River Prawn Macrobrachium Research Articles

Genetic Diversity and Population Structure of Macrobrachium nipponense Populations in the Saline–Alkaline Regions of China

The oriental river prawn Macrobrachium nipponense is of great economic importance in China. However, its culture in the saline–alkaline regions is limited. This study used D-loop region sequences to analyze the genetic diversity and population structure across the saline–alkaline regions of China. A total of 264 individuals were successfully sequenced from nine sites, including Daqing in Heilongjiang Province (HLJ), Songyuan in Jilin Province (JL), Ulanhot in the east of inner Mongolia (NMG), Jingtai in Gansu Province (GS), Dongying in Shandong Province (SD), Dongtai in Jiangsu Province (JS), Nanchang in Jiangxi province (JX), Tianjin in mainland China (TJ), and Yinchuan in Ningxia Province (NX). In addition, 89 haplotypes were defined. The haplotype diversity (h) and nucleotide diversity π showed remarkable genetic diversity in the JS, NX, JL, and TJ sites. It was found that the genetic variation within sites was relatively greater. The genetic distance (D) and the pairwise genetic differentiation index (FST) revealed that SD and GS are closely related. The FST values among the nine sites were significant except for the one between SD and HLJ (p-value > 0.05). The cluster analyses and the phylogenetic tree identified two main groups. There is an association among sites by geographic location, and the JS site shows higher diversity. The results of this study provide basic information for the protection and development of M. nipponense resources in the saline–alkaline regions of China.

Impact of Soybean Bioactive Peptides on Growth, Lipid Metabolism, Antioxidant Ability, Molecular Responses, and Gut Microbiota of Oriental River Prawn (Macrobrachium nipponense) Fed with a Low-Fishmeal Diet

Impact of Soybean Bioactive Peptides on Growth, Lipid Metabolism, Antioxidant Ability, Molecular Responses, and Gut Microbiota of Oriental River Prawn (Macrobrachium nipponense) Fed with a Low-Fishmeal Diet

Effects of Chlamydomonas reinhardtii (Dangeard) Proteins Extracts on Storage Stability of Freshwater Shrimp Macrobrachium nipponense (De Haan)

In this study, the extraction of Chlamydomonas reinhardtii Dangeard (C. reinhardtii) protein was optimized through response surface methodology. The optimal extractions parameters were 0.091 mol/L sodium chloride concentration, 31.02 mL/g liquid to solid ratio, a homogenization frequency of 10.17 times per second, and a homogenization time of 12.82 minutes. The optimized protein extraction yield was 52.78%. The C. reinhardtii protein extract at different concentrations (0.1-0.5%) was used to dip-coat East Asian river prawn (Macrobrachium nipponense De Haan). Over a 4-day storage period, the pH value and total viable counts (TVC) of the prawn samples were determined every 24 hours. Results showed that a 0.2% C. reinhardtii protein extract effectively delayed increases in pH and TVC of the prawn samples, suggesting that C. reinhardtii protein extract could be a promising natural preservative.

Ferulic Acid Relieves the Oxidative Stress Induced by Oxidized Fish Oil in Oriental River Prawn (Macrobrachium nipponense) with an Emphasis on Lipid Metabolism and Gut Microbiota.

To investigate the potential of ferulic acid (FA) in attenuating the deleterious effects of oxidized fish oil (OF) on Macrobrachium nipponense, four experimental diets were formulated: 3% fresh fish oil (CT group, peroxide value: 2.2 mmol/kg), 3% oxidized fish oil (OF group, peroxide value: 318 mmol/kg), and 3% OF with an additional 160 and 320 mg/kg of FA (OF+FA160 group and OF+FA320 group, respectively). M. nipponense (initial weight: 0.140 ± 0.015 g) were randomly divided into four groups with six replicates (60 individuals per replicate) and reared for a period of 10 weeks. The results showed that the OF treatments significantly reduced the growth performance, the expression of antioxidant genes in the hepatopancreas, the levels of low-density lipoprotein cholesterol, and the gene expression levels of ACC, FAS, FABP10, ACBP, G6PDH, and SCD in the hepatopancreas (p < 0.05). OF supplementation significantly increased the levels of high-density lipoprotein cholesterol in hemolymph and the gene expression levels of CPT1 (p < 0.05). Addition of FA to the OF group significantly increased total bile acids (p < 0.05). In addition, it was found by Oil Red staining that the proportion of lipid droplets was significantly increased in the OF group (p < 0.05). However, the lipid droplets were alleviated by FA supplementation in the diet. OF was found to significantly reduce the diversity of intestinal microbiota by 16S rDNA sequencing and significantly increase the Firmicutes/Bacteroidetes (F/B) ratio (p < 0.05). Functional analysis of gut microbiota also showed that OF reduced lipolysis and led to fat deposition, which is related to gut microbiota. However, this study found that the composition of the gut microbiome of M. nipponense was changed by the addition of FA in the diet, including an increase in the abundance of Ruminococcaceae UCG-005 and Lachnospiraceae, a reduction in the F/B ratio, and an improvement in lipid metabolism. In conclusion, the OF induced oxidative stress, disturbed the balance of intestinal microbiota, promoted lipid accumulation, and caused disorders of lipid metabolism in M. nipponense by increasing lipid synthesis and reducing β-oxidation. However, the results of this study highlighted the potential of FA supplementation to modulate intestinal microbial composition, promote bile acid production, and activate genes related to lipid metabolism in the hepatopancreas, ultimately leading to a reduction in lipid deposition in M. nipponense.

A study on the functional role of the DHCR24 gene in gonadal differentiation and development of Macrobrachium nipponense

Sex differentiation in crustaceans is a complex process influenced by various factors, including the androgenic gland and sex-related genes. This study characterized the role of the Mn-DHCR24 gene in the oriental river prawn (Macrobrachium nipponense). We used bioinformatics to analyze sequence features and phylogenetic relationships of a single Mn-DHCR24 gene. The expression patterns of Mn-DHCR24 across different tissues and developmental stages were determined by real-time PCR, and its localization in testis was determined by in situ hybridization. RNA interference was used to knock down Mn-DHCR24 expression, followed by examining changes in sex ratio and gonadal development at the PL10 stage. Additionally, an enzyme-linked immunosorbent assay measured 17α-methyltestosterone levels, and tissue sections were used to characterize gonadal development. The results indicated that Mn-DHCR24 was high expression in testis, which was critical for sperm maturation and gonadal differentiation. RNAi experiments showed the role of Mn-DHCR24 during reproductive regulation rather than as a master gene for sex differentiation. This study further showed that Mn-DHCR24 regulated sex and hormone-related genes, influencing steroid biosynthesis pathways. Together, these findings provided valuable insights into the genetic and hormonal mechanisms of gonadal differentiation in M. nipponense, and supported the development of monosex culture technology.

Regulation Roles of Juvenile Hormone Epoxide Hydrolase Gene 2 in the Female River Prawn Macrobrachium nipponense Reproductive Process.

In this study, we investigated the regulatory roles of the juvenile hormone epoxide hydrolase (JHEH) gene in the reproductive process of female Macrobrachium nipponense. Its total cDNA length was 1848 bp, encoding for 460 amino acids. It contained conserved domains typical of epoxide hydrolases, such as the Abhydrolase family domain, the EHN epoxide hydrolase superfamily domain, and the "WWG" and "HGWP" motifs. The qPCR results showed that the expression of Mn-JHEH was the highest in hepatopancreas. Mn-JHEH was expressed at all stages of the embryonic and larval stages. The expression of Mn-JHEH at different developmental periods of the ovary was positively correlated with ovarian maturation. In situ hybridization showed that it was mainly located in the cytoplasmic membrane and nucleus of oocytes. The RNA interference technique was used to study the role of Mn-JHEH in the process of ovarian maturation. The knockdown of Mn-JHEH with dsRNA in the experimental group resulted in a significant decrease in the percentage of ovaries exceeding stage O-III and the gonadal index compared with the control group. On day 14 (the second molt), the molt frequency was significantly higher in the control group than in the experimental group. The results showed that Mn-JHEH played an important role in ovarian maturation and molting.

Polystyrene nanoplastics induce apoptosis, histopathological damage, and glutathione metabolism disorder in the intestine of juvenile East Asian river prawns (Macrobrachium nipponense)

Nanoplastics (NPs) are widely distributed in the aquatic environment and have become a global concern as a new type of pollutant. Many researchers have studied the physiological effects of NPs on aquatic organisms, but relatively little is known about their effects on intestinal immune function in crustaceans. Therefore, we used NPs concentrations of 0, 5, 10, 20, 40 mg/L for 28 days of stress, evaluated the effects of NPs exposure on intestinal cell apoptosis, histopathological damage, and glutathione (GSH) metabolism of juvenile East Asian river prawns (Macrobrachium nipponense). As NPs concentration increased, the contents of total GSH and oxidized glutathione decreased gradually (P < 0.05), the concentration of GSH first increased and then decreased (P < 0.05), and the activities of lysozyme, acid phosphatase, phenoloxidase, and alkaline phosphatase first increased and then decreased (P < 0.05). Additionally, intestinal tissue structure was damaged, and the apoptosis rate significantly increased (P < 0.05). The expression of intestinal autophagy genes (CTL, ALF, Crustin, ATG8, and BCL-2) increased at first and then decreased, the expression levels of TNF and Wnt4 significantly decreased, and the expression of Beclin significantly increased with increasing NPs concentration. We also found that AP-1 and PTEN were highly expressed in the hepatopancreas and were involved in intestinal immune responses. Our results showed that exposure to NPs may induce apoptosis of intestinal tissue cells, induce autophagy, and inhibit GSH metabolism, thereby reducing intestinal immune function of M. nipponense. These findings provide a reference for healthy aquaculture and ecological risk assessment of prawns.

Population dynamics and reproductive features of the Amazon River prawn Macrobrachium amazonicum (Heller, 1862) in Neotropical reservoirs under drought events

Here, we describe population and reproductive dynamics of four populations of Macrobrachium amazonicum in reservoirs during drought events. Additionally, we analyze possible phenotypic changes in this species promoted by fish predation. Two populations had a large-size phenotype (with large body proportions and morphotypes in males) while a small-size phenotype (with reduced sizes and no morphotypes) was found in the two other populations. Overall, females were larger than males and there were varying sex ratios among the four studied populations. All populations had bimodal or polymodal patterns in their monthly size-class frequency, suggesting a seasonal influence and a potentially great capacity of these populations to adapt to adverse environmental conditions. No major changes were found in the patterns of sex ratio, recruitment, frequency of (larger) male morphotypes and female ovarian development stages during drought events. Macrobrachium amazonicum is a resilient species and undergoes continuous reproduction. Females with immature ovaries were predominant in all populations, performing multiple spawns and exhibiting rapid ovarian development cycles. In males, the initial morphotype (TC - translucent claw) was predominant in populations with a social hierarchy. Males of dominant morphotypes (GC1 and GC2 - green claw 1 and 2) use more energy to carry out and maintain metabolic processes, which could probably one of the explanations why their number in populations are limited. We did not find any clear evidence that fish predation affected phenotypes, suggesting that phenotypic plasticity could be more related to intrinsic factors, which would have to be further investigated.

Prospects for the Spread of the Invasive Oriental River Prawn Macrobrachium nipponense: Potentials and Risks for Aquaculture in Europe

Climate change has amplified the threat posed by aquatic invasive species as potential disruptors of biodiversity and ecosystem functioning. Species Distribution Models (MaxEnt) based on original data and ecological variables have identified contemporary seven global centers of the oriental rivel prawn Macrobrachium nipponense distribution: the native range in East Asia, Northern, Western and Eastern Europe, the Irano-Turanian region, and North and South America. By 2050, further expansion in Europe is expected, likely due to climate change, particularly temperature changes (Bio1) and rain precipitation during the warmest quarter (Bio18). However, the species may see a range reduction in southern Europe due to lower precipitation and increased droughts related to climate change. Therefore, a northward shift in the range of the species is also predicted. In the context of global change, and especially biological invasions, this study highlights the risks of introducing aquaculture based on M. nipponense and recommends controlling such economic activities, which are associated with a high risk for native species and ecosystems. Further, long-term monitoring is needed to assess impacts and to efficiently manage M. nipponense populations that are already present in their non-native habitats, for mitigating their negative effects on native species and ecosystems worldwide.

Safe concentration, unsafe effects: Impact of BPA on antioxidant function in the hepatopancreas and ovarian gene expression in oriental river prawns (Macrobrachium nipponense)

This study investigated the effects of Bisphenol A (BPA), a common endocrine-disrupting chemical, on the antioxidant enzyme activities in the hepatopancreas and the expression of genes related to ovarian development in oriental river prawns (Macrobrachium nipponense). The 24hLC50 and 48hLC50 values for BPA were 80.59 mg/L and 63.90 mg/L, respectively, with a safe concentration of 12.06 mg/L. Prawns were exposed to low (4.85 mg/L), safe (12.06 mg/L), and high (30.00 mg/L) concentrations of BPA for 10 days to measure enzyme activities, and for 20 days followed by 7 days in BPA-free water to measure gene expression.Short-term exposure (12 h, 1d, 3d) to low concentration BPA did not significantly affect superoxide dismutase (SOD) activity in the hepatopancreas (P > 0.05), but long-term exposure (6d, 10d) significantly reduced SOD activity (P < 0.05). Catalase (CAT) activity showed no significant changes throughout the low concentration exposure period (P > 0.05). At safe and high concentrations, SOD and CAT activities significantly decreased after 12 h of exposure (P < 0.05).BPA affected heat shock protein 90 (HSP90) expression in the ovary, with low concentration BPA significantly upregulating HSP90 after 1 day (P < 0.05), but returning to normal levels after 10 and 20 days. At the safe concentration, HSP90 was significantly upregulated at all three sampling points (1d, 10d, 20d) (P < 0.05), while high concentration exposure led to significant upregulation only on day 10 (P < 0.05).Low concentration BPA had no significant effect on Cathepsin B (CB) and Cathepsin L (CL) gene expression in the ovaries (P > 0.05). However, safe concentration exposure promoted CB expression on days 1, 10, and 20 (P < 0.05), while high concentration exposure significantly increased CB expression on day 1 (P < 0.05), with levels returning to normal on days 10 and 20. CL expression significantly increased after 20 days of exposure to both safe and high concentrations (P < 0.05). Gene expression levels in the ovaries returned to normal after transfer to BPA-free water, with HSP90 and CB normalizing by day 1, and CL by day 7.These results indicate that even safe concentrations of BPA impose stress on the hepatopancreas and increase the expression of HSP90, CB, and CL genes in the ovaries, affecting ovarian development. And, these effects are reversible within a certain period after the removal of BPA.

Sustainable aquaculture of West African freshwater prawns Macrobrachium vollenhovenii (Herklots, 1857) and M. macrobrachion (Herklots, 1851) (Decapoda: Caridea: Palaemonidae)

Abstract The river prawn Macrobrachium vollenhovenii (Herklots, 1857) and the brackish river prawn M. macrobrachion (Herklots, 1851) are economically and ecologically significant West African species. Recent molecular studies suggest they might be different ecotypes of the same species, complicating taxonomy and sustainable aquaculture practices. Both species face significant threats from human exploitation, leading to high exploitation rates and smaller average sizes within populations. Seasonal variations affect their abundance, with M. macrobrachion more prevalent during the rainy season and M. vollenhovenii thriving in the dry season. Their omnivorous detritivorous feeding habits involve consuming detritus, diatoms, phytoplankton, and insect larvae during juvenile stages. Aquaculture of M. vollenhovenii and M. macrobrachion encounters difficulties such as limited hatchery technology and low larval survival rates. Efforts to cultivate juveniles or adults in captivity face obstacles like high mortality rates due to moulting stress, handling, feeding, and cannibalism. Reintroducing captive-bred prawns into the wild offers dual benefits: controlling snail populations that host parasite causing schistosomiasis and restoring ecological balance while enhancing local fisheries and providing socio-economic benefits. To achieve sustainable aquaculture, it is crucial to address taxonomic complexities, implement management measures to mitigate overexploitation, improve hatchery technology, optimise feeding strategies, reduce stress during moulting and handling, and engage local communities through capacity building and awareness programs. This review aims to contribute to a better understanding of these prawns, promoting informed decision-making for sustainable management, conservation, and socio-economic benefits in West Africa.

Integration of Gut Microbiota with Transcriptomic and Metabolomic Profiling Reveals Growth Differences in Male Giant River Prawns (Macrobrachium rosenbergii).

The giant freshwater prawn (GFP; Macrobrachium rosenbergii), a tropical species cultured worldwide, has high market demand and economic value. Male GFP growth varies considerably; however, the mechanisms underlying these growth differences remain unclear. In this study, we collected gut and hemolymphatic samples of large (ML), medium (MM), and small (MS) male GFPs and used the 16S rRNA sequencing and liquid chromatography-mass spectrometry-based metabolomic methods to explore gut microbiota and metabolites associated with GFP growth. The dominant bacteria were Firmicutes and Proteobacteria; higher growth rates correlated with a higher Firmicutes/Bacteroides ratio. Serum metabolite levels significantly differed between the ML and MS groups. We also combined transcriptomics with integrative multiomic techniques to further elucidate systematic molecular mechanisms in the GFPs. The results revealed that Faecalibacterium and Roseburia may improve gut health in GFP through butyrate release, affecting physiological homeostasis and leading to metabolic variations related to GFP growth differences. Notably, our results provide novel, fundamental insights into the molecular networks connecting various genes, metabolites, microbes, and phenotypes in GFPs, facilitating the elucidation of differential growth mechanisms in GFPs.

Apparent Digestibility Coefficients of Nutrients and Energy from Animal-Origin Proteins for Macrobrachium rosenbergii Juveniles

In prawn farming, the main protein source used in aquafeed formulations is fishmeal. Nevertheless, one estimates that in the coming years, this protein source will no longer be able to meet the demand for the activity. The search for new ingredients is important to meet the increasing demand and minimize environmental impacts, such as the reduction in fish stocks and the eutrophication of aquatic systems. The objective of this study was to determine the apparent digestibility coefficients of dry matter (DM), crude protein (CP), gross energy (GE), and ether extract (EE) of fishmeal, poultry co-products (viscera and hydrolysed feather), and insect meal (Gromphadorhina portentosa) for giant river prawn (Macrobrachium rosenbergii) juveniles. To determine the apparent digestibility coefficients (ADCs), 90 prawns (average weight, 15 g) were randomly distributed among three experimental units. The reference feed was formulated according to the requirements of the giant river prawn, with 35% crude protein and a gross energy of 3600 kcal kg−1. The test diets comprised 70% of the reference diet and 30% of the respective test ingredients. Prawns were fed three times a day until apparent satiety. Faeces were collected using the indirect siphoning method, twice a day at the same feeding site (at 7:30 a.m. and 6:30 p.m.). The water parameters were temperature (27 °C), dissolved oxygen (6.65 mg L−1) and pH (7.76). The ACDs of DM, CP, EE, and GE were, respectively, 61.48; 88.28; 99.89 and 88.25 for fishmeal; 76.48; 81.55; 97.29 and 85.13 for poultry viscera meal; 73.82; 75.21; 73.17 and 76.42 for hydrolysed feather meal; and 52.35; 59,48; 87.95 and 67.64 for G. portentosa meal. The values of protein (%) and digestible energy (kcal kg−1) were 55.20 and 3711 for fishmeal; 47.27 and 4285 for poultry viscera’s meal; 65.03 and 4145 for hydrolysed feather meal; and 47.72 and 3616 for G. portentosa meal. These results showed the potential use of insect meals and poultry co-products as ingredients for the diets of M. rosenbergii juveniles, as they present digestible values close to those found for fishmeal, the main raw material used in aquaculture diets.

A Chromosome-level genome assembly of giant river prawn (Macrobrachium rosenbergii)

The giant river prawn (Macrobrachium rosenbergii) is one of the most widely cultured crustacean species. In recent years, its aquaculture has faced challenges, including the degradation of germplasm resources and the emergence of viral diseases. Genomic information can be a valuable resource for developing molecular breeding programs for this important aquaculture species. Here we constructed a high-quality reference genome for M. rosenbergii by integrating Nanopore, Illumina, and high-throughput chromosome conformation capture (Hi-C) technologies. The final genome assembly is 3.18 Gb in size, with scaffold N50 and contig N50 of 62.73 Mb and 8.92 Mb, respectively. Approximately 98.6% of the assembled sequences were anchored into 59 pseudo-chromosomes. Benchmarking Universal Single-Copy Orthologs (BUSCO) benchmark of the genome assembly reached 94.5%. Repetitive sequences comprise 43.77% of the assembled genome, and 17,436 protein-coding genes were annotated. The high-quality genome of M. rosenbergii will empower molecular breeding efforts and provide invaluable resources for comparative genomic analysis of decapod species.

Alterations in Soil Bacterial Community and Its Assembly Process within Paddy Field Induced by Integrated Rice–Giant River Prawn (Macrobrachium rosenbergii) Farming

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.

Comparative transcriptome analysis reveals the different responding mechanisms of ovary and hepatopancreas following polyI:C challenge in Macrobrachium nipponense

The ovary in mammals has developed specialized mechanisms for protection against pathogen infections; however, the understanding of the innate immune system in the ovary of crustaceans is still limited. To elucidate the ovary's defense mechanisms in response to viral challenges, we subjected oriental river prawns (Macrobrachium nipponense) to poly I:C, a double-stranded RNA analog that emulates viral dsRNA, and analyzed the ovary's transcriptome profiles. Concurrently, RNA-seq analysis was performed on the hepatopancreas, a well-recognized immune-related tissue, following poly I:C challenge to investigate the distinct response mechanisms of the ovary and hepatopancreas and to gain a comprehensive understanding of the immune responses in both tissues. The results indicate that 1368 genes are differentially expressed in the ovary, with 903 genes upregulated and 465 genes downregulated. Subsequent analysis reveals that these differentially expressed genes (DEGs) include numerous genes associated with innate immunity, such as members of the C-type lectin, fibrinogen-related protein (Frep), Toll-like receptor, and NOD-like receptor (NLR) gene families, as well as acid phosphatase, scavenger receptor, crustin, Down syndrome cell adhesion molecule (Dscam), hemocyanin, and lipopolysaccharide and beta-1,3-glucan binding protein (LGBP). Furthermore, the DEGs include several genes related to ovary development, such as sox8, vitellogenin, progranulin, cyclin-dependent kinase, ecdysone receptor, frizzled, and members of the Fox gene family. In the hepatopancreas, a total of 729 DEGs were identified. Comparison of the DEGs in both tissues indicates that only 91 genes are common to both groups, highlighting significant tissue-specific responses to poly I:C stimulation. This study aims to enhance our understanding of the immune protective mechanisms employed by the ovary in response to pathogen exposure and establishes a foundation for investigating ovarian reproductive immunity in crustaceans.

Mitigation of mechanical damage and protein deterioration in giant river prawn (Macrobrachium rosenbergii) by multi-frequency ultrasound-assisted immersion freezing

In order to investigate the effects of multi-frequency ultrasound-assisted immersion freezing (MUIF) on the meat quality of Macrobrachium rosenbergii, tail meat was subjected to different MUIF treatments respectively, namely 20 + 40 kHz (MUIF-20 + 40), 20 + 60 kHz (MUIF-20 + 60), 40 + 60 kHz (MUIF-40 + 60) and 20 + 40 + 60 kHz (MUIF-20 + 40 + 60), and the immersion freezing (IF) as control. Results showed that average diameter of ice crystals was 28 μm in IF, and that was only 8 μm in MUIF-20 + 40 + 60. When compared to IF, MUIF alleviated oxidative deterioration of lipids and proteins, but only at higher ultrasound frequency (MUIF-40 + 60; MUIF-20 + 40 + 60). Carbonyl content of MUIF-20 + 40 + 60 was only 40% of that in IF. Similarly, protein denaturation was inhibited in MUIF (except for MUIF-20 + 40). Transmission electron microscopy showed greater distortion of the ultrastructural components in IF, MUIF-40 + 60, and MUIF-20 + 40 + 60, suggested by bended Z-line. In conclusion, MUIF can be an effective strategy to mitigate mechanical damage and protein deterioration in the meat of Macrobrachium rosenbergii.

Dietary fishmeal substitution with Antarctic krill meal improves the growth performance, lipid metabolism, and health status of oriental river prawn (Macrobrachium nipponense)

Aims to assess the effects of dietary inclusion of Antarctic krill meal (KM), five experimental diets supplemented with graded levels of KM (0 %, FM; 5 %, KM5; 10 %, KM10; 15 %, KM15; 20 %, KM20; 0 %, 13.3 %, 26.7 %, 40.0 %, and 56.7 % replacement fishmeal levels, respectively), were prepared to feed oriental river prawn (Macrobrachium nipponense) (0.20 ± 0.01 g) for 8 weeks. The results revealed significant improvements in weight gain rate (WGR), specific growth rate (SGR), feed conversion rate (FCR), and protein efficiency ratio (PER) at the inclusion of 5 %-20 % KM (P < 0.05). In the KM10 and KM15 groups, the concentrations of hemolymph total protein (TP), albumin (ALB), triglycerides (TG), high-density lipoprotein (HDL), and hepatopancreatic glutathione (GSH) were observed to be significantly higher compared to the FM group (P < 0.05). Conversely, the contents of hepatopancreatic malondialdehyde (MDA), total nitric oxide synthase (TNOS), and inducible nitric oxide synthase (iNOS) were significantly lower in the KM10 and KM15 groups compared to the FM group (P < 0.05). The mRNA expression levels of dorsal protein (dorsal), heat shock protein 60 (hsp60), and myeloid differentiation factor 88 (myd88) in the hepatopancreas in the KM10 group exhibited the lowest level. Additionally, compared to the FM group, the expression levels of fatty acid synthase (fas) and acetyl CoA carboxylase (acc) were significantly upregulated (P < 0.05), while the acyl CoA bindingprotein (acbp), carnitine palmitoyltransferase I (cpt I), and scavenger receptor B I (sr-b I) were significantly downregulated in the KM10 group (P < 0.05). In addition, the results of histopathology sections showed that 5–15 % KM could improve the health status of hepatopancreas and was a safe alternative to fishmeal. Overall, the optimal KM inclusion level in feed was 12.96 % (substituting for 34.60 % fishmeal) based on the quadratic fitting curve calculations of WGR and SGR.

Molecular characterization and functional identification of the insulin-like peptides receptor gene in the oriental river prawn Macrobrachium nipponense

The insulin-like signaling pathway plays diverse biological roles in regulating metabolism, immune responses, growth, and development in invertebrates. The insulin-like peptides (ILP) receptor (ILPR) is the pivotal protein in any insulin-like signaling pathway. In our previous study, we cloned the Mn-ILP gene from the oriental river prawn Macrobrachium nipponense and elucidated its function. However, the ILPR has not yet been described in M. nipponense. In the present study, we further examined the function of Mn-ILPR in M. nipponense. The full length of the Mn-ILPR mRNA was 4790 bp, encoding 1412 amino acids. Mn-ILPR was a transmembrane receptor under a subfamily of receptor tyrosine kinases. The Mn-ILPR mRNA was predominantly expressed in muscle and hepatopancreas. To elucidate the function of Mn-ILPR, we investigated its expression in different growth stages of prawns of both sexes, in prawns of different sizes at the same time, and in prawns of the same size at different stages of the molt cycle using qRT-PCR. The expression of Mn-ILPR was markedly higher: (1) in the rapid growth stage than in other stages of male individuals; (2) in the normal growth stage than in the gonad development stage of female individuals; (3) in large male individuals than in small male individuals; and (4) in the intermolt stage than in other stages of the molt cycle. Furthermore, the long-term knockdown of Mn-ILPR by RNAi effectively delayed the growth speed of M. nipponense. Meanwhile, the short-term knockdown of Mn-ILPR revealed that the ILP-ILPR signal pathway played a part in the process of growth of M. nipponense. These findings provide a greater understanding of the molecular mechanisms underlying growth and development in crustaceans.

Metagenomic dissection of the intestinal microbiome in the giant river prawn Macrobrachium rosenbergii infected with Decapod iridescent virus 1

Microbiome in the intestines of aquatic invertebrates plays pivotal roles in maintaining intestinal homeostasis, especially when the host is exposed to pathogen invasion. Decapod iridescent virus 1 (DIV1) is a devastating virus seriously affecting the productivity and success of crustacean aquaculture. In this study, a metagenomic analysis was conducted to investigate the genomic sequences, community structure and functional characteristics of the intestinal microbiome in the giant river prawn Macrobrachiumrosenbergii infected with DIV1. The results showed that DIV1 infection could significantly reduce the diversity and richness of intestinal microbiome. Proteobacteria represented the largest taxon at the phylum level, and at the species level, the abundance of Gonapodya prolifera and Solemya velum gill symbiont increased significantly following DIV1 infection. In the infected prawns, four metabolic pathways related to purine metabolism, pyrimidine metabolism, glycerophospholipid metabolism, and pentose phosphate pathway, and five pathways related to nucleotide excision repair, homologous recombination, mismatch repair, base excision repair, and DNA replication were significantly enriched. Moreover, several immune response related pathways, such as shigellosis, bacterial invasion of epithelial cells, Salmonella infection, and Vibrio cholerae infection were repressed, indicating that secondary infection in M. rosenbergii may be inhibited via the suppression of these immune related pathways. DIV1 infection led to the induction of microbial carbohydrate enzymes such as the glycoside hydrolases (GHs), and reduced the abundance and number of antibiotic-resistant ontologies (AROs). A variety of AROs were identified from the microbiota, and mdtF and lrfA appeared as the dominant genes in the detected AROs. In addition, antibiotic efflux, antibiotic inactivation, and antibiotic target alteration were the main antibiotic resistance mechanisms. Collectively, the data would enable a deeper understanding of the molecular response of intestinal microbiota to DIV1, and offer more insights into its roles in prawn resistance to DIVI infection.