<b>Background and Objective:</b> The role of sediment in water bodies is significant because sediment can affect water quality and benthic organisms. This study investigated sediment\'s effect on the <i>Macrobrachium nipponense</i> population in the Anzali Lagoon. <b>Materials and Methods:</b> The samples were taken at three different sites of Anzali Lagoon in 2015. All the prawns cached by traps and sediment samples were taken exactly next to the traps. All samples were transported to the laboratory for analysis. Canonical correspondence analysis (CCA) was used to analyze the total catch for prawns across the sediment gradients measured. <b>Results:</b> It showed clear separation in all sites. Site 2 is more affected by clay; in Site 2, the number and the weight of <i>M. nipponense</i> were lower than in the other sites. In Sites 1 and 3, fine sand and medium sand were more affected, respectively. The results showed a relationship between the prawn population and sediment in the Anzali Lagoon. <b>Conclusion:</b> In some parts of the Anzali Lagoon, the quality and quantity of sediments were different, which directly affected the population of <i>M. nipponense</i>. Furthermore, because some parts of the lagoon are in good condition according to sediments and water quality, the Anzali Lagoon has a good potential for growing and living <i>M. nipponense</i>.

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.

Microplastics (MPs) have unique toxicokinetic (TK) processes that differ from those of soluble pollutants. This study investigated the ingestion, migration, accumulation, and clearance of environmental aging MPs in the Japanese swamp shrimp (Macrobrachium nipponense). The concentrations of plastic additives and personal care products adsorbed onto MPs in natural river water were determined, and TK models for MPs and MPs-loaded pollutants were developed. Results showed that the formation of surface biofilms and alterations in the distribution of MPs in waters caused by environmental aging affect MPs bioavailability, which is mainly related to the feeding habits of shrimp. The decrease in MPs particle size caused by biological digestion and the increase in the number of oxygen-containing functional groups caused by environmental aging affect the TK process of MPs. The TK model of MPs-loaded pollutants revealed the cleaning effect of shrimp on pollutants adsorbed onto MPs during swallowing and spitting MPs. This cleaning effect significantly increases the bioavailability of MPs-associated pollutants in aquatic environments. This study provides a new perspective for understanding the interactions between environmental MPs and their associated pollutants in aquatic ecosystems.

A new microsporidian disease of the pond-reared ridgetail white prawn, Palaemon carinicauda, was found in China. Light microscopy, pathology, and scanning electron microscopy showed that the parasite infected the host\'s skeletal muscle tissue and formed spherical sporophorous vesicles (SPOVs). Electron microscopy revealed that its merogonic life stages developed in direct contact with the host cytoplasm. The sporogonic life stages underwent octosporoblastic sporogony with the formation of eight uninucleate spores in each SPOV. Fresh SPOVs were 5.4 ± 0.55 µm in diameter. The octospores were oval and measured 2.3 × 1.5 μm (fresh) and 1.96 × 1.17 μm (fixed). The isofilar polar filament was coiled with 9-10 turns and arranged in two rows. Phylogenetic analysis based on the SSU rRNA gene suggests that this microsporidium has close affinities with members of the genera Potaspora and Apotaspora, but represents an independent generic taxon. We therefore propose the establishment of a new genus and species (Paospora carinifang n. gen., n. sp.) within the family Spragueidae. We also propose a taxonomic revision to transfer Potaspora macrobrachium to this new genus and reclassify it as Paospora macrobrachium comb. nov.

Signal theory predicts organisms should evolve signals that are conspicuous to intended receivers in natural signalling environments. Cleaner shrimps remove ectoparasites from reef fish clients and many signal their intent to clean by whipping long, white antennae. As white is a reliably conspicuous colour in aquatic environments, we hypothesized that selection has acted to increase broad-spectrum antennal reflectance in cleaners. Using scanning electron microscopy, optical models and reflectance measurements, we found that the antennae in three obligate cleaner species from two families (Palaemonidae and Lysmatidae) had thick (∼6 µm) chitinous layers or densely packed high refractive index spheres (300-400 nm diameter), which models show increase reflectance (400-700 nm). Two facultative and non-cleaning species had no visible antennae ultrastructure beyond the chitinous exoskeleton. Antennae reflectance was significantly higher in obligate cleaners than in facultative and non-cleaning species. Our results suggest that some obligate cleaners may have evolved ultrastructures that increase the conspicuousness of their antennae as signals.

Macrobrachium nipponense is an important commercial freshwater species in China. However, the ability of alkali tolerance of M. nipponense is insufficient to culture in the major saline-alkali water source in China. Thus, it is urgently needed to perform the genetic improvement of alkali tolerance in this species. In the present study, we aimed to analyse the effects of alkali treatment on gills in this species after 96 h alkalinity exposure under the alkali concentrations of 0 mmol/L, 4 mmol/L, 8 mmol/L, and 12 mmol/L through performing the histological observations, measurement of antioxidant enzymes, metabolic profiling analysis, and transcriptome profiling analysis. The results of the present study revealed that alkali treatment stimulated the contents of malondialdehyde, glutathione, glutathione peroxidase in gills, indicating these antioxidant enzymes plays essential roles in the protection of body from the damage, caused by the alkali treatment. In addition, high concentration of alkali treatment (> 8 mmol/L) resulted in the damage of gill membrane and haemolymph vessel, affecting the normal respiratory function of gill. Metabolic profiling analysis revealed that Metabolic pathways, Biosynthesis of secondary metabolites, Biosynthesis of plant secondary metabolites, Microbial metabolism in diverse environments, Biosynthesis of amino acids were identified as the main enriched metabolic pathways of differentially expressed metabolites, which are consistent with the previous publications, treated by the various environmental factors. Transcriptome profiling analyses revealed that the alkali concentration of 12 mmol/L has more regulatory effects on the changes of gene expression than the other alkali concentrations. KEGG analysis revealed that Phagosome, Lysosome, Glycolysis/Gluconeogenesis, Purine Metabolism, Amino sugar and nucleotide sugar metabolism, and Endocytosis were identified as the main enriched metabolic pathways in the present study, predicting these metabolic pathways may be involved in the adaption of alkali treatment in M. nipponense. Phagosome, Lysosome, Purine Metabolism, and Endocytosis are immune-related metabolic pathways, while Glycolysis/Gluconeogenesis, and Amino sugar and nucleotide sugar metabolism are energy metabolism-related metabolic pathways. Quantitative PCR analyses of differentially expressed genes (DEGs) verified the accuracy of the RNA-Seq. Alkali treatment significantly stimulated the expressions of DEGs from the metabolic pathways of Phagosome and Lysosome, suggesting Phagosome and Lysosome play essential roles in the regulation of alkali tolerance in this species, as well as the genes from these metabolic pathways. The present study identified the effects of alkali treatment on gills, providing valuable evidences for the genetic improvement of alkali tolerance in M. nipponense.

Tropomyosin (TM) is the main allergen of Macrobrachium nipponense. Recombinant allergens have great prospects in the detection, diagnosis, and treatment of food allergens. The purpose of this study was to compare the differences in structure and allergenicity between natural TM and recombinant TM. Recombinant TM of M. nipponense with a molecular weight of 38 kDa was successfully expressed in the Escherichia coli system. The amino acid sequence as well as secondary structure between natural and recombinant TM were similar, which were verified by mass and CD spectrometry, respectively. Studies showed that both natural TM and recombinant TM had strong allergenicity, and recombinant TM was more allergenic, which could be used as a substitute for natural TM in the diagnosis and treatment of shrimp allergy. This study provided stable and reliable allergen components for the detection of crustacean allergens and the diagnosis and treatment of food allergies caused by crustacean allergens.

The aim of this study was to evaluate the sensitivity of the prawn Palaemon argentinus to the pyrethroid cypermethrin (CYP) and the tetramic acid spirotetramat (STM). These treatments were compared with prawns collected at a reference site to define their basal physiological state. Initially, physicochemical parameters and several pollutants at the selected site were analyzed. The LC50-96 h was determined in adult prawns. Then, prawns were exposed for 96 h to sublethal concentrations of CYP (0.0005 μg/l) and STM (0.44 mg/l) to evaluate the effects on some biochemical endpoints. A treatment combining both pesticides was also added at 5 % of these values. Controls with and without solvent (acetone) were included. The LC50-96 h values were 0.005 μg/l and 4.43 mg/l for CYP and STM, respectively. Moreover, some biomarkers linked to oxidative and energy metabolism were analyzed in the hepatopancreas and muscle of both essayed prawns and those at the basal state. The STM caused a significant decrease in total protein content (32 %) in contrast to the increase of protein carbonyl content (71 %) (p < 0.05). Also, glutathione S-transferase (52 %) and catalase (61 %) activities in the hepatopancreas of exposed prawns were higher compared to both the control and state basal groups (p < 0.05). In muscle, only a significant decrease in the lactate content (69 %) was caused by STM (p < 0.05). In addition, CYP caused a significant increase in the lactate dehydrogenase activity (110 %) in muscle and triacylglycerol content (73 %) in the hepatopancreas (p < 0.05). The integrated biomarker index (IBRv2) analysis showed that STM caused greater damage than CYP. Besides, the combined treatment showed an antagonistic interaction between both insecticides. The differential response of biomarkers to both CYP and STM exposure with respect to their basal levels shows a high sensitivity of P. argentinus demonstrating its potential role as a bioindicator organism.

The Amazon prawn or Macrobrachium amazonicum (Heller, 1862) is widely distributed in South America, occurring in the Orinoco and Amazon rivers, and forms an important source of income for riverside families. This prawn hosts crustacean ectoparasites of the genus Probopyrus (Giard & Bonnier, 1888) (Bopyridae) that infest its gill cavity. The aim of the present study was to report new occurrences of Probopyrus in Amazon prawns caught in the Amazon River. Macrobrachium amazonicum prawns were collected between May 2017 and April 2018, and again from July 2021 to May 2022 in the regions of Ilha de Santana and Rio Mazagão, state of Amapá, Brazil. Among the 5,179 prawn specimens caught, 133 were parasitized by the ectoparasites Probopyrus pandalicola (Packard, 1879), Probopyrus bithynis (Richardson, 1904), Probopyrus floridensis (Richardson, 1904) and Probopyrus palaemoni (Lemos de Castro & Brasil Lima, 1974). These occurrences of P. floridensis and P. palaemoni in M. amazonicum were the first records of this on the northern coast of Brazil. These four ectoparasites are not limited to specific host species or genera, as observed in this study, which reports four species of Probopyrus infesting M. amazonicum.

Methyl farnesoate epoxidase (MFE) is a gene encoding an enzyme related to the last step of juvenile hormone biosynthesis. Mn-MFE cDNA has a total length of 1695 bp and an open reading frame (ORF) length of 1482 bp, encoding 493 amino acids. Sequence analysis showed that its amino acid sequence has a PPGP hinge, an FGCG structural domain, and other structural domains specific to the P450 family of enzymes. Mn-MFE was most highly expressed in the hepatopancreas, followed by the ovary and gill, weakly expressed in heart and muscle tissue, and barely expressed in the eyestalk and cranial ganglion. Mn-MFE expression remained stable during the larval period, during which it mainly played a critical role in gonadal differentiation. Expression in the ovary was positively correlated and expression in the hepatopancreas was negatively correlated with ovarian development. In situ hybridization (ISH) showed that the signal was expressed in the oocyte, nucleus, cell membrane and follicular cells, and the intensity of expression was strongest at stage O-IV. The knockdown of Mn-MFE resulted in a significantly lower gonadosomatic index and percentage of ovaries past stage O-III compared to the control group. However, no differences were found in the cumulative frequency of molting between the experimental and control groups. Moreover, the analysis of ovarian tissue sections at the end of the experiment showed differences between groups in development speed but not in subcellular structure. These results demonstrate that Mn-MFE promotes the ovarian development of Macrobrachium nipponense adults but has no effect on molting.