Nanoplastics (NPs) have emerged as contaminants in recent years and have attracted widespread attention because of their ecotoxicological effects. This study aimed to document the effects of different concentrations of NPs on the Monopterus albus. M. albus. M. albus were orally administered three different concentrations of 100 nm polystyrene NPs (0.05%, 0.5%, and 1% of the feed) for 35 days. The effects of different NPs concentrations on energy metabolism, enzyme biomarker responses, gene expression responses, and amino acid changes were investigated in M. albus after exposure. The results revealed that the gene expression of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase was up-regulated after the ingestion of high concentrations of NPs. The gluconeogenic pathway was inhibited, lactic acid (LA) content was increased, anaerobic glycolysis was used to produce LA to power the organism, and the accumulation of NPs led to a decrease in total cholesterol and triglyceride levels in liver tissues. There were increases in the relative liver content of glutamine, glycine, and methionine, which may be due to antioxidation in the liver. The stress may caused by NPs leads to the formation of some glutamylated amino acids, which are converted into glutathione to play an antioxidant role. NPs also induced lipotoxicity of the liver organoid by increasing lipid accumulation, these include methyl tetradecanoate (myristate), pentadecanoic acid, eicosanoic acid (arachidic acid), heptadecanoic acid (margaric acid), 5,8,11,14-eicosatetraenoic acid, and doconexent (Docosahexaenoic acid). Interestingly, some immune-related metabolites, such as 9-octadecenoic acid (oleic acid) and 9,12-octadecadienoic acid (linoleic acid), were significantly reduced, and these changes were probably caused by disturbances in hepatic lipid metabolism following NPs exposure.

Effects of dietary niacin on the growth performance, intestinal histomorphology, body composition, and antioxidant capacity were investigated in the present study to determine the optimum requirement of niacin for juvenile Eriocheir sinensis. All 360 crabs (initial average weight g) were randomly divided into 6 groups with 3 replicates in each group and 20 crabs in each replicate. Crabs were fed with the control diet (0.89 mg/kg) or niacin-supplemented diets (170.54 mg/kg, 347.05 mg/kg, 587.59 mg/kg, 784.85 mg/kg, and 1248.86 mg/kg) for 12 weeks (named as G1, G2, G3, G4, G5, and G6, respectively). The results showed that appropriate dietary niacin (above 347.05 mg/kg) significantly increased the weight gain rate (WGR) and specific growth rate (SGR) ( ), but did not affect the survival rate (SR), feed conversion ratio (FCR), daily feeding rate (DFR), and molting frequency (MF) of crabs ( ). The niacin content in the hepatopancreas of crabs in G1 and G2 was significantly lower than that of the other four groups ( ). Moreover, dietary niacin significantly affected the intestinal histomorphology of crabs, including the number of folds (NF), height of folds (HF), height of microvillus (HMV), and thickness of muscularis (TM) ( ). Additionally, moderate dietary niacin levels significantly affected the nonspecific immune responses of crabs, by improving the activity of catalase (CAT), glutathione s-transferase (GST), glutathione peroxidase (GSH-Px), and total superoxide dismutase (T-SOD) ( ). Based on the broken-line model analysis of SGR against dietary niacin level, the dietary niacin requirement of juvenile crabs was suggested to be 419.4 mg/kg.