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The effects of different astaxanthin levels on antioxidant capacity and non-specific immunity in phase V~X larvae of giant freshwater prawn, Macrobrachium rosenbergii , were investigated; furthermore, the differential gene expression was compared. For this experiment, 60,000 larvae were allocated into five treatments with six replicates. Astaxanthin supplementing in steamed eggs with graded effective content as 0 (control group, A 0 ), 50 (A 50 ), 100 (A 100 ), 200 (A 200 ), 400 (A 400 ) mg kg −1 were fed from phase V to X larvae respectively. Feeding trials lasted for 18 days. The results showed that acid phosphatase (ACP), alkaline phosphatase (AKP), total antioxidant capacity (T-AOC), glutathione reductase (GR), total superoxide dismutase (T-SOD) activities were declined significantly compared with the control ( P < 0.05); catalase (CAT) activities decreased among treatments; lysozyme (LZM) activities both in treatments A 50 and A 400 was lower than the control significantly ( P < 0.05), while the opposite phenomena were observed among other treatments; glutathione peroxidase (GSH-Px) activities both in treatments A 200 and A 400 significantly elevated than that among A 0 , A 50 , and A 100 ( P < 0.05). There was no significant difference in cytochrome oxidase activity (CCO) among treatments except that in A 100 ( P > 0.05). Nineteen common differential genes were screened out by means of transcriptome analysis. This study implies that excessive addition of astaxanthin may take a negative effect on larvae development of M. rosenbergii by way of suppressing the antioxidant system and non-specific immunity function, and its possible mechanisms need to be investigated furthermore.

Objective: The study aimed to assess the impact of dietary nucleotide (NT) supplementation on the growth performance and immune response of juvenile Macrobrachium rosenbergii. Materials and Methods: A commercial diet was supplemented with 0.0% (control), 0.10% (T1), 0.15% (T2), and 0.20% (T3) NT for the study. A total of 132 juvenile prawns (0.78 ± 0.03 gm) were randomly distributed into four groups, each having three replicates. Following the 75-day feeding trial, the experimental prawns were exposed to Aeromonas veronii at 8.35 × 105 colony forming unit (cfu)/ml for 7 days through a bath treatment. Results: The growth parameters and survival rate were significantly higher (p < 0.05) in NT-supplemented prawns. Immune-related parameters, e.g., total hemocyte count (THC), hemolymph protein, albumin, globulin, superoxide dismutase, and catalase activity, were also significantly higher (p < 0.05) in NT-supplemented prawns. The challenge of prawn with A. veronii resulted in a significant reduction (p < 0.05) in THC and other biochemical parameters of hemolymph and caused mortality in all the experimental groups. However, significantly higher survival (p < 0.05) against the A. veronii challenge was found in NT-supplemented prawns. Conclusion: It can be concluded that dietary NTs should be supplemented at 0.15%–0.2% to enhance the growth, immunity, and resistance of juvenile M. rosenbergii against A. veronii.

As an important freshwater economic shrimp, Macrobrachium rosenbergii (M. rosenbergii) possesses a certain tolerance to saline/alkaline conditions. Analyzing the damage mechanism and stress response of M. rosenbergii in saline/alkaline environments will provide a scientific basis for promoting ecological restoration through the utilization of saline/alkaline water resources for aquaculture. In the first experiment, the 96 h median lethal concentration (LC50) of NaHCO3 was determined for juvenile M. rosenbergii. A second experiment then exposed the shrimp to a control group and an alkaline water group set at 60% of the established LC50. After 96 h of exposure, gill tissue samples were collected from both groups for analysis. The aim was to clarify both the damage mechanisms induced by NaHCO3 and the response mechanisms. The current results indicated that acute NaHCO3 exposure reduced antioxidant enzyme activity and induced gill tissue damage in M. rosenbergii. In response to the stress caused by NaHCO3, M. rosenbergii activated immune-related enzymes as well as immune-related differentially expressed genes involved in endocytosis, autophagy, and the toll-like receptor signaling pathway. In summary, the current research provided reference information for understanding the adverse effects caused by saline/alkaline water stress and for the breeding of M. rosenbergii in saline/alkaline water environments.

Macrobrachium rosenbergii nodavirus (MrNV)—the aetiological agent of white tail disease—is a major limiting factor of crustacean aquaculture as it causes up to 100% mortality in M. rosenbergii larvae and juveniles. Despite the importance of MrNV, there have been few studies on the phylogenetic diversity and geographic range of this virus in Australian waterways. Here, we detected MrNV genomes in common carp (Cyprinus carpio) metatranscriptomes sampled at five freshwater sites across the Murray-Darling Basin (MDB), Australia. We identified genetic divergence of the RNA-dependent RNA polymerase gene between MrNV sequences identified in the northern and southern rivers of the MDB. Northern viruses exhibited strong phylogenetic clustering with MrNV from China, whereas the southern viruses were more closely related to MrNV from Australia. However, all five viruses were closely related in the capsid protein, indicative of genetic reassortment of the RNA1 and RNA2 segments between Australian and introduced MrNV. In addition, we identified Macrobrachium australiense in two of the five MrNV-positive libraries, suggesting that these species may be important reservoir hosts in the MDB. Overall, this study reports the first occurrence of MrNV outside of the Queensland region in Australia and provides evidence for genetic reassortment between endemic and introduced MrNV.

Mass mortalities of the larval stage of the giant freshwater prawn, Macrobrachium rosenbergii, have been occurring in Bangladesh since 2011. Mortalities can reach 100% and have resulted in an 80% decline in the number of hatcheries actively producing M. rosenbergii. To investigate a causative agent for the mortalities, a disease challenge was carried out using infected material from a hatchery experiencing mortalities. Moribund larvae from the challenge were prepared for metatranscriptomic sequencing. De novo virus assembly revealed a 29 kb single-stranded positive-sense RNA virus with similarities in key protein motif sequences to yellow head virus (YHV), an RNA virus that causes mass mortalities in marine shrimp aquaculture, and other viruses in the Nidovirales order. Primers were designed against the novel virus and used to screen cDNA from larvae sampled from hatcheries in the South of Bangladesh from two consecutive years. Larvae from all hatcheries screened from both years were positive by PCR for the novel virus, including larvae from a hatchery that at the point of sampling appeared healthy, but later experienced mortalities. These screens suggest that the virus is widespread in M. rosenbergii hatchery culture in southern Bangladesh, and that early detection of the virus can be achieved by PCR. The hypothesised protein motifs of Macrobrachium rosenbergii golda virus (MrGV) suggest that it is likely to be a new species within the Nidovirales order. Biosecurity measures should be taken in order to mitigate global spread through the movement of post-larvae within and between countries, which has previously been linked to other virus outbreaks in crustacean aquaculture.

Background Application of a virus-like particle (VLP) as a nanocontainer to encapsulate double stranded (ds)RNA to control viral infection in shrimp aquaculture has been extensively reported. In this study, we aimed at improving VLP’s encapsulation efficiency which should lead to a superior fighting weapon with disastrous viruses. Results We constructed 2 variants of chimeric Macrobrachium rosenbergii nodavirus (MrNV)-like particles (V1- and V2-MrN-VLPs) and tested their efficiency to encapsulate VP37 double stranded RNA as well as WSSV protection in P. vannamei. Two types of short peptides, RNA-binding domain (RBD) and deca-arginine (10R) were successfully engineered into the interior surface of VLP, the site where the contact with VP37-dsRNA occurs. TEM and dynamic light scattering (DLS) analyses revealed that the chimeric VLPs remained their assembling property to be an icosahedral symmetric particle with a diameter of about 30 nm, similar to the original MrN-VLP particle. The superior encapsulation efficiency of VP37-dsRNA into V2-MrN-VLP was achieved, which was slightly better than that of V1-MrN-VLP but far better (1.4-fold) than its parental V0-MrN-VLP which the mole ratio of 7.5–10.5 for all VLP variants. The protection effect against challenging WSSV (as gauged from the level of VP37 gene and the remaining viral copy number in shrimp) was significantly improved in both V1- and V2-MrN-VLP compared with an original V0-MrN-VLP template. Conclusion MrN-VLP (V0-) were re-engineered interiorly with RBD (V1-) and 10R (V2-) peptides which had an improved VP37-dsRNA encapsulation capability. The protection effect against WSSV infection through shrimp administration with dsRNA + V1-/V2-MrN VLPs was experimentally evident.

An assessment of heavy metal concentration in wild-captured Macrobrachium rosenbergii (giant freshwater prawns) from their natural habitat is important since it is susceptible to environmental pollution due to the rapid development and human activities along the Sarawak River. This study aimed to estimate the heavy metal contamination in muscles, exoskeletons and gills of the M. rosenbergii and to estimate the health risk assessment to human consumption. The concentration of heavy metals was analyzed by the flame atomic absorption spectrophotometer and the flow injection mercury system. The metal concentrations in prawns were detected in the following order: Hg < Cd < Co < Cu < Zn; in all body parts (P < 0.05), where a high concentration of metals was recorded in gills due to its function as the excretion site of contaminants from the body. A positive correlation of Co, Cu, and Zn in muscles and gills was observed with the increasing size of prawns. The human health risk assessment indicated a less potential adverse health effect of prawns for consumption from Sarawak River (hazard index values < 1). All samples contained metals below the Joint FAO/WHO Expert Committee on Food Additives (JECFA) permissible limit for human consumption (Cd < 2 mg/kg; Cu < 30 mg/kg; Zn < 150 mg/kg; Hg < 1 mg/kg). Therefore, M. rosenbergii from the Sarawak River were not contaminated enough to prevail high risk on human health, but regular monitoring is suggested for seasonal variability of heavy metals in M. rosenbergii for safeguarding human health.

Integrated rice–aquatic animal farming has become a vital strategy for enhancing food security. To assess the effects of integrated rice–giant river prawn (Macrobrachium rosenbergii) farming (IRPF) on agricultural ecosystems, we used 16S rRNA gene sequencing to analyze soil bacterial communities in comparison with traditional rice monoculture (RM). Our study revealed that the IRPF did not significantly affect the diversity of the soil bacterial community. However, during the initial culture stage, IRPF markedly increased the relative abundance of the phylum candidate division NC10 and the genus Candidatus Methylomirabilis, enhancing nitrogen-cycling-related functions within the bacterial community. Additionally, IRPF reduced the complexity and stability of these communities in the early to middle culture stages. While stochastic processes usually dominate the assembly of these communities, IRPF restricted bacterial migration and reduced the influence of these stochastic processes. Furthermore, IRPF had a significant impact on environmental factors within paddy soils, strongly correlating with shifts in bacterial communities, particularly through variations in soil nitrite concentration. In conclusion, the influence of IRPF on the bacterial community in paddy soils was primarily observed during the early and middle culture stages, and the impacts of IRPF on the soil bacterial community were primarily driven by environmental changes, especially soil nitrite concentration. These findings provide theoretical insights and a reference for understanding the microbiological impacts of different integrated rice–fish farming systems on agricultural ecosystems.

A 90-day experiment consisting of two groups, a biofloc treatment and a control treatment, was performed in six indoor cement ponds to investigate the effectiveness of biofloc technology (BFT) for maintaining water quality and growth performance of Macrobrachium rosenbergii in a zero-exchange water system. Molasses was added to the biofloc ponds with the C/N ratio of 20:1 based on the amount of daily feed. The floc volume in the biofloc group increased gradually (28.72 mL L −1 ) along with molasses addition, but the value in the relative control group remained at low levels (0.40–4.97 mL L −1 ) ( P  < 0.05). A total of 4.97% Bacillus , 4.20% Lactococcus , and 9.65% Nitrospira were determined in the biofloc water, and these values were significantly higher than that in the control water ( P  < 0.05). Ammonia-N, nitrite-N, nitrate-N, and total nitrogen concentrations in the biofloc water were significantly lower than that in the relative control group ( P  < 0.05). Potassium orthophosphate (PO 4 − -P) and total phosphorous (TP) concentrations increased consistently in both groups. The same-day value of PO 4 − -P concentration in the control group (6.37–12.96 mg L −1 ) was 1.5 higher than that of the biofloc group (4.66–7.99 mg L −1 ) from day 60 to day 90 ( P  < 0.05). Significant differences in TP concentration ( P  < 0.05) were noted between the control and biofloc groups from the 15th day to the 30th day and from the 60th day to the 90th day. The biofloc treatment resulted in a 10.62% higher survival rate, a 27.55% higher weight gain rate, and a 7.13% higher specific growth rate ( P  < 0.05). The findings of the present study demonstrated that BFT effectively promoted water quality, as well as growth and survival of M. rosenbergii , by regulating the inorganic nitrogen and phosphorus dynamics.

Current seasonal influenza A virus (IAV) vaccines are strain-specific and require annual reconstitution to accommodate the viral mutations. Mismatches between the vaccines and circulating strains often lead to high morbidity. Hence, development of a universal influenza A vaccine targeting all IAV strains is urgently needed. In the present study, the protective efficacy and immune responses induced by the extracellular domain of Matrix 2 protein (M2e) displayed on the virus-like particles of Macrobrachium rosenbergii nodavirus (NvC-M2ex3) were investigated in BALB/c mice. NvC-M2ex3 was demonstrated to be highly immunogenic even in the absence of adjuvants. Higher anti-M2e antibody titers corresponded well with increased survival, reduced immunopathology, and morbidity of the infected BALB/c mice. The mice immunized with NvC-M2ex3 exhibited lower H1N1 and H3N2 virus replication in the respiratory tract and the vaccine activated the production of different antiviral cytokines when they were challenged with H1N1 and H3N2. Collectively, these results suggest that NvC-M2ex3 could be a potential universal influenza A vaccine.