Giant River Research Articles

Larviculture of the freshwater prawn Macrobrachium spp. Spence Bate, 1868 (Decapoda, Palaemonidae): a comprehensive review

Abstract The freshwater prawns of the genus Macrobrachium Spence Bate, 1868, hold major potential for sustainable aquaculture intensification and diversification. Beyond the dominant giant river prawn M. rosenbergii (De Man, 1879), successful larviculture and domestication of additional species could boost production. However, inconsistent hatchery results have hampered the wider application and commercialization of cultivation protocols. This comprehensive review aims to analyse past larviculture research efforts to advance Macrobrachium farming practices. Several published studies documenting larviculture experiments on various Macrobrachium taxa are examined. Larval developmental patterns, optimal rearing salinity and temperature ranges, stocking densities, feeding regimes, and reported survival rates are compared within and among species. Significant inter- and intraspecific variability is apparent, highlighting the need for species-specific approaches. Past studies have applied generalized techniques derived from M. rosenbergii with varying success, further motivating the analytical review of findings. Key bottlenecks impeding consistent hatchery seed production are identified. In particular, knowledge gaps regarding larval nutritional needs, biofouling prevention, and weaning method optimization present ongoing challenges. By reconciling contradictory results and emphasizing biological nuances, this review distinguishes priorities for strengthening protocol development. Priorities include standardizing assessments, disseminating optimized techniques tailored to particular target species, and outlining future research directions. With reliable hatchery production, additional Macrobrachium species could be incorporated into polyculture or mono-crop systems, supporting livelihood diversification and sustainable intensification of aquaculture.

The importance of color and body size for reproductive decision making by males and females of the giant river prawn, Macrobrachium rosenbergii (de Man, 1879) (Decapoda, Caridea, Palaemonidae).

The selection and expression of conspicuous colorations in animals is often related to anti-predation strategies and sociosexual communication. The giant river prawn, Macrobrachium rosenbergii (de Man, 1879) is a species with three male morphotypes that vary in claws' coloration and the size of the animals. It has been suggested that male reproductive quality might be associated to their coloration, but evidence is still conflicting. In addition, a possible communication function of orange patches, that occupies a large portion of egg-bearing females' cephalothorax, has never been investigated before. For that matter, in this study, we evaluated the importance of visual cues for reproductive decision making by males and females of the giant river prawn. Through two-choice discrimination experiments, we verified whether: 1) females would be equally attracted to the presence of males expressing different claw colorations and body sizes; 2) female reproductive status and body size would influence males' decision making. Under the tested experimental conditions, females predominantly chose larger over smaller males, while males showed no significant preference for any kind of female. It is possible that body size is one of the cues that females use to identify males' morphotype. The choice of larger males could provide greater protection for females against harassment by other males. Further studies should employ visual cues in combination with chemical ones for a better understanding of mate choice in this species.

Transcriptome Profile and Gene Expression During Different Ovarian Maturation Stages of Macrobrachium rosenbergii (De Man, 1879).

Macrobrachium rosenbergii, or giant river prawn, is the most economically crucial cultured freshwater crustacean. A predominant challenge in developing crustacean aquaculture is reproduction management, particularly ovary maturation, where identifying regulative mechanisms at the molecular level is critical. Ovary is the primary tissue for studying gene and protein expressions involved in crustacean growth and reproduction. Despite significant interest in M. rosenbergii, its gene discovery has been at a relatively small scale compared to other genera. In this study, comprehensive transcriptomic sequencing data for different maturation stages of the ovary of M. rosenbergii were observed. The 20 female M. rosenbergii samples evaluated were categorised into four maturation stages, 1 to 4. A total of 817,793,14, 841,670,70, 914,248,78 and 878,085,88 raw reads were obtained from stages 1, 2, 3 and 4, respectively. The assembled unique sequences (unigenes) post-clustering (n = 98013) was 131,093,546 bp with an average size of 1,338 bp. The BLASTX unigene search against National Centre for Biotechnology Information (NCBI), non-redundant (NR), nucleotide sequence (NT), Kyoto Encyclopaedia of Genes and Genomes Orthology (KO), Swiss-Prot, Protein Family (PFAM), Gene Ontology (GO), and euKaryotic Orthologous Groups (KOG) databases yielded 27,680 (28.24%), 7,449 (7.59%), 13,026 (13.29%), 22,606 (23.06%), 29,907 (30.51%), 30,025 (30.63%) and 14,368 (14.65%) significant matches, respectively, totalling to 37,338 annotated unigenes (38.09%). The differentially expressed genes (DEG) analysis conducted in this study led to identifying cyclin B, insulin receptor (IR), oestrogen sulfotransferase (ESULT) and vitellogenin (Vg), which are critical in ovarian maturation. Nevertheless, some M. rosenbergii ovarian maturation-related genes, such as small ubiquitin-like modifier (SUMO)-activating enzyme subunit 1, E3 ubiquitin-protein ligase RNF25, and neuroparsin, were first identified in this study. The data obtained in the present study could considerably contribute to understanding the gene expression and genome structure in M. rosenbergii ovaries throughout its developmental stage.

Positive effects of a mixture of fish oil and soybean oil as a dietary lipid source on the ovarian development and health of female giant river prawn, Macrobrachium rosenbergii broodstock

Lipids are key nutrients that affect the development of the ovary in aquatic animals. This study aimed to investigate the effects of different lipid sources on the ovarian development and health of Macrobrachium rosenbergii broodstock. The M. rosenbergii broodstock, with an initial body weight of 8.07±0.74 g, were fed diets containing 5 % fish oil (FO), soya bean oil (SO), rapeseed oil (RO), coconut oil (CO), and a 1:1 mixture of fish oil and soybean oil (MO) as lipid sources for a period of 56 days. The results indicated that there were no significant differences in survival rate (SR) and hepatopancreatic index (HSI) among the different groups (P > 0.05). However, the specific growth rate (SGR) and gonadosomatic index (GSI) in the MO group were significantly higher than other groups (P < 0.05). Additionally, fatty acid levels in diets directly influenced the fatty acid composition of prawn hepatopancreas, showing a similar trend to that observed in the diet itself. Furthermore, compared to the other trial groups, haemolymph levels of 17-β estradiol (E2) and progesterone (PROG) were significantly increased in the MO group (P < 0.05). The ovarian section also exhibited better histomorphology and larger oocyte diameter in this group. Moreover, total antioxidant capacity was significantly increased in the MO group (P < 0.05). Saturated fatty acids in RO and CO groups could promote the expression of lipid synthesis-related genes fatty acid synthase (fas) and acetyl-CoA carboxylase (acc), concurrently suppressing the expression of lipid catabolism-related genes acyl-CoA oxidase-1 (acox-1) and AMP-activated protein kinase alpha (ampkα) (P < 0.05). Conversely, polyunsaturated fatty acids in the MO group significantly up-regulated the expression levels of fatty acid binding protein-3 (fabp-3) and peroxisome proliferator-activated receptor gamma (pparγ) (P < 0.05). Based on the findings of hepatopancreatic tissue structure, it was determined that the use of a single vegetable oil resulted in some damage to the hepatopancreatic tissue structure of M. rosenbergii broodstock, leading to increased oxidative stress. In conclusion, it is recommended that a 1:1 mixture of fish oil and soybean oil be used as a dietary lipid source to effectively meet the nutritional requirements during the ovarian development period of M. rosenbergii broodstock. This combination also enhances antioxidant properties, promotes the synthesis of haemolymph steroid hormones and lipid metabolism in female prawns, thereby facilitating ovarian development and overall health of M. rosenbergii broodstock.

Prioritising Conservation Area in Species Management Strategy for The Edible Bornean Giant River Frog Limnonectes leporinus Anderson 1923.

Limnonectes leporinus, the endemic giant river frog, is a riparian (stream dwelling) species that lives along streams with moderate to steep gradients. The most serious threats to the species are deforestation caused by severe clear cutting, which fragments its distribution, and overhunting for local consumption. Excessive landscape modification alters habitat, making it critical for an organism to maintain heterozygozity for the population to be fit to adapt to a changing environment. The goal of this research was to project suitable habitats and predict the potential for habitat connectivity to allow gene flow across the Sarawak landscape. The presence data file and environmental layers were converted into ASCII format using ArcGIS and then used in MaxEnt modelling to generate the map of suitable habitats. To perform the connectivity model, the potential habitat model and genetic attributes of haplotype data were computerised in Circuitscape software. The findings revealed that suitable habitats corresponded to species distribution in lowland areas with sustainable stream networks as breeding sites, while higher elevations were identified as unsuitable habitats. Gene flow data, on the other hand, revealed that connectivity circuits are mostly found in unprotected forest, which includes development areas and private lands. As a result, prioritising conservation areas should include local governments and landowners in proper landscape management as well as species management strategies. This indirectly sustains and protects Borneo's forests, flora and fauna.

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.

Aquacultural source of nitrous oxide revealed by nitrogen isotopes

The rapid expansion of coastal aquaculture has led to an increase in the coverage of aquaculture ponds, where intense feed-derived nitrogen is causing significant emissions of nitrous oxide (N2O). Multiple N2O production pathways and the relative importance of water column vs. sedimentary production in aquaculture ponds remain uncertain. Clarifying these pathways is vital for sustainable aquaculture development. Using 15N-labeled dissolved inorganic nitrogen, the pathways and rates of N2O production in subtropical aquaculture ponds located in south China, cultivating whiteleg shrimp, Japanese seabass, and giant river prawn, were successfully characterized. Total N2O production rates ranged from 6 to 70 µmol-N m−2 d−1, with the shrimp pond exhibiting the highest total N2O production rates, followed by ponds for seabass and prawn. These differences are primarily due to varying feed amounts causing differences in dissolved nutrients in water column and sediment. Particularly, nutrient and organic matter accumulation at the surface sediment stimulated N2O production. The oxygenated sediment on a centimeter scale could produce substantially more N2O compared to the water column above on a meter scale. Partial denitrification, i.e., nitrate and nitrite reduction to N2O, was more important (> 60 %) for N2O production in aquaculture ponds. The availability of nitrite is likely a major factor driving partial denitrification for both sedimentary and water column N2O production.

Total arsenic and arsenic species in selected seafoods: Analysis using high-performance liquid chromatography- inductively coupled plasma mass spectrometry and health risk assessment

The objective of the present study was to determine the inorganic and organic arsenic species and assess the actual risk of selected seafood produced in Sri Lanka in terms of inorganic arsenic species. A total of 80 samples, comprising 75 seafood samples and 5 freshwater samples, including mollusks, echinoderms, and crustaceans, were analyzed for their total arsenic (TA) levels and arsenic species. TA levels in seafood were determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after microwave digestion. Arsenic species, including arsenobetaine (AsB), arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA), were selectively separated and quantified using High-Performance Liquid Chromatography (HPLC) coupled to ICP-MS, following water bath extraction with 30 mmol/L nitric acid. The TA levels in seafood ranged from 0.036 to 11.686 mg kg-1. The spike recovery values for the five arsenic species lay within 80 % to 120 %, and the chromatographic recovery percentages ranged from 85.5 % to 123.6 %. In most samples, 100 % AsB was detected. Sea cucumber and both marine and freshwater giant river prawns showed AsB percentages of the total arsenicals at 83.2 %, 39.7 %, and 21.3 %, respectively. DMA was found in sea cucumber and marine giant river prawn at levels of 0.065 mg kg-1 and 0.048 mg kg-1, respectively, while MMA was not detected in any samples. AsIII was found in marine water giant river prawn and freshwater giant river prawn at levels of 0.010 mg kg-1 and 0.044 mg kg-1, respectively. AsV was only found in marine giant river prawn at a concentration of 0.193 mg kg-1. No other samples contained detectable levels of inorganic arsenicals. The Target Hazard Quotient (THQ) values for marine and freshwater giant river prawn were 0.90 and 0.2, respectively, indicating no significant health risks since the THQ values were <1. Therefore, our study suggests that consuming the studied seafood does not pose any health risks in terms of arsenic.

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.

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.

Current status of the global production chain of giant river prawn (Macrobrachium rosenbergii)

Objective: To determine the current state of the global production chain of Macrobrachium rosenbergii, identifying its links and the characteristics of the techniques used. Design/Methodology/Approach: Studies over a period of 20 years (2001-2022) about the production chain of M. rosenbergii were reviewed and analyzed. The information was synthesized in tables and the most relevant production and farming data are offered as an output. Results: The following links of the production chain were identified: production, processing, and commercialization. The Macrobrachium rosenbergii farming and the main technologies used to improve its production are described. Study Limitations/Implications: There is limited systemic information about the M. rosenbergii production chain. The topics addressed the specifics of production, processing, and marketing. Findings/Conclusions: To improve the M. rosenbergii production chain, the following aspects must be guaranteed: the supply of post-larvae (PL) specimens, the development of better monoculture practices, and its integration with other species of commercial importance. The organization of the production chain must also be reviewed, considering its direct and indirect participants.

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.

Characterization of a novel immune deficiency gene of Macrobrachium rosenbergii reveals antibacterial and antiviral defenses.

We sought to identify and characterize an immune deficiency (IMD) homolog from the giant freshwater prawn (also known as the giant river prawn) Macrobrachium rosenbergii. The IMD is a death-domain-containing protein that plays a crucial role as an adaptor protein in the IMD pathway-one of the most important response mechanisms to viral and bacterial invasion of invertebrates. An IMD homolog gene from M. rosenbergii (MrIMD) was isolated using rapid amplification of complementary DNA ends. The tissue distribution and response to immune challenge of MrIMD were analyzed by real-time reverse transcription polymerase chain reaction to understand the regulatory mechanism of MrIMD messenger RNA (mRNA) expression in M. rosenbergii. The open reading frame of MrIMD comprised 555 nucleotides encoding a protein consisting of 184 amino acids, with a conserved death domain at the C-terminus. The MrIMD protein demonstrated 53-74% similarity with IMDs from other crustaceans; the highest similarity was with the IMD from the oriental river prawn M. nipponense. Gene expression analysis revealed that MrIMD mRNA levels were highest in gill tissues. After Aeromonas hydrophila stimulation, MrIMD was significantly upregulated in the muscle, gills, and intestine, whereas there was no significant difference in the hemocytes and hepatopancreas. In the case of Macrobrachium rosenbergii nodavirus stimulation, MrIMD was dramatically upregulated in the muscle and hepatopancreas, whereas downregulation was observed in the gills. These results suggest that the MrIMD gene may play different roles in response to gram-negative bacteria and viral infection and plays a crucial role in innate immunity as an important key molecule in the defense against bacterial and viral infections.

Microbiota differences of giant river prawn (Macrobrachium rosenbergii) cultured in a recirculating aquaculture system (RAS) – A prototype vertical farming and traditional pond cultured system and their impact on autolysis rate and textural characteristics

Microbial profiles, autolysis rates, and textural characteristics of giant river prawn (Macrobrachium rosenbergii) cultured in a vertical farming with a recirculating aquaculture system (RAS) were compared to those of prawns cultured in a traditional pond system (Pond). Bioinformatics analysis revealed significant differences in the quantity and diversity of microbial communities between RAS and Pond. Firmicutes were the dominant phylum found in both samples but at higher levels in Pond (P < 0.05). Conversely, Tenericutes, Proteobacteria, and Actinobacteria, known as healthy microbiomes, were more abundant in RAS (P < 0.05). At the genus level, Enterococcus, recognized for its potential to improve colonization resistance against pathogens in the gut, was detected at higher levels in RAS (P < 0.005). This variation in microbiota might affect the difference in autolysis rates and textural properties between these two samples. RAS had a lower autolysis rate at all temperatures (4, 15, 25, and 35 °C) (P ˂ 0.05), consistent with the lower TCA-soluble peptide (157.61 μmol tyrosine equivalent/g sample). The differences in textural characteristics of these two prawns were observed. RAS had more water holding capacity (WHC) (80.07%) but lower drip loss (15.75%) and cooking loss (28.36%) than Pond (73.77, 17.84, and 31.20%, respectively) (P ˂ 0.05). From TPA results, RAS showed higher chewiness and gumminess than Pond, indicating a firmer texture, which is a desirable characteristic, particularly in fresh prawn. Overall, the findings indicated an improvement in microbial profiles, which further translated into economic benefits in terms of yield production and muscle quality, particularly texture, of prawn cultured in a recirculating aquaculture system as an alternative approach.

Comparative accumulation and effects of microplastics and microplastic-associated PCB-153 in the white hard clam (Meretrix lyrata) and giant river prawn (Macrobrachium rosenbergii) following chronic exposure

Global environmental abundance of microplastics (MPs) is increasing. MPs may sorb hydrophobic organic contaminants (HOCs), accumulate in and cause deleterious effects on exposed organisms. This study investigated and compared the accumulation and effects of MPs and MP-associated PCB in the two indigenous aquatic organisms in Viet Nam, the white hard clams, Meretrix lyrata, and the giant river prawns, Macrobrachium rosenbergii. The test organisms were exposed to either polyethylene microbeads (PEMBs), waterborne polychlorinated biphenyl 153 (PCB-153), or PEMB-associated PCB-153 (PEMB-PCB) over 28 days. Organismal MP accumulation, survival, and weight gain were examined at various sampling intervals. In general, MP accumulation was significantly greater in the clams than in the prawns. A significant quantity of MPs was observed in the digestive systems of the organisms after 0.5-day and during 28-day exposure. Although the effect of MPs and MP-associated PCB-153 on mean survival rate was not statistically significant, this effect was significant towards the end of the 28-day exposure. In addition, while MP-associated PCB-153 did not significantly affect the weight gain of the prawns, it significantly reduced weight gain in clams. Given the global increases of MPs and HOCs (and in southeast Asia specifically), and the importance of the hard clams and giant river prawns in the Indo-Pacific region, this present study provides valuable data to enhance our understanding of the effects of MPs and HOCs on these species.

Depletion kinetics of semicarbazide in giant river prawn (Macrobrachium rosenbergii) following nitrofurazone oral administration and its occurrence in an aquaculture farm

Semicarbazide (SEM), a marker residue used to monitor the use of prohibited drug nitrofurazone (NFZ), is commonly found in wild crustaceans, implying the natural origin. However, the difference between endogenous and exogenous SEM has rarely been investigated. So, tissue-bound SEM was determined in samples collected from giant river prawns cultured in an aquaculture farm and in samples from an experiment where giant river prawns were fed twice a day with NFZ at 30 mg/kg for 5 days. At day 10 of drug withdrawal, muscle SEM of the NFZ-fed prawn was 17.78 ng/g and depleted to 1.18 ng/g at day 90 (half-life 20.31 days) which was significantly higher than the control prawn (usually ≤ 0.1 ng/g). In contrast, the average SEM in the shell was independent of NFZ treatment. SEM was not found in the aquaculture farm samples, implying that the SEM in cultured prawn did not originate from SEM contamination.

Optical Coherence Tomography (OCT) Alterations Choice for Aquatic Organism Anatomy and Morphology Analysis: A Case Study of A Giant River Prawn (Macrobrachium Rosenbergii)

In this study, a Frequency Domain Optical Coherence Tomography (FD-OCT) system was utilized for non-invasive imaging of the giant river prawn (Macrobrachium rosenbergii) to analyze its anatomy and physiology. Seven tissue parts were examined: both stalked eyes (compound eyes), both sides of the carapace, the middle and lower ventral abdominal segments, and the uropod. The results indicated that FD-OCT was effective in detecting all the tissues studied. The deepest area detected was the eyestalks, with a range of approximately 930-1000 μm, while the shallowest detected areas were the ventral and dorsal segments, ranging from approximately 0-100 μm to 300-500 μm. This variance in detection range may be attributed to the dense exoskeleton and muscle bundles, which result in lower penetration in the ventral and dorsal segments compared to the eyestalks. Overall, this study demonstrated that FD-OCT can provide valuable insights into the tissue structure of giant river prawns and other crustaceans, offering significant benefits for further anatomical and physiological research.

The Dietary Lipid Requirement for Ovarian Maturation and Health in Female Giant River Prawn, Macrobrachium rosenbergii Broodstock.

The dietary lipid level is closely associated with ovarian maturation of broodstock. However, optimal lipid requirements during broodstock gonad development for aquatic animals remain limited. In order to assess the impact of dietary lipid levels (6%, 8%, 10%, 12%, and 14% lipid, denoted as L6%, L8%, L10%, L12%, and L14%) on the ovarian maturation, antioxidant status, and messenger RNA (mRNA) expression of genes involved in the lipid metabolism of Macrobrachium rosenbergii broodstock (initial weight 10.53 ± 1.97 g), this study carried out an 8-week feeding experiment. The findings showed that while there was no significant difference in the survival rate across the groups (p > 0.05), the weight gain observed in prawns fed the 8% lipid-level diet was significantly higher than those fed other diets (p < 0.05). The hepatosomatic index and the gonadosomatic index showed a significant increase with the rise in dietary lipid level (p < 0.05). More ovaries from M. rosenbergii broodstock reached stages Ⅲ and Ⅳ after being supplemented with dietary lipid levels between 8% and 14%. Serum glucose content did not show any significant difference among all groups (p > 0.05), but serum triglyceride and total cholesterol content increased followed by a decreasing trend with increasing levels of dietary lipids, both peaking in the prawns fed a 10% lipid-level diet. Furthermore, the progesterone (PROG) and 17β-estradiol (E2) content of prawns fed the 10% and 12% lipid-level diets were significantly higher compared to other groups (p < 0.05). Based on serum E2 and PROG content, the optimal lipid level needed for maximal ovarian maturation was determined to be 11.79% and 10.88%, respectively. Moreover, there were more endogenous vitellogenic oocytes in prawns fed 8% and 10% lipid-level diets, with a more compact arrangement compared to the less tightly arranged structure of the ovarian tissue in prawns fed other diets. With the increase in dietary lipid levels, there was a significant increase in the activity of superoxide dismutase. The activities of total antioxidant capacity and glutathione peroxidase initially increased and then decreased significantly, peaking at prawns fed 8% and 10% lipid-level diets, respectively (p < 0.05). The malondialdehyde content reached its lowest point in prawns fed a diet containing 10% lipid. In addition, the mRNA expressions of hepatopancreatic diacylglycerol acyltransferase and acetyl-CoA carboxylase showed the highest values in prawns fed a 10% lipid diet. Conversely, there was a significant decrease in the mRNA expression of carnitine palmitoyltransferase-1a in the hepatopancreatic as dietary lipid levels increased. The highest mRNA expression of fatty acid-binding proteins was observed in prawns fed an 8% lipid diet. In conclusion, dietary lipid levels ranging from 8% to 11.79% are beneficial for ovarian maturation and health of M. rosenbergii broodstock.