, many questions remain unresolved regarding the impacts of chlordecone on growth and reproduction and the signaling pathways responsible for these effects, as well as the potential role of confounding factors present in in situ studies.

Single CRD containing lectin from Macrobrachium rosenbergii (MrLec) participates in innate immunity against pathogen infections.

As a type of pattern-recognition proteins, lectins perform important functions in the innate immunity of crustaceans, including prawns. Although several reports showed that C-type lectin domain family (CLEC) importantly functions in host-pathogen interactions, limited research has focused on CLEC in Macrobrachium rosenbergii. In the present study, a new single CRD containing CLEC (designated as MrLec) was reported in freshwater prawns, M.rosenbergii. The full-length cDNA of MrLec consisted of 1027bp with an open reading frame of 801bp, which encoded a peptide of 266 amino acid residues. Genomic sequence for MrLec was also obtained from the M.rosenbergii, which contain 4 exons and 3 introns. MrLec was found to contain a single carbohydrate-recognition domain with an EPN motif. MrLec was ubiquitously distributed in various tissues of a normal prawn, particularly in the hepatopancreas and gills. MrLec expression in the gills was significantly upregulated after a challenge with Vibrio parahaemolyticus and downregulated at 24h after MrLec RNA interference (MrLec-RNAi). The expression levels of some AMPs, including antilipopolysaccharide factor 1 (Alf1) and lysozyme 2 (Lyso2), also markedly decreased after MrLec-RNAi. Recombinant MrLec can agglutinate (Ca(2+)-dependent) and bind both Gram-negative and Gram-positive bacteria. Results suggested that MrLec participates in the recognition of invading pathogens and functions in the immune response of prawn against pathogen infections.

Identification and comparative analysis of the oriental river prawn (Macrobrachium nipponense) microRNA expression profile during hypoxia using a deep sequencing approach

Hypoxia refers to a state of oxygen deficiency, which is observed frequently in aquaculture ponds. MicroRNAs (miRNAs) are small non-coding RNAs that are important effectors in regulating gene expression through posttranscriptional mechanisms. They are key elements in the response to hypoxia. The oriental river prawn (Macrobrachium nipponense) is an important commercial aquaculture species, and is sensitive to hypoxia. To date, there are no reports describing M. nipponense miRNAs. In this study, Solexa deep sequencing technology was used for high-throughput analysis of miRNAs in a small RNA library isolated from four M. nipponense tissues (gill, hepatopancreas, muscle and hemocytes). In total, 9,227,356 reads were obtained, 4,293,155 of which were related to 267 unique miRNAs, including 203 conserved and 64 prawn-specific miRNAs. Furthermore, miRNA features including length distribution and end variations were characterized. Annotation of targets revealed a broad range of biological processes and signal transduction pathways regulated by M. nipponense miRNAs. In addition, 880 co-expressed and 39 specific (25 normoxia-specific and 14 hypoxia-specific) miRNAs that may be involved in the response to hypoxia were confirmed using miRNA microarray analysis from the four prawn tissues combined. Real-time quantitative PCR (qPCR) analysis of eight miRNAs in the normoxia and hypoxia groups showed good concordance between the sequencing and qPCR data. This study provides the first large-scale identification and characterization of M. nipponense miRNAs and their potential targets, and represents a foundation for further characterization of their roles in the regulation of the diversity of hypoxia processes.

Developing immunological methods for detecting Macrobrachium rosenbergii nodavirus and extra small virus using a recombinant protein preparation.

Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV) have been identified as the causative agents for white tail disease (WTD) of M.rosenbergii. In this study, the gene sequences encoding MrNV and XSV capsid proteins were separately ligated into the pGEX-4T-3 expression vector and transformed into Escherichia coli. After induction, glutathione-S-transferase (GST)-tagged MrNV and XSV fusion proteins were obtained with molecular masses of 68 and 43 kDa, respectively. Specific polyclonal antibodies for MrNV and XSV against viral recombinant proteins and infected prawn tissues were verified using Western blotting. According to immunodot blot assay results, the detection sensitivities of antibodies were approximately 5ng μL(-1) for both recombinant proteins GST-MrNV and GST-XSV. In additional, MrNV and XSV were detected at dilution levels of 1:2560 and 1:640 in the infected prawn tissues, respectively. No cross-reactions with white spot syndrome virus or grouper nervous necrosis virus were observed using immunodot blot assays. MrNV and XSV in infected muscle tissues were detected using immunohistochemistry. Although the detection limit of the immunodot blot assay was lower than that of nested reverse transcription polymerase chain reaction, these polyclonal antibodies can be useful for confirming MrNV and XSV infections in field tests.

Identification of five anti-lipopolysaccharide factors in oriental river prawn, Macrobrachium nipponense.

Anti-lipopolysaccharide factors (ALFs) are a group of antimicrobial peptides (AMPs) with broad-spectrum antimicrobial activities and antiviral activities mainly found in crustaceans and horseshoe crabs. In the present study, we identified 5 ALF expression sequence tags (ESTs) through analysis of the established M. nipponense transcriptome, and cloned their full-length cDNA sequences using rapid amplification of cDNA ends (RACE) method. The 5 ALFs were designated as MnALF1-5, and all of them showed high similarity with their Macrobrachium rosenbergii homologs in the phylogenetic analyses, especially in LPS binding domains. In healthy adult prawns, we found the highest expression of MnALF2 and MnALF4 in haemocytes, and the highest expression of MnALF4 and MnALF3 in intestine. Some isoforms of MnALF were down-regulated but the majority was up-regulated in different prawn tissues upon Aeromonas hydrophila challenge. To conform the expected antimicrobial activities harbored in MnALFs' LPS binding domains, we used a synthesized peptide cMnALF24 that corresponds to the LPS binding domain of MnALF2 as a representative molecule for the antibacterial activity test, and found that cMnALF24 possessed strong and broad-spectrum antibacterial activity against Gram positive and Gram negative bacteria, but no inhibition activity against fungi; Meanwhile, in the hemolytic test, cMnALF24 showed weak hemolysis activities (around 10%) to the rabbit red blood cells at concentrations of 0.67-33.50 μM. This study provides insights into understanding the antibacterial function of ALFs in the innate immunity of freshwater prawn, and reports a peptide that can be a potential drug candidate with good efficacy against bacterial infection and low toxicity to host cells.

Transciptomic and histological analysis of hepatopancreas, muscle and gill tissues of oriental river prawn (Macrobrachium nipponense) in response to chronic hypoxia.

BackgroundOriental river prawn, Macrobrachium nipponense, is a commercially important species found in brackish and fresh waters throughout China. Chronic hypoxia is a major physiological challenge for prawns in culture, and the hepatopancreas, muscle and gill tissues play important roles in adaptive processes. However, the effects of dissolved oxygen availability on gene expression and physiological functions of those tissues of prawns are unknown. Adaptation to hypoxia is a complex process, to help us understand stress-sensing mechanism and ultimately permit selection for hypoxia- tolerant prawns, we performed transcriptomic analysis of juvenile M. nipponense hepatopancreas, gill and muscle tissues by RNA-Seq.ResultsApproximately 46,472,741; 52,773,612 and 58,195,908 raw sequence reads were generated from hepatopancreas, muscle and gill tissues, respectively. A total of 62,722 unigenes were generated, of the assembled unigenes, we identified 8,892 genes that were significantly up-regulated, while 5,760 genes were significantly down-regulated in response to chronic hypoxia. Genes from well known functional categories and signaling pathways associated with stress responses and adaptation to extreme environments were significantly enriched, including genes in the functional categories “response to stimulus”, “transferase activity” and “oxidoreductase activity”, and the signaling pathways “oxidative phosphorylation”, “glycolysis/gluconeogenesis” and “MAPK signaling”. The expression patterns of 18 DEGs involved in hypoxic regulation of M. nipponense were validated by quantitative real-time reverse-transcriptase polymerase chain reactions (qRT-PCR; average correlation coefficient = 0.94). In addition, the hepatopancreas and gills exhibited histological differences between hypoxia and normoxia groups. These structural alterations could affect the vital physiological functions of prawns in response to chronic hypoxia, which could adversely affect growth and survival of M. nipponense.ConclusionsGene expression changes in tissues from the oriental river prawn provide a preliminary basis to better understand the molecular responses of M. nipponense to chronic hypoxia. The differentially expressed genes (DEGs) identified in M. nipponense under hypoxia stress may be important for future genetic improvement of cultivated prawns or other crustaceans through transgenic approaches aimed at increasing hypoxia tolerance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1701-3) contains supplementary material, which is available to authorized users.

Preparation and characterisation of certified reference materials for furazolidone and nitrofurazone metabolites in prawn

Nitrofuran residues in food, particularly intensively farmed prawns, were identified as an important trade and health issue. No certified reference materials were available to allow laboratories to demonstrate satisfactory performance of their analytical methods. Freeze-dried prawn reference materials MX012A and MX012B were prepared at the National Measurement Institute, Australia, from blank and contaminated prawn tissue. A high-accuracy, exact-matching isotope dilution mass spectrometry method was developed for the analysis of two nitrofuran metabolites in the prawn materials. Residues were extracted by acid hydrolysis and derivatisation with 2-nitrobenzaldehyde, extracts were purified by liquid–liquid extraction followed by solid-phase extraction, and instrumental analysis was by ultra-high-pressure liquid chromatography with electrospray tandem mass spectrometry (UHPLC-ESI-MSMS). The method was used to certify the reference materials for mass fraction of 3-amino-2-oxazolidinone (AOZ) and semicarbazide (SEM), including the preparation of detailed measurement uncertainty budgets. MX012A contains AOZ at (137.5 ± 8.5) ng/g of freeze-dried material, and MX012B contains AOZ at (30.2 ± 1.8) ng/g and SEM (fortified) at (70.3 ± 3.1) ng/g. When reconstituted as directed on the certificate, the materials contain AOZ at (20.6 ± 1.3) ng/g and (4.53 ± 0.27) ng/g (MX012A and MX012B, respectively) and SEM at (10.5 ± 0.5) ng/g (MX012B). The individual components contributing to the measurement uncertainty estimates were the mass fractions assigned to calibration standards, gravimetric mass measurements, precision of the analytical method, reproducibility, long-term storage stability of the material at −20 °C, stability of the material during transportation, and potential bias due to extraction efficiency of the incurred analyte and matrix interference.

Evidence of rapid transfer and bioaccumulation of Microcystin‐ LR poses potential risk to freshwater prawn Macrobrachium rosenbergii (de Man)

Microcystins accumulate in aquatic organisms and can be transferred to higher trophic levels, eventually affecting vector animals and consumers. We examined three levels of an aquatic food chain (Microcystis aeruginosa, Daphnia magna and Macrobrachium rosenbergii) to identify the transfer efficiency and risk of microcystin on prawns. Samples were analysed using ultra performance liquid chromatography-mass spectrometry (MS)/MS and microcystin-LR (MC-LR) distributions in prawn tissues were studied. The results showed that prawns accumulate MC-LR both directly from M. aeruginosa and indirectly through D. magna which was pre-exposed to M. aeruginosa. MC-LR was detected in the gills, digestive tracts and hepatopancreas of the prawns 2 h after exposure. MC-LR accumulated in prawns to 0.49 ± 0.04 μg g−1 dry weight in hepatopancreas within 24 h, while it was not detected in muscle samples, and rarely appeared in blood samples in such a short period. Although MC-LR was not detected in muscle, the head including hepatopancreas of the prawns accumulated troublesome amounts of MC-LR. These results demonstrate that microcystis blooms in prawn farming potentially pose a risk to human consumers, although prawns may be exposed to the bloom for a very short time, hence regular monitoring of blue green algae population is recommended.

Metabolic, immune responses in prawn (Penaeus monodon) exposed to ambient ammonia

This article reports on the changes in the metabolic detoxification indices of the hepatopancreas, muscle, and gill tissues of juvenile prawn (body length of 5.0 ± 0.5 cm) of Penaeus monodon at different ammonia levels (at concentrations of 0, 10, 20, and 30 mg/L) as well as the immune-related gene expressions of the prawn under elevated ammonia (30 mg/L) stress. Results showed that glutamine synthetase (GS) activity and glutamine (Gln) content were higher in the muscle than those in the gill and hepatopancreas, not only at the normal level but also under stress. The GS activity and the Gln concentration at 96 h were significantly higher than those in the control group (p < 0.05) and positively correlated with the ammonia concentration from 0 to 48 h. The gene expressions of C-lysozyme, antibacterial peptide (crustin), and antilipopolysaccharide factor in P. monodon were upregulated at the initial period and downregulated at the later period under high ammonia stress (30 mg/L ammonia), except for the crustin gene in muscle, which maintained a continuous high expression from 0 to 96 h (p < 0.05). Our results confirmed that ammonia stress induced a detoxification metabolic pathway at least dependent on Gln synthesis in juvenile prawn. Body immunity was also activated at the initial period and decreased at the later period of high ammonia stress. Muscle is a sensitive tissue reflecting the ammonia stress state not only by physiological index but also by crustin mRNA level in juvenile prawn.

On the safety of RNAi usage in aquaculture: The case of all-male prawn stocks generated through manipulation of the insulin-like androgenic gland hormone

Abstract The recent introduction of RNA interference (RNAi) based biotechnology in aquaculture has aroused public awareness regarding safety aspects related to the use of such temporal transcript manipulation. In the present study, we demonstrate use of this biotechnology in large-scale production of all-male freshwater prawn Macrobrachium rosenbergii, relying on a two-phased approach. First, the insulin-like androgenic gland hormone (Mr-IAG) was silenced by dsRNA injections, causing sex-reversal of males into ‘neo-females’ (genetic males with female phenotype, with 86% success in this study). The next step involved mating the neo-females with normal males to produce all-male progeny. The administered exogenous dsRNA was fully cleared from the prawn's tissues after 7 days. Gene silencing through dsMr-IAG appeared to be temporary, with decay seen over time and nearly full expression of Mr-IAG (~ 82%) being restored after 28 days. Assessment of reproduction and fecundity in normal females versus neo-females revealed that in both groups, ~ 80% of the prawns were in a reproductive state and no significant difference was found in their reproductive output, either in terms of brood mass or number. Population structure, as indicated by the normal occurrence of male morphotypes, in both mixed-sex and all-male populations was examined in terms of weight and morphotype frequency distribution. The final harvest and marketing of the all-male prawn offspring occur about 19 months, i.e., one generation after the actual RNAi procedure. Thus, on top of the aquaculture yield advantage, the use of such RNAi procedure in crustacean aquaculture seems to be safe due to its temporary nature.

Metal accumulation in the greentail prawn, Metapenaeus bennettae, in Sydney and Port Hacking estuaries, Australia

Metal concentrations of the inshore greentail prawn, Metapenaeus bennettae, and surface sediments from locations within Sydney estuary and Port Hacking (Australia) were assessed for bioaccumulation and contamination. The current study aimed to assess metal concentrations in prawn tissue (tail muscle, exoskeleton, hepatopancreas and gills), relate whole body prawn tissue metal concentrations to sediment metal concentrations and animal size, as well as assess prawn consumption as a risk to human health. Metal concentrations were highest in sediment and prawns from contaminated locations (Iron Cove, Hen and Chicken Bay and Lane Cove) in Sydney estuary compared with the reference estuary (Port Hacking). Concentrations in sediments varied considerably between sites and between metals (As, Cd, Cr, Cu, Ni, Pb and Zn), and although concentrations exceeded Interim Sediment Quality Guideline-Low values, metals (As, Cd, Cr, Cu, Ni, Pb and Zn) were below Australian National Health and Medical Research Council human consumption guidelines in prawn tail muscle tissue. Metal concentrations in prawn tail muscle tissue were significantly different (p ≤ 0.05) amongst locations for Pb, Zn and Cd, and metal concentrations were generally highest in gills tissue, followed by the hepatopancreas, exoskeleton and tail muscle. The exoskeleton contained the highest Sr concentration; the hepatopancreas contained the highest As, Cu and Mo concentrations; and the gills contained the highest Al, Cr, Fe and Pb concentrations. Concentrations of Pb, As and Sr were significantly different (p ≤ 0.05) between size groups amongst locations.