Effects of variations in hydrological connectivity on the macrobenthic community structure in reclaimed wetlands.

The Nanhui Dongtan Wetland is the most extensively reclaimed part of the Yangtze River Estuary wetland. In recent decades, urbanization has led to the extensive reclamation of the intertidal wetlands of Nanhui Dongtan. Macrobenthos are crucial as secondary production groups in the food web. However, there is a lack of in-depth research on the response mechanisms of macrobenthic communities to environmental disturbances in reclaimed wetlands. This study investigated the impact of hydrological connectivity changes caused by land reclamation on the macrobenthic community based on the macrobenthic community composition in preserved tidal flats and closed and open reclamation areas in Nanhui Dongtan. The results showed that the macrobenthos species richness in the closed reclamation area was significantly lower than that in the other areas. After dividing the functional groups of macrobenthos, structural equation modeling revealed a negative correlation between the salinity and the functional group composition. Analysis of the food sources revealed significant positive correlations between predatory and sediment-feeding populations and sediment organic matter content, between detritivorous group and environmental chlorophyll-a content, and between herbivorous group and suspended organic matter content in water. Therefore, variations in hydrological connectivity in different reclamation areas caused differences in food source distribution, which led to different compositions of macrobenthic functional groups. The results of this study provide a theoretical reference for the study of intertidal wetland habitat restoration.

Effects of Dietary 5-Aminolevulinic Acid on Growth, Nutrient Composition, and Intestinal Microflora in Juvenile Shrimp, Litopenaeus vannamei.

5-Aminolevulinic acid (5-ALA) is an endogenous non-protein amino acid and has been used as a new type of growth promoter in aquaculture feed. This study explored the effects of 5-ALA on growth and intestinal health in juvenile shrimp, Litopenaeus vannamei. Shrimps were fed diets containing five different 5-ALA levels (0, 15, 30, 45, and 60 g/t) for 90 days. A concentration of 45 g/t 5-ALA significantly improved growth metrics, including the specific growth rate, protein efficiency, and feed conversion (P < 0.05). The optimal concentration of 5-ALA was 38.3 g/t, as indicated by broken-line regression. Dietary supplementation with 5-ALA increased the crude protein content of whole shrimp, but had no significant effect on the moisture, ash, or crude lipid content (P > 0.05). Suitable supplementation of 5-ALA (45 g/t, 60 g/t) improved the activities of the digestive enzymes alpha-amylase, pepsin, trypsin, and lipase, thus promoting digestion and absorption. Shrimp fed with 45 g/t 5-ALA had increased levels of essential amino acids in the muscles and a higher proportion of polyunsaturated fatty acids in the hepatopancreas. Supplementation with 45 or 60 g/t 5-ALA upregulated the expression of genes related to growth and molting, including chitinase, ecdysone receptor, retinoic X receptor, calcium/calmodulin-dependent protein kinase I, heat shock protein 60, and heat shock protein 70. Moreover, dietary supplementation with 5-ALA affected the abundance of intestinal flora, increased the number of beneficial bacteria, and improved intestinal health. These results indicated that 5-ALA may significantly benefit shrimp health and aquaculture productivity, providing a novel theoretical basis for further research into 5-ALA as a dietary supplement.

Transcriptomic analysis reveals nanoplastics-induced apoptosis, autophagy and immune response in Litopenaeus vannamei.

Increasing attention is being paid to the toxic physiological effects of nanoplastics (NPs) on aquatic organisms. However, few studies have systematically evaluated the regulatory mechanisms of NPs on immune response in crustaceans. In this study, a 28-day chronic exposure experiment was conducted in which shrimps were exposed to various 80-nm polystyrene NPs concentrations (0, 0.1, 1, 5 and 10 mg/L). Transcriptomic analysis was used to investigate the regulatory mechanisms of NPs in immune response of Litopenaeus vannamei. With increasing NPs concentration, the total hemocyte count (THC) content decreased, while phagocytosis rate (PR) and respiratory burst (RB) showed trends of first rising and then falling. High concentration (10 mg/L) of NPs caused the destruction of hepatopancreas tissue structure, the shedding of microvilli, the increase number of hepatocyte apoptosis and autophagy structure. With increasing NPs concentration, the lysozyme (Lys), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities first increased and then decrease, while contents of lipid peroxidation and malondialdehyde increased; the expression levels of Toll, MyD88, GPx, SOD, proPO, Lys, and ALF generally increased at first and then decreased. Transcriptional sequencing analysis showed that the pathway of differentially expressed genes in KEGG enrichment mainly included lysosome (ko04142), apoptosis (ko04210) pathways, indicating that the NPs mainly affected the immune regulatory mechanism. Further analysis by Gene Set Enrichment Analysis (GSEA) showed that the up-regulation pathways of NPs activation mainly included immune response-related pathways such as mitochondrial autophagy, DNA repair, autophagosomes signaling pathway. Our results indicated that NPs exposure induced oxidative stress, apoptosis and autophagy in shrimps. This study provides a basis for further understanding of the mechanisms of antioxidant immune regulation by NPs in shrimp and may serve as a reference for healthy ecological culture of shrimp.

Effects of dietary 5-aminolevulinic acid on growth performance and nonspecific immunity of Litopenaeus vannamei, as determined by transcriptomic analysis.

5-aminolevulinic acid (5-ALA) is an endogenous non-protein amino acid that is frequently used in modern agriculture. This study set out to determine how dietary 5-ALA affected the nonspecific immunity and growth performance of Litopenaeus vannamei. The shrimp were supplemented with dietary 5-ALA at 0, 15, 30, 45, and 60 mg/kg for three months. Transcriptome data of the control group and the group supplemented with 45 mg/kg dietary 5-ALA were obtained using transcriptome sequencing. 592 DEGs were identified, of which 426 were up-regulated and 166 were down-regulated. The pathways and genes associated with growth performance and nonspecific immunity were confirmed using qRT-PCR. The highest survival rate, body length growth rate, and weight gain values were observed in shrimp fed diets containing 45 mg/kg 5-ALA. L. vannamei in this group had a significantly higher total hemocyte count, phagocytosis rate and respiratory burst value than those in the control group. High doses of dietary 5-ALA (45 mg/kg, 60 mg/kg) significantly increased the activities of catalase, superoxide dismutase, oxidized glutathione, glutathione-peroxidase, phenoloxidase, lysozyme, acid phosphatase, and alkaline phosphatase. At the transcriptional level, dietary 5-ALA significantly up-regulated the expression levels of antioxidant immune-related genes. The optimal concentration of 5-ALA supplementation was 39.43 mg/kg, as indicated by a broken line regression. Our study suggested that dietary 5-ALA positively impacts the growth and nonspecific immunity of L. vannamei, providing a novel theoretical basis for further research into 5-ALA as a dietary supplement.

Effects of stock enhancement on the macrobenthic community and ecological health in the intertidal zone of the estuarine wetland in Nanhui, China.

Nanhui Dongtan Wetland is an important part of Yangtze Estuary Wetland, and its species diversity has been affected by reclamation in recent years. To increase the diversity of species in reclamation areas, stock enhancement was implemented in the Nanhui Dongtan Wetland in May 2020 as a method of ecological restoration. We investigated macrobenthos before and after release, analysed changes in the macrobenthos and evaluated the ecological health of the sampled area. The diversity index showed species were more abundant and community structure were more diversified after release. Functional groups and redundancy analysis showed that the effects of stock enhancement on macrobenthos in Nanhui Dongtan wetland may be based on changes in secondary productivity. Stock enhancement may promote the resistance of macrobenthic communities to organic pollution without negatively affecting ecological health. As a method of ecological restoration, stock enhancement will play a positive role in the restoration of macrobenthic communities.

Effects of Dietary Melatonin on Antioxidant Capacity, Immune Defense, and Intestinal Microbiota in Red Swamp Crayfish (Procambarus clarkii).

The aim of this study was to investigate the effects of melatonin (MT) feed supplementation on the antioxidant capacity, immune defense, and intestinal flora in Procambarus clarkii (P. clarkii). Six groups of P. clarkii were fed test feeds containing different levels of MT: 0 mg/kg (control), 22.5, 41.2, 82.7, 165.1, and 329.2 mg/kg for a duration of 2 months. The specific growth rate, hepatosomatic index, and condition factor were recorded highest in the test group of shrimp fed an MT concentration of 165.1 mg/kg. Compared to the control group, the rate of apoptosis was lower in hepatopancreas cells of P. clarkii supplemented with high concentrations of MT. Analyses of antioxidant capacity and immune-response-related enzymes in the hepatopancreas indicated that dietary supplementation of MT significantly augmented both the antioxidant system and immune responses. Dietary MT supplementation significantly increased the expression levels of antioxidant-immunity-related genes and decreased the expression levels of genes linked to apoptosis. Dietary MT was associated with an elevation in the abundance of the Firmicutes and a reduction in the abundance of the Proteobacteria in the intestines; besides, resulting in an increase in the abundance of beneficial bacteria, such as Lactobacilli. The broken-line model indicated that the suitable MT concentration was 154.09-157.09 mg/kg. MT supplementation enhanced the growth performance of P. clarkii, exerting a positive influence on the intestinal microbiota, and bolstered both immune response and disease resistance. Thus, this study offered novel perspectives regarding the application of dietary MT supplementation within the aquaculture field.

Dietary lipid supplementation alleviated the impacts of polystyrene nanoplastic exposure in Litopenaeus vannamei.

The widespread occurrence of nanoplastic (NP) pollution in the environment is a growing concern, and its presence poses a potential threat to cultured aquatic animals. Previously, we found that NPs can significantly affect the lipid metabolism of shrimp. However, relevant reports about the effects of increasing dietary lipid levels on NP toxicity are lacking. Therefore, we explored the effects of dietary supplementation with different lipid levels on the growth and lipid metabolism of Pacific white shrimp (Litopenaeus vannamei). We cultured L. vannamei at three dietary lipid levels (3 %, 6 %, and 9 %) and three NP concentrations (0, 1, and 3 mg/L) for 2 months. We evaluated the effects of lipid levels on growth indexes, hepatopancreas morphological structure, lipid metabolism-related enzyme activity, and gene expression of the shrimp. The results showed that as lipid intake increased, the survival rate, body weight growth rate, and hepatosomatic ratio of the shrimp increased while the feed conversion rate decreased. Additionally, the crude protein and crude lipid contents increased, whereas the moisture and ash contents did not change much. We found that the morphological structure of the hepatopancreas was seriously damaged in the 3 mg/L NPs and 3 % dietary lipid group. Finally, lipid metabolism-related enzyme activities and gene expression levels increased with increased dietary lipid levels. Together, these results suggest that increasing dietary lipid content can improve shrimp growth and alleviate lipid metabolism disorders caused by NPs. This study is the first to show that nutrition regulation can alleviate the toxicity of NPs, and it provides a theoretical basis for the green and healthy culture of L. vannamei.

Exposure to polystyrene nanoplastics induces apoptosis, autophagy, histopathological damage, and intestinal microbiota dysbiosis of the Pacific whiteleg shrimp (Litopenaeus vannamei).

Nanoplastics (NPs) are widely distributed environmental pollutants that can disrupt intestinal immunity of crustaceans. In this study, the effects of NPs on gut immune enzyme activities, cell morphology, apoptosis, and microbiota diversity of Litopenaeus vannamei were investigated. L. vannamei was exposed to five concentrations of NPs (0, 0.1, 1, 5, and 10 mg/L) for 28 days. The results showed that higher concentrations of NPs damaged the intestinal villi, promoted formation of autophagosomes, increased intestinal non-specific immunoenzyme activities, and significantly increased apoptosis at 10 mg/L. In response to exposure to NPs, the expression levels of ATG3, ATG4, ATG12, Caspase-3, p53, and TNF initially increased and then decreased. In addition, the concentration of NPs was negatively correlated to the expression levels of the genes of interest and intestinal enzyme activities, suggesting that exposure to NPs inhibited apoptosis and immune function. The five dominant phyla of the gut microbiota (Proteobacteria, Firmicutes, Bacteroidetes, Acidobacteria, and Actinomycetes) were similar among groups exposed to different concentrations of NPs, but the abundances tended to differ. Notably, exposure to NPs increased the abundance of pathogenic bacteria. These results confirm that exposure to NPs negatively impacted intestinal immune function of L. vannamei. These findings provide useful references for efficient breeding of L. vannamei.

Polystyrene nanoplastics exposure alters muscle amino acid composition and nutritional quality of Pacific whiteleg shrimp (Litopenaeus vannamei).

Litopenaeus vannamei were exposed to 80-nm polystyrene nanoplastics (NPs) at different concentrations (0, 0.1, 1, 5, and 10 mg/L) for 28 days to study the effects on muscle nutritional quality. Our results showed that with increasing NPs concentrations, the survival rate, specific gain rate, and protein efficiency ratio decreased but the feed conversion ratio increased. There was no significant difference in moisture, ash, and crude lipid content in the muscle, and a general decrease in crude protein content was observed. However, the total amino acid and semi-essential amino acid contents decreased. The spacing between muscle fibers and the melting morphology of muscle increased. The hardness of muscle flesh texture increased, but springiness, cohesiveness, and chewiness decreased. Regarding antioxidant enzyme activity, the activity of catalase decreased, but the total antioxidant capacity, superoxide dismutase activity, and reduced glutathione first increased and then decreased. The expression level of the growth-related genes retinoid X receptor (RXR), chitin synthase (CHS), and calmodulin A (CaM) first increased then decreased, but calcium/calmodulin-dependent protein kinase I (CaMKI), ecdysteroid receptor (EcR), chitinase 5 (CHT5), cell division cycle 2 (Cdc2), and cyclin-dependent kinase 2 (CDK2) decreased. Our results suggest that exposure to NPs can inhibit growth by inducing oxidative stress, which leads to muscle tissue damage and changes in amino acid composition. These results will provide a theoretical reference for the risk assessment of NPs and the ecological health aquaculture of shrimp.

Effects of dietary melatonin on antioxidant and immune function of the Pacific white shrimp (Litopenaeus vannamei), as determined by transcriptomic analysis.

Melatonin (MT) is regarded as an antioxidant and immunostimulant that can efficiently scavenge free radicals and activate antioxidant enzymes. The aim of this study was to investigate the effects of dietary MT on the growth performance and immune function of the Pacific white shrimp (Litopenaeus vannamei). Six groups of L. vannamei were supplemented with dietary MT at 0, 22.5, 41.2, 82.7, 165.1, and 329.2 mg/kg levels for 2 months. RNA-Seq analysis was performed to obtain transcriptome data of the control group and the group supplemented with dietary MT at 82.7 mg/kg BW. In total, 1220 DEGs (799 up-regulated and 421 down-regulated) were identified. Pathways and genes related to growth performance and immune function were verified by real-time quantitative polymerase chain reaction. The total hemocyte count, phagocytosis rate, and respiratory burst were significantly increased in the MT (82.7 mg/kg BW) group as compared to the control group. Analysis of antioxidant-related enzymes in the hepatopancreas showed that dietary MT (82.7 mg/kg BW) significantly increased activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase, while dietary MT at 41.2 mg/kg BW significantly increased activities of glutathione S-transferase, lysozyme (LZM), and phenoloxidase (PO). At the transcriptional level, dietary MT up-regulated expression levels of genes associated with antioxidant immunity and growth, which included PO, SOD, LZM, GPx, chitin synthase, ecdysone receptor, calcium-calmodulin dependent protein kinase I, and retinoid X receptor. In conclusion, dietary MT may improve the growth performance and immune function of L. vannamei to some extent.

Transcriptomic analysis of the antioxidant responses and immunomodulatory effects of dietary melatonin in red swamp crayfish (Procambarus clarkii).

This study aimed to investigate the effects of dietary melatonin (MT) levels on the antioxidant capacity, immunomodulatory, and transcriptional regulation of red swamp crayfish. Six experimental diets with different levels of MT (0, 22.5, 41.2, 82.7, 165.1, and 329.2 mg/kg diet) were fed to juvenile crayfish for 60 d. The transcriptome data of the control group and the group supplemented with dietary MT at 165.1 mg/kg were obtained using RNA-seq. In total, 3653 differentially expressed genes (2082 up-regulated and 1571 down-regulated) were identified. Pathways and genes related to antioxidant immune and growth performance were verified by qRT-PCR. The total hemocyte count, phagocytosis rate, and respiratory burst were significantly increased in the MT (165.1 mg/kg) group compared to the control group. Analysis of antioxidant immune-related enzymes in the hepatopancreas demonstrated that dietary MT (165.1 mg/kg) significantly increased activities of catalase, superoxide dismutase, glutathione reductase, and glutathione peroxidase and significantly decreased aspartate aminotransferase and alanine aminotransferase activity. At the transcriptional level, dietary MT up-regulated expression levels of genes associated with antioxidant immune and development, which included toll-like receptors, Crustin, C-type lectin, and so on. To conclude, MT could be used as a supplement in crayfish feed to increase immunity and antioxidant capacity and according to the broken line regression, the ideal MT concentration was the 159.02 mg/kg. Overall, this study demonstrates the role of melatonin in the antioxidant responses and immunomodulatory of Procambarus clarkii, laying the foundation for the development of melatonin as a feed additive in the aquaculture of this species.

Comparative metabolomics analysis investigating the impact of melatonin-enriched diet on energy metabolism in the crayfish, Cherax destructor.

Melatonin is a multifunctional bioactive molecule present in almost all organisms and has been gradually used in the aquaculture industry in recent years. Energy metabolism is an essential process for individuals to maintain their life activities; however, the process through which melatonin regulates energy metabolism in aquatic animals remains unclear. The present study aimed to conduct a comprehensive analysis of the regulatory mechanism of melatonin for energy metabolism in Cherax destructor by combining metabolomics analysis with the detection of the key substance content, enzymatic activity, and gene expression levels in the energy metabolism process after culturing with dietary melatonin supplementation for 8 weeks. Our results showed that dietary melatonin increased the content of glycogen, triglycerides, and free fatty acids; decreased lactate levels; and promoted the enzymatic activity of pyruvate kinase (PK), malate dehydrogenase (MDH), and acetyl-CoA carboxylase. The results of gene expression analysis showed that dietary melatonin also increased the expression levels of hexokinase, PK, MDH, lactate dehydrogenase, lipase, and fatty acid synthase genes. The results of metabolomics analysis showed that differentially expressed metabolites were significantly enriched in lysine degradation and glycerophospholipid metabolism. In conclusion, our study demonstrates that dietary melatonin increased oxidative phosphorylation, improved glucose utilization, and promoted storage of glycogen and lipids in C. destructor. These lipids are used not only for energy storage but also to maintain the structure and function of cell membranes. Our results further add to the understanding of the mechanisms of energy regulation by melatonin in crustaceans.

Effects of ß-1,3-glucan on growth, immune responses, and intestinal microflora of the river prawn (Macrobrachium nipponense) and its resistance against Vibrio parahaemolyticus.

In this study, we investigated the impact of ß-1,3-glucan on the immune responses and gut microbiota of the river prawn (Macrobrachium nipponense) in the presence of Vibrio parahaemolyticus stress. Shrimps were fed one of the following diets: control (G1), 0.2% curdlan (G2), 0.1% ß-1,3-glucan (G3), 0.2% ß-1,3-glucan (G4), or 1.0% ß-1,3-glucan (G5) for 6 weeks and then challenged with V. parahaemolyticus for 96 h. Under Vibrio stress, shrimps in G4 exhibited the highest length gain rate, weight gain rate, and survival rate. They also showed increased intestinal muscle thickness and villus thickness compared to the control and 0.2% curdlan groups. The apoptosis rate was lower in G4 than in the control group, and the digestive enzyme activities (pepsin, trypsin, amylase, and lipase), immune enzyme activities (acid phosphatase, alkaline phosphatase, lysozyme, and phenoxidase), and energy metabolism (triglyceride, cholesterol, glycogen, and lactate dehydrogenase) were enhanced. Expression levels of growth-related genes (ecdysone receptor, calmodulin-dependent protein kinase I, chitin synthase, and retinoid X receptor) and immune-related genes (toll-like receptor 3, myeloid differentiation primary response 88, mitogen-activated protein kinase 7, and mitogen-activated protein kinase 14) were higher in G4 than in the control. Microbiota analysis indicated higher bacterial abundance in shrimps fed ß-1,3-glucan, as evidenced by Sob, Chao1, and ACE indices. Moreover, 0.2% ß-1,3-glucan increased the relative abundances of Bacteroidota and Firmicutes while reducing those of Corynebacteriales and Lactobacillales. In summary, ß-1,3-glucan enhances immune enzyme activities, alters immune-related gene expression, and impacts gut microbial diversity in shrimp. These findings provide valuable insights into the mechanisms underlying ß-1,3 glucan's immune-enhancing effects.

Dietary melatonin positively impacts the immune system of crayfish, Cherax destructor, as revealed by comparative proteomics analysis.

Melatonin, an indoleamine with various biological activities, is being used increasingly in the aquaculture industry for its broad immune effects. Cherax destructor is an emerging economically cultured crayfish that faces many problems in the breeding process. Previous work found that dietary melatonin has positive effects on the growth and immunity of C. destructor, but the specific mechanism involved remained unclear. In this study, proteomics was used to determine the mechanism of action of melatonin in C. destructor. Results showed that dietary melatonin resulted in decreased levels of hydrogen peroxide, alanine aminotransferase, and aspartate aminotransferase, but increased levels of glutathione peroxidase, acid phosphatase, and glutathione S-transferases. In total, 608 proteins were differentially expressed (418 upregulated and 190 downregulated), and were enriched in three main categories: innate immunity (B cell receptor signaling pathway and natural killer cell-mediated cytotoxicity), glucose metabolism (pentose phosphate pathway, pentose and glucuronate interconversions, and propionate metabolism), and amino acid metabolism (valine, leucine, and isoleucine degradation, and cysteine and methionine metabolism). In addition, dietary melatonin was also involved in the regulation of the mTOR signaling pathway, and upregulated the expression of genes encoding key factors, such as Ras-related GTP-binding protein A/B, eukaryotic initiation factor 4E, eukaryotic initiation factor 4E-binding protein, and p70 ribosomal S6 kinase. Overall, this study demonstrates the role of melatonin in the physiological regulation of C. destructor, laying the foundation for the development of melatonin as a feed additive in the aquaculture of this species.

Comparison of Growth Performance and Biochemical Components between Low-Salinity-Tolerant Hybrid and Normal Variety of Pacific White Shrimp (Penaeus vannamei).

Penaeus vannamei, a high-yield economical shrimp, is confronting germplasm degradation in the culture environments found in China, which results in a sharp drop in production. Genetic improvement by hybridization is an effective way to solve this problem. In this study, we selected the hybrid species adapted to low-salinity culture obtained by intraspecific crossing as the experimental group. The control group consisted of normal variety from the Hainan Lutai Company. The two groups of shrimps were cultured for three months under salinities of 1 PSU, 5 PSU, and 15 PSU. Growth-performance-related indicators, biochemical composition, and molting-related gene expression were examined. The results showed that at salinities of 1 PSU and 5 PSU, the survival rate and growth performance of the low-salt breeding group were better than those of the normal variety population. The digestive enzyme activity in the low-salt breeding group was higher, which was consistent with its better growth performance, and was also associated with higher triglyceride, total cholesterol, and glycogen content. Lower levels of lactic acid indicated less anaerobic metabolism and better adaptability to the environment. The amino acid and fatty acids analysis showed that levels of essential amino acids and high unsaturated fatty acids were both higher in the low-salt breeding group than in the normal variety shrimp cultured in a low-salinity environment. The expression levels of genes associated with molting (CHS, CaMKI, RXR, EcR, HSP60, and HSP70) were also higher in the low-salt breeding group than in the control group. The results indicated that the hybrid shrimp showed better growth performance and nutritional advantages compared with the normal shrimp under salinities of 1 PSU and 5 PSU. This research provides a valuable reference for subsequent genetic breeding and shrimp culture.

Effects of Salinity Stress on Histological Changes, Glucose Metabolism Index and Transcriptomic Profile in Freshwater Shrimp, Macrobrachium nipponense.

Salinity is an important factor in the aquatic environment and affects the ion homeostasis and physiological activities of crustaceans. Macrobrachium nipponense is a shrimp that mainly lives in fresh and low-salt waters and plays a huge economic role in China's shrimp market. Currently, there are only a few studies on the effects of salinity on M. nipponense. Therefore, it is of particular importance to study the molecular responses of M. nipponense to salinity fluctuations. In this study, M. nipponense was set at salinities of 0, 8, 14 and 22‱ for 6 weeks. The gills from the control (0‱) and isotonic groups (14‱) were used for RNA extraction and transcriptome analysis. In total, 593 differentially expressed genes (DEGs) were identified, of which 282 were up-regulated and 311 were down-regulated. The most abundant gill transcripts responding to different salinity levels based on GO classification were organelle membrane (cellular component), creatine transmembrane transporter activity (molecular function) and creatine transmembrane transport (biological function). KEGG analysis showed that the most enriched and significantly affected pathways included AMPK signaling, lysosome and cytochrome P450. In addition, 15 DEGs were selected for qRT-PCR verification, which were mainly related to ion homeostasis, glucose metabolism and lipid metabolism. The results showed that the expression patterns of these genes were similar to the high-throughput data. Compared with the control group, high salinity caused obvious injury to gill tissue, mainly manifested as contraction and relaxation of gill filament, cavity vacuolation and severe epithelial disintegration. Glucose-metabolism-related enzyme activities (e.g., pyruvate kinase, hexokinase, 6-phosphate fructose kinase) and related-gene expression (e.g., hexokinase, pyruvate kinase, 6-phosphate fructose kinase) in the gills were significantly higher at a salinity of 14‱. This study showed that salinity stress activated ion transport channels and promoted an up-regulated level of glucose metabolism. High salinity levels caused damage to the gill tissue of M. nipponense. Overall, these results improved our understanding of the salt tolerance mechanism of M. nipponense.

Haloxyfop-P-methyl induces immunotoxicity and glucose metabolism disorders and affects the Nrf2/ARE pathway mediated antioxidant system in Chiromantes dehaani.

Haloxyfop-P-methyl is used extensively in agricultural production, and its metabolites in soil have potentially toxic effects on aquatic ecosystems. In this study, we explored the toxicity of haloxyfop-P-methyl on Chiromantes dehaani. The results of the 21-day toxicity test showed that haloxyfop-P-methyl decreased the weight gain (WG), specific growth rate (SGR) and hepatosomatic index (HSI). In glucose metabolism, haloxyfop-P-methyl reduced pyruvate, lactate, lactate dehydrogenase and succinate dehydrogenase, but enhanced glucose-6-phosphate dehydrogenase and hexokinase. Furthermore, expression of glucose metabolism-related genes was upregulated. We cloned the full-length CdG6PDH gene, which contains a 1587 bp ORF that encoded a 528 amino acid polypeptide. In antioxidant system, haloxyfop-P-methyl increased glutathione, thioredoxin reductase and thioredoxin peroxidase activities and activated the Nrf2/ARE pathway through upregulation of ERK, JNK, PKC and Nrf2. In immunity, low concentrations haloxyfop-P-methyl, or short-term exposure, upregulated the expression of immune-related genes and enhanced immune-related enzymes activity, while high concentrations or long-term exposure inhibited immune function. In summary, haloxyfop-P-methyl inhibited the growth performance, disrupted glucose metabolism, activated the antioxidant system, and led to immunotoxicity. The results deepen our understanding of the toxicity mechanism of haloxyfop-P-methyl and provide basic biological data for the comprehensive assessment of the risk of haloxyfop-P-methyl to the environment and humans.

A Simulation of Thermal Management Using a Diamond Substrate with Nanostructures.

In recent years, the rapid progress in the field of GaN-based power devices has led to a smaller chip size and increased power usage. However, this has given rise to increasing heat aggregation, which affects the reliability and stability of these devices. To address this issue, diamond substrates with nanostructures were designed and investigated in this paper. The simulation results confirmed the enhanced performance of the device with diamond nanostructures, and the fabrication of a diamond substrate with nanostructures is demonstrated herein. The diamond substrate with square nanopillars 2000 nm in height exhibited optimal heat dissipation performance. Nanostructures can effectively decrease heat accumulation, resulting in a reduction in temperature from 121 °C to 114 °C. Overall, the simulation and experimental results in this work may provide guidelines and help in the development of the advanced thermal management of GaN devices using diamond micro/nanostructured substrates.

Integrated physiological and transcriptome analysis reveals potential toxicity mechanism of haloxyfop-P-methyl to Chiromantes dehaani.

Haloxyfop-P-methyl is widely used in controlling gramineous weeds, including the invasive plant Spartina alterniflora. However, the mechanism of its toxicity to crustaceans is unclear. In this study, we adopted transcriptome analysis combined with physiologic changes to investigate the response of estuarine crab (Chiromantes dehaani) to haloxyfop-P-methyl. The results showed that the median lethal concentration (LC50) of C. dehaani to haloxyfop-P-methyl at 96 h was 12.886 mg/L. Antioxidant system analysis indicated that MDA, CAT, GR, T-GSH, and GSSG might be sensitive biomarkers that characterize the oxidative defense response of the crab. In total, 782 differentially expressed genes were identified, including 489 up-regulated and 293 down-regulated genes. Glutathione metabolism, detoxification response and energy metabolism were significantly enriched, revealing the potential toxic mechanism of haloxyfop-P-methyl to C. dehaani. These results provide a theoretical foundation for further research on haloxyfop-P-methyl toxicity to crustaceans.

Effects of dietary melatonin on growth performance, antioxidant capacity, and nonspecific immunity in crayfish, Cherax destructor.

Melatonin (MT) is an indole hormone widely found in plants and animals. Many studies have shown that MT promotes the growth and immunity of mammals, fish, and crabs. However, the effect on commercial crayfish has not been demonstrated. The purpose of this study was to evaluate the effects of dietary MT on growth performance and innate immunity of Cherax destructor from three aspects of individual level, biochemical level, and molecular level after 8 weeks of culture. In this study, we found that MT supplementation increased weight gain rate, specific growth rate, and digestive enzyme activity in C. destructor compared to the control group. Dietary MT not only promoted the activity of T-AOC, SOD, and GR, increased the content of GSH, and decreased the content of MDA in the hepatopancreas, but also increased the content of hemocyanin and copper ions and AKP activity in hemolymph. Gene expression results showed that MT supplementation at appropriate doses increased the expression of cell cycle-regulated genes (CDK, CKI, IGF, and HGF) and non-specific immune genes (TRXR, HSP60, and HSP70). In conclusion, our study showed that adding MT to the diet improved growth performance, enhanced the antioxidant capacity of hepatopancreas, and immune parameters of hemolymph in C. destructor. In addition, our results showed that the optimal dietary supplementation dose of MT in C. destructor is 75-81 mg/kg.