Effects of nanoplastic exposure on the immunity and metabolism of red crayfish (Cherax quadricarinatus) based on high-throughput sequencing.

Previous studies have shown that nanoplastics (NPs) are harmful pollutants that threaten aquatic organisms and ecosystems, however, less research has been conducted on the hazards of NPs for aquaculture animals. In this study, Cherax quadricarinatus was used as an experimental model to evaluate the possible effects of three concentrations (25, 250 and 2500 µg/L) of NPs on red crayfish. The toxicological effects of NPs on this species were investigated based on transcriptomics and microbiome. A total of 67,668 genes were obtained from the transcriptome. The annotation rate of the four major libraries (Nr, KEGG, KOG, Swissprot) was 40.17 %, and the functions of differential genes were mainly related to antioxidant activity, metabolism and immune processes. During the experiment, the activities of superoxide dismutase (SOD) and catalase (CAT) in the high concentration group were significantly decreased, while the concentration of malondialdehyde (MDA) increased after nanoplastics (NPs) exposure, and SOD1, Jafrac1 were significantly reduced at high concentrations. expression is inhibited. The immune genes LYZ and PPO2 were highly expressed at low concentrations and suppressed at high concentrations. After 14 days of exposure to NPs, significant changes in gut microbiota were observed, such as decreased abundances of Actinobacteria, Bacteroidetes, and Firmicutes. NPs compromise host health by inducing changes in microbial communities and the production of beneficial bacterial metabolites. Overall, these results suggest that NPs affect immune-related gene expression and antioxidant enzyme activity in red crayfish and cause redox imbalance in the body, altering the composition and diversity of the gut microbiota.

M1-type polarized macrophage contributes to brain damage through CXCR3.2/CXCL11 pathways after RGNNV infection in grouper.

The vertebrate central nervous system (CNS) is the most complex system of the body. The CNS, especially the brain, is generally regarded as immune-privileged. However, the specialized immune strategies in the brain and how immune cells, specifically macrophages in the brain, respond to virus invasion remain poorly understood. Therefore, this study aimed to examine the potential immune response of macrophages in the brain of orange-spotted groupers (Epinephelus coioides) following red-spotted grouper nervous necrosis virus (RGNNV) infection. We observed that RGNNV induced macrophages to produce an inflammatory response in the brain of orange-spotted grouper, and the macrophages exhibited M1-type polarization after RGNNV infection. In addition, we found RGNNV-induced macrophage M1 polarization via the CXCR3.2- CXCL11 pathway. Furthermore, we observed that RGNNV triggered M1 polarization in macrophages, resulting in substantial proinflammatory cytokine production and subsequent damage to brain tissue. These findings reveal a unique mechanism for brain macrophage polarization, emphasizing their role in contributing to nervous tissue damage following viral infection in the CNS.

Liposome-Encapsulated Rec8 and Dmrt1 Plasmids Induce Red-Spotted Grouper (Epinephelus akaara) Testis Maturation.

In fish, the maturity of gonads plays an important role in the development and reproduction of the population, and it also dictates the success of captive breeding. Therefore, finding ways to promote gonadal maturation is an important goal in aquaculture. In this study, we injected recombinant dmrt1 and rec8 overexpression plasmids packaged in liposomes into the immature testis of red-spotted grouper (Epinephelus akaara) and measured the expression of Dmrt1 and Rec8 protein in vivo. Gonadosomatic index (GSI) and gonadal histology analyses showed that the testis developed from the immature to the mature state within 7 days after plasmid injection. Additionally, the spermatozoa concentration and motility in plasmid-injected fish was the same as that of naturally mature fish. These results provided evidence that delivery of dmrt1 and rec8 expression plasmids into the testis via injection induced testis maturation in vivo.

Polystyrene nanoplastics affect digestive function and growth in juvenile groupers.

Polystyrene nanoplastics (PS-NPs) can impair antioxidant, immune, and nervous system functions as well as growth and development in aquatic organisms. At present, however, little is known about the effects and underlying mechanisms of PS-NPs on the digestive system of marine fish. Here, we studied the effects of these plastics on the intestinal health and growth performance of juvenile orange-spotted groupers (Epinephelus coioides). Based on histopathological analysis, we found that the liver and intestines can uptake PS-NPs at exposure concentrations of 300 and 3000 µg/ml, respectively. After 14 d of exposure, the activities of digestive enzymes lipase (LPS), trypsin (TRS), and lysozyme (LZM) were reduced, indicating that PS-NPs negatively affected digestive function in juvenile groupers. The PS-NPs also altered microbial community composition, resulting in a decrease in diversity and simplification of network relationships in the intestinal microbiota, but a significant increase in certain harmful bacteria, especially Vibrio and Aliivibrio. In addition, community assembly changed from being driven primarily by deterministic processes (68.89% for control group) to stochastic processes (73.33% and 51.11% for 300 and 3000 µg/ml PS-NP exposure groups, respectively). Furthermore, the specific growth rate (SGR) of the juvenile orange-spotted groupers decreased significantly with increasing PS-NP exposure concentrations (0.158% ± 0.032%, 0.095% ± 0.020%, and 0.074% ± 0.016% for 0, 300, and 3000 µg/L PS-NP groups, respectively). These results suggest that marine PS-NPs are harmful to the digestive system of juvenile fish and highlight the importance of evaluating the long-term impact of NPs in reshaping marine populations.