River Prawn Research Articles

Cloning, functional and regulation analysis of a novel male reproduction-related protein gene from the oriental river prawn Macrobrachium nipponense

Gonadogenesis processes in crustaceans are complex. There, however, has been a large amount of research focused on regulation of female gonad (ovary) development in crustaceans, however, there has been little focus on the male gonad (testis). In the current study, a novel male reproduction-related protein gene (Mn-MRP) was identified from Macrobrachium nipponense. The relative abundance of Mn-MRP mRNA transcript in tissues and at different developmental stages were investigated. The relative abundance of Mn-MRP mRNA transcript was larger in the testis than other tissues, and during the testis maturation stage than at other developmental stages, suggesting Mn-MRP may have important functions in reproduction processes. The RNA interference (RNAi) was used to further investigate the Mn-MRP biological function. Silencing of the Mn-MRP gene effectively decreased the abundance of the sperm gelatinase (Mn-SG) mRNA transcript, implying the protein encoded by this gene may have functions in sperm activity during the fertilization process. Further studies with RNAi and eyestalk ablation confirmed that gonad inhibiting hormone gene (Mn-GIH) is a negative regulator of Mn-MRP, and that the insulin-like androgenic gland hormone gene (Mn-IAG) is a positive regulator. There, therefore, was cloning of the Mn-MRP gene, and investigation of its potential biological function, as well as elucidation of the positive/negative regulators in current study. The results from this study provide for a greater understanding of regulatory mechanisms of male reproduction in crustaceans.

Dietary α-lipoic acid requirement and its effects on antioxidant status, carbohydrate metabolism, and intestinal microflora in oriental river prawn Macrobrachium nipponense (De Haan)

Alpha lipoic acid (α-LA) is not only a natural antioxidant, but also a key cofactor for the enzymes pyruvate dehydrogenase and α-ketoglutarate dehydrogenase. The purpose of this study was to investigate the effects of dietary α-lipoic acid on the growth, antioxidant status, carbohydrate metabolism, and intestinal microflora of prawn, Macrobrachium nipponense. A total of 1250 juvenile M. nipponense with an average body weight of 0.050 ± 0.003 g were randomly divided into five groups with three replicates (50 prawns per tank) for an 8-week feeding trial. The groups were fed with basal semi-purified diets containing α-lipoic acid at five different concentrations: 0 mg/kg (LA1), 500 mg/kg (LA2), 1000 mg/kg (LA3), 2000 mg/kg (LA4) and 4000 mg/kg (LA5). The results showed that the weight gain (WG), specific growth rate (SGR) and the survival rate were significantly lower in LA5 than in other groups. Dietary α-lipoic acid at a concentration below 2000 mg/kg (LA4) significantly reduced the malondialdehyde (MDA) content and increased the glutathione (GSH) content in the hepatopancreas of M. nipponense, and significantly increased the activities of glutathione reductase (GR), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD). However, the MDA content in the hepatopancreas was higher in LA5 than in LA1. The prawns in the LA3 group showed the highest activities of isocitrate dehydrogenase (ICDH) and key enzymes in glycolysis (pyruvate kinase, PK; 6-phosphofructokinase, PFK; Hexokinase, HK), but lower activity of lactate dehydrogenase (LDH) compared with those in LA1 and LA2. Analyses of gut microflora at the operational taxonomic unit (OTU) level indicated that abundance (Chao index) and diversity (Simpson index) were lower in LA5 than in LA1 and LA3. The Shannon index's index was highest in LA5. The intestinal flora of M. nipponense comprised five main phyla and five main bacteria. The proportions of Proteobacteria and Citrobacter were higher in LA3 and LA5 than in LA1. The proportions of Actinobacteria, Bacteroidetes Aeromonas, Tyzzerella_3 and Mycobacterium were significantly higher in LA5 than in LA3 and LA1. In summary, dietary α-lipoic acid at an appropriate level (<2000 mg/kg) can improve the antioxidant capacity and carbohydrate metabolism of M. nipponense and modulate its intestinal microbiota without reducing growth performance. Excessive α-lipoic acid (4000 mg/kg) negatively affected the growth performance and antioxidant activity of M. nipponense. Calculations based on WG and SGR indicate that the optimal addition amount of α-lipoic acid for juvenile M. nipponense is 1354.8 mg/kg and 1329.92 mg/kg, respectively.

Variations of digestive enzymatic activity of the longarm river prawn, Macrobrachium tenellum (Smith 1871) adapted from the wild to culture with prepared meals

AbstractMacrobrachium tenellum is an omnivorous freshwater prawn living in rivers near the coast and in coastal lagoons with potential to be cultured. It is distributed in rivers, estuaries, and coastal lagoons, and in each of those habitats, it has access to food items with different features and nutritional content. In this research, it has been tested if this variety of food availability has an immediate effect on their digestive enzymatic activity once animals are brought to laboratory and fed with different meals. Wild prawns were captured in a river and coastal lagoon, and after acclimation, they were fed with three different experimental diets. Total alkaline protease, trypsin, chymotrypsin, lipase, and α amylase were measured from prawns fed experimental diets at 15 and 30 days. There were significant differences in the enzymatic activity of prawns depending on their original habitat and diet. However, the proportion in which these enzymes are expressed in the prawns from different treatments remains proportional to what was observed in wild specimens, as reported in previous research. We consider that the study of this phenomenon can contribute to a better understanding of the nutritional needs of this species if a species‐specific diet needs to be prepared.

Improving the Efficiency of Lambari Production and Diet Assimilation Using Integrated Aquaculture with Benthic Species

A single farmed fish species assimilates about 20% of the nutrients in the supplied diet. This study evaluated if the culture of complementary ecological-function species can recover nutrients dispersed into water and transform them into high-valued biomass. A completely randomized experiment was designed with three treatments and four replications of each production system: monoculture of lambari (Astyanax lacustris); integrated aquaculture of lambari and Amazon river prawn (Macrobrachium amazonicum); and integrated aquaculture of lambari, Amazon river prawn, and curimbatá (Prochilodus lineatus). Fingerlings of lambari (0.8 ± 0.8 g) were stocked in twelve earthen-ponds (0.015 ha) at the density of 50 fish m−2. Eight ponds were stocked with juveniles of Amazon river prawn (1.1 ± 0.2 g) at the density of 25 prawn m−2. Four of these eight ponds were stocked with curimbatá fingerlings (0.2 ± 0.1 g) at a density of 13 fish m−2. Only lambari was fed twice a day with an extruded commercial diet. The experiment lasted 60 days when lambari attained commercial size. The inclusion of prawn increased the total species yield from 1.8 to 2.4 t ha−1 cycle−1 and reduced the feed conversion ratio (FCR) from 2.5 to 1.8. The inclusion of prawn and curimbatá increased the total yield to 3.2 t ha−1 cycle−1 and reduced the FCR to 1.4. Therefore, the integrated culture of lambari, prawn, and curimbatá improves the use of space, water, feed, and benthic species to recover the large quantity of nutrients accumulated in the bottom of lambari pond production, converting them into high-nutritional and monetary-valued biomass.

Effects of ammonia and nitrite on food consumption of the Amazon River prawn Macrobrachium amazonicum (Heller, 1862) postlarvae

Experiments were carried out to study the effects of ammonia and nitrite on food consumption of Macrobrachium amazonicum postlarvae. Postlarvae (average weight of 0.0625 g) were exposed during 21 days to four concentrations of total ammonia (0, 1.05, 2.1 and 4.2 mg. NH3+NH4+ L-1) and four concentrations of nitrite (0, 0.075, 0.15 and 0.30 mg N-NO2- L-1). After the exposure period, six prawns per treatment were maintained individually in 250 mL experimental units to analyze the food consumption as a function of the amount of food offered and the leftovers during a 24 h period. The food consumption presented significant alterations for prawns exposed to all nitrite concentrations and at concentrations of twice the recommended safety level for total ammonia. According to the results obtained, high concentrations of total ammonia and nitrite affect the food consumption of M. amazonicum adversely, influencing the species performance in culture systems.

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

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

Transcriptome analysis of hepatopancreas from different living states oriental river prawn (Macrobrachium nipponense) in response to hypoxia

As an important economical freshwater prawn, Macrobrachium nipponense has difficulty with adapting to hypoxia. In this study, comparative transcriptome analysis was used for the first time to explore the differences between different living states of Macrobrachium nipponense under hypoxia. A total of 94.22 Gb clean reads were obtained and assembled into 54,688 unigenes. A total of 224, 266, and 750 differently expressed genes were found in the comparison of the control and death groups, the control and moribund groups, and the control and survived groups, respectively. Three signal pathways closely related to hypoxia were found by enriching of the signal pathways in three comparison groups. In addition, much attention was focused on the differential genes in these pathways. Oxidative stress related genes, such as 70 kDa heat shock protein, phosphoenolpyruvate carboxykinase and cyclooxygenase were differentially expressed in different comparisons. After comparing with previous studies, cyclooxygenase was found to be an important hypoxia-related gene that is fully involved in the hypoxic response. Interestingly, two new genes with no Nr annotation were found in this manuscript. This manuscript will enrich our understanding of oxidative stress response to hypoxia and provide a theoretical basis for the subsequent solution of apoptosis caused by hypoxia.

RNA interference shows that Spook, the precursor gene of 20-hydroxyecdysone (20E), regulates the molting of Macrobrachium nipponense

The aim of this study was to explore the function of the Mn-Spook gene, which was found in the ovary transcriptome of the Oriental river prawn (Macrobrachium nipponense). The Spook gene, which is the precursor gene of 20-hydroxyecdysone (20E), plays an important role in the process of molting in many arthropods, but its function in M. nipponense is unclear. We cloned the full-length Mn-Spook gene from the ovary of M. nipponense and found that it had the same conserved domains as the P450 gene of the Halloween family of genes. The Mn-Spook gene was highly expressed in ovary and gill tissue during the breeding period. During ovarian development, Mn-spook gene expression was highest at the nearly-ripe stage, and it also was highly expressed in the zoea developmental stage. Cellular localization analysis showed that Mn-Spook signals accumulated in the cytoplasmic membrane and nucleus of oocytes. Finally, we used RNA interference to evaluate the function of the Mn-Spook gene. Compared with the control group, in vivo injection of Mn-Spook dsRNA effectively downregulated the expression of Mn-Spook and the content of 20E. The molting frequency of M. nipponense in the experimental group also was significantly inhibited. These results demonstrated that the Mn-Spook gene played an important role in the molting process of M. nipponense.

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

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

Identification and Characterization of the Succinate Dehydrogenase Complex Iron Sulfur Subunit B Gene in the Oriental River Prawn, Macrobrachium nipponense.

Previous studies have revealed that SDHB has potential functions in the male sexual differentiation and development in M. nipponense through providing ATP. In this study, the functions of Mn-SDHB were further analyzed in depth using quantitative polymerase chain reaction (qPCR), in situ hybridization, western-blot, and RNA interference (RNAi), combined with the histological observations. The full-genome sequence of Mn-SDHB was 54,608 bp at Chromosome 34, including 7 introns and 6 exons. The full-length cDNA sequence of Mn-SDHB was 1,268 base pairs (bp) long with an open reading frame of 807 bp, encoding for 268 amino acids. The highest expression level of Mn-SDHB in different tissues was observed in the testis, and male prawns at post-larval developmental stage 25 during different developmental stages, indicating that SDHB was potentially involved in the male sexual development in M. nipponense. In situ hybridization and western-blot analysis indicated that SDHB plays essential roles in the testis development. The in situ hybridization analysis also implies the potential roles of Mn-SDHB in ovarian development. The expressions of Mn-IAG were decreased after Mn-SDHB dsRNA injection, indicating SDHB has the positive regulatory effects on IAG in M. nipponese. Thus, SDHB was involved in the mechanism of the male sexual development. The testis development was inhibited, and sperms were rarely observed after 10 days of Mn-SDHB dsRNA injection, indicating SDHB has positive effects on the male sexual development in M. nipponense. This study highlights the functions of SDHB in M. nipponense, which provide new insights for the future studies of the male sexual development in other crustacean species.

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

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

Carbon budget in integrated aquaculture systems with Nile tilapia ( Oreochromis niloticus ) and Amazon river prawn ( Macrobrachium amazonicum )

This study was centred on the carbon budget of Integrated multitrophic aquaculture (IMTA) systems in earthen ponds stocked with the freshwater Amazon river prawn (Macrobrachium amazonicum) and Nile tilapia (Oreochromis niloticus), with or without different added substrates. The experimental design was completely randomized, with three treatments and four replicates. Carbon entered the system mainly through the diet (~58–63%), inlet water (~29–34%) and absorbed gases (~5–7%). Most of it was accumulated in the sediments (~42–70%) or discharged in the outlet water (~12–13%). The tilapias converted ~12% of the carbon available into harvested biomass, and the prawns converted only ~1%. The retention of carbon inside the ponds from the inlet water was ~1 tonne ha−1, and the atmosphere ~0.1–0.3 tonnes ha−1. The carbon accumulated in the sediment was about 3.5 tonnes ha-1. Data suggest that the integrated aquaculture in stagnant earthen ponds sequesters high quantities of carbon from the nutrient-rich source water and atmosphere, and the addition of substrates at 50% of pond area do not improve the assimilation of carbon by the farmed species, having a low effect on the carbon budget.

Impact of different dietary lutein levels on growth performance, biochemical and immuno-physiological parameters of oriental river prawn (Macrobrachium nipponense)

A 56-day trial was conducted to evaluate the effects of dietary lutein pigment on growth, biochemical, and immuno-physiological parameters of the oriental river prawn. Prawns were fed five formulated diets containing different lutein levels, 0 (control), 50, 100, 150, and 200 mg/kg. Growth performance, except hepatosomatic index, was affected by different lutein levels, and biochemical parameters (urea, uric acid, glucose, creatinine, and triglycerides) decreased. However, high-density and low-density lipoprotein elevated significantly compared to the control treatment. Furthermore, calcium, phosphorus, and cholesterol did not show a significant difference. Hemato-immunological parameters (albumin, total protein, cortisol, lysozyme, phenoloxidase, total hemocyte count, granular cells, semi-granular cells, hyaline cells, alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase), and hepatopancreatic antioxidant statuses (total antioxidant capacity, superoxide dismutase, catalase, and malondialdehyde), were significantly affected; however, alkaline phosphatase and glutathione peroxidase were not affected by lutein treatments. By increasing dietary lutein levels, digestive enzyme activities, total bacteria count, total carotenoid content, significantly increased. Conversely, lactic acid bacteria were not affected. Overall, the research results demonstrated that adding 200 mg/kg of lutein to the diet improved growth performance, biochemical and immuno-physiological parameters of the oriental river prawn.

A newly identified Hippo homologue from the oriental river prawn Macrobrachium nipponense is involved in the antimicrobial immune response

The Hippo signalling pathway plays a vital role in organ size control, cell proliferation, apoptosis, and immune regulation. In this study, a Hippo homologue with three isoforms (named MnHippo-a, MnHippo-b, and MnHippo-c) was isolated and characterized for the first time from the freshwater prawn Macrobrachium nipponense. The deduced amino acid sequences of MnHippo-a (698 aa), MnHippo-b (688 aa), and MnHippo-c (656 aa) were highly similar, and they all contained an N-terminal S_TKc (serine/threonine protein kinase catalytic) domain and a C-terminal Mst1_SARAH (Sav/Rassf/Hpo) domain. MnHippo-a and MnHippo-c were derived from alternative splicing. Phylogenetic analysis was performed, and the results revealed that MnHippo was a member of the clade containing STPK4 and Hippo of Penaeus vannamei. The expression distribution showed that MnHippo was constitutively expressed in various tissues of uninfected prawns and highly expressed in the hepatopancreas and intestine. In prawns challenged with Vibrio parahaemolyticus and Staphylococcus aureus, the expression of MnHippo in haemocytes was significantly upregulated. Furthermore, in MnHippo-knockdown prawns injected with V. parahaemolyticus or S. aureus, the transcription levels of five antimicrobial peptides were downregulated. MnHippo silencing weakened the clearance of V. parahaemolyticus and S. aureus in prawns. The survival rate of the MnHippo-dsRNA group was obviously decreased from 2 to 6 days post-injection with V. parahaemolyticus or S. aureus. Hence, MnHippo might be involved in the antibacterial immune defence of M. nipponense.

Comparison of morphology and genetic diversity between broodstock and hybrid offspring of oriental river prawn, Macrobrachium nipponense based on morphological analysis and SNP markers.

Hybridization is an effective method for the genetic improvement of farmed species. In this study, three broodstock populations (Changjiang, CJ, Dongting, DT, and Dianshan, DS) of oriental river prawn, Macrobrachium nipponense were used, and DS was used as the female broodstock. Through three-line hybridization, two hybrid populations were finally obtained. The F3 generation of the broodstock population and the F1 generation of the hybrid population were cultured indoors for 3 months. Through morphological analysis (cluster analysis, discriminant analysis and path analysis) it was found that the hybrid population and the broodstock had some differences, but not enough to reach the subspecies level, and the dominant traits exhibited differentiation and reorganization. This study identified SNP genetic markers, carried out systematic evolution analysis and genetic diversity analysis and found that the nucleotide diversity π and heterozygosity Het of the hybrid population were higher than those of the broodstock. Among broodstocks, the differentiation index (Fst ) of SCD and SDC was smallest (0.055). This research provides some valuable reference for genetic breeding.

Expression and functional analysis of cathepsin L1 in ovarian development of the oriental river prawn, Macrobrachium nipponense

Cathepsin L is an important member of the cysteine protease family and has a central role in the development of ovaries in insects and fish. In this study, we analyzed the characteristics of the cathepsin L1 gene in the female oriental river prawn, Macrobrachium nipponense. The cathepsin L1 cDNA was 1173 bp in length, including a 960 bp open reading frame that encoded 319 amino acids. The cathepsin L1 gene was classified into the cathepsin L group and named Mn-CTS L1 by phylogenetic analysis. qRT-PCR analysis indicated that Mn-CTS L1 was highly expressed in the hepatopancreas and ovaries of female prawns. During the different stages of ovarian development, Mn-CTS L1 expression in the hepatopancreas and ovaries peaked before ovarian maturation. Mn-CTS L1 expression was higher at the post-larval stage of day 15 than at other stages of embryogenesis. In situ hybridization studies revealed that Mn-CTS L1 was localized in the oocyte of the ovary. Injection of Mn-CTS L1 dsRNA significantly reduced Mn-CTS L1 expression and significantly increased the expression of vitellogenin. Changes in the gonad somatic index also confirmed the inhibitory effects of Mn-CTS L1 dsRNA. These results suggest that Mn-CTS L1 has a key role in ovarian development.

Growth, Production, and Feeding Efficiency of Freshwater, Longarm River Prawn Macrobrachium tenellum at Different Densities in Nursery Phase Culture under Intensive Conditions

AbstractThe aim of this study was to determine the effect of stocking density on growth performance, survival, feeding efficiency, and size distribution of the freshwater, longarm river prawn Macrobrachium tenellum during the nursery phase of intensive culture in a net cage–pond system. Juvenile longarm river prawns (mean weight = 0.46 g) were cultured in 12 net cages (1 m3) within two circular ponds (20.52 m3 each) at stocking densities of 50, 100, 200, and 400 prawns/m3. Final length, final body weight, weight gain, growth rate, and specific growth rate were found to be significantly better at a stocking density of 50 prawns/m3. A greater variation of sizes was observed at the density of 50 prawns/m3, with less in the highest density (400 prawns/m3). The results of the study showed that longarm river prawns in the nursery phase can be cultivated with a stocking density of 100 prawns/m3 to obtain a mean final weight of 1.6 g. This is the minimum size needed to obtain a high survival rate in the grow‐out stage in ponds. However, the best growth performance and survival were registered in the densities of 50 and 100 prawns/m3.

Effects of hydroponic supplementation on Amazon river prawn (Macrobrachium amazonicum Heller, 1862) and lettuce seedling (Lactuca sativa L.) development in aquaponic system

Studies about integrated farming of shrimp with vegetables are scarce, although productivity may be increased when supplemented with nutrients. Therefore, this study evaluated the effects of decreasing concentration of commercial hydroponic solution (treatments 0%, 20%, 46% and 100%) on water quality (nitrogen compounds, phosphate, conductivity, pH and dissolved oxygen), for Amazon river prawn, Macrobrachium amazonicum, and lettuce, Lactuca sativa, seedling development during 18 days. The hydroponic solution significantly increased the total ammonia and nitrate in rearing tanks, up to 60.4 ± 10.3 mg L−1 and 394 ± 53.7 mg L−1 (mean ± SEM) respectively at 100%. These toxic nitrogen levels and other components (trace elements) probably present in the solution decreased Amazon river prawn growth and survival by half when supplemented with 46% and 100%, respectively. Independently of the treatment in the first 14 days after sown, no significant change was observed in lettuce growth, however 18 days after sown with a 100% solution an increased number of leaves, height, fresh mass and plant length were observed. These results indicate that M. amazonicum waste may provide nutritional requirements for lettuce up to 14 days after sown, and afterward a nutrient should be added. We recommend supplementing water with a 20%-hydroponic solution to not affect development of the Amazon river prawn and to increase lettuce seedling growth.

Two genes related to reproductive development in the juvenile prawn, Macrobrachium nipponense: Molecular characterization and transcriptional response to nanoplastic exposure

Plastic pollution in the form of nanoplastics poses a global threat to aquatic ecosystems and the organisms inhabiting them. However, few studies have been conducted on the effects of nanoplastic exposure on reproductive development in crustaceans. In order to address this issue, juvenile oriental river prawns (Macrobrachium nipponense) were exposed to different concentrations of 75-nm polystyrene nanoplastics (0, 5, 10, 20, 40 mg/L) for 28 days. In order to study the regulation of reproduction-related genes in the presence of nanoplastics, the Wee1 protein kinase gene (Wee1) and OTU domain ubiquitin aldehyde binding protein gene (OTUB) were selected. In this study, for the first time, the full-length cDNA of Mn-Wee1 and Mn-OTUB were cloned from M. nipponense. Homologous alignments revealed that Mn-Wee1 had a highly conserved function-critical sequence, and that Mn-OTUB was more closely related to OTUB1 than OTUB2. With increasing concentration of nanoplastics, the expression of both genes increased initially, then decreased. The inhibition of expression of Wee1 and OTUB occurred in 40 mg/L group, respectively. Analysis of the data also indicated that nanoplastic exposure might have differing effects on gene expression in M. nipponense male and female reproductive organs.

External morphological stages and protein variations along with the embryonic development of the longarm river prawn Macrobrachium tenellum (Smith, 1871)

A good understanding of a given species' embryology is important to settle the larval rearing bases when juveniles are required for culture purposes or conservation programs. Changes in embryonic morphology, protein concentration, and protein type occurring in prawn eggs were analyzed in the present work. Berried females of Macrobrachium tenellum were collected in the Colotepec River, Oaxaca, Mexico. The eggs were taken from the ovigerous mass and embryonic stages classified by their color. Morphological changes in the embryos allowed identifying six embryonic stages based on color, egg size, and morphological features. Determinations of the protein extract were executed in SDS-PAGE (electrophoresis in polyacrylamide gels) and, subsequently, proteomic analyses were also performed. Protein bands along embryonic development and their molecular weights are presented and commented.