Transcriptome Analysis of Different Aquaculture Substrates on the Immune Response of Babylonia areolata

To assess the impact of different substrates in a recirculating water system on the immune response and antioxidant capacity of Babylonia areolata, we conducted a comparative analysis of the transcriptomes and antioxidant performance of the digestive glands in three substrate environments (sand-S group, ceramic granules-C group, and PVC breeding nest-P group). Transcriptome results revealed that the S group and P group exhibited the highest number of differentially expressed genes (DEGs), with a total of 2218 DEGs, including 928 upregulated and 1290 downregulated DEGs. The C group and P group had 1055 DEGs in common, with 316 upregulated and 739 downregulated DEGs. The C group and S group had the fewest DEGs, with 521 in total, including 303 upregulated and 218 downregulated DEGs. GO enrichment analysis showed that in the S vs P group, terms such as catalytic activity, membrane part, and cellular process were enriched with 287, 262, and 180 DEGs, respectively. In the C vs P group, binding, cellular process, and cell part were enriched with 146, 135, and 127 DEGs, respectively. In the C vs S group, catalytic activity, membrane part, and metabolic process were enriched with 90, 83, and 59 DEGs, respectively. Kegg enrichment analysis revealed significant changes in immune-related pathways in the S vs P group, including lysosome, phagosome, and leukocyte transendothelial migration, with 30, 13, and 10 enriched DEGs, respectively. In the C vs P group, phagosome, drug metabolism-other enzymes, and N-Glycan biosynthesis showed significant changes in immune-related pathways, with 9, 6, and 4 enriched DEGs, respectively. In the C vs S group, lysosome, PPAR signaling pathway, and fatty acid degradation exhibited significant changes in immune-related pathways, with 8, 4, and 3 enriched DEGs, respectively. Regarding antioxidant capacity, the S group showed significantly higher total T-AOC than the other experimental groups, while CAT, SOD, POD, and AKP were lower than in the C and P groups. The ACP level in the Sand group was not significantly different from the P group but significantly lower than the C group. In conclusion, substrate environments significantly influence the immune-related genes and key antioxidant enzyme activities in B. areolata.

Acute hypoxic exposure: Effect on hemocyte functional parameters and antioxidant potential in gills of the pacific oyster, Crassostrea gigas

Bivalve mollusks are frequently subjected to fluctuations of dissolved oxygen concentration in the environment which can represent a significant threat to bivalve antioxidant status. In this work the effects of hypoxia on hemocyte reactive oxygen species (ROS) production and level of mitochondrial potential as well as the activity and expression level of catalase (CAT) and superoxide dismutase (SOD) in gills of Crassostrea gigas were investigated after 24 h and 72 h exposure. 24 h hypoxia promoted an increase of mitochondrial membrane potential in agranulocytes and induced ROS accumulation in granulocytes. 72 h exposure substantially decreased hemocyte mitochondrial potential and intracellular ROS level in all hemocyte types. No significant changes in the activity of CAT in gills were observed following both 24 h and 72 h exposure periods compared to control. SOD activity in gills decreased after 72 h exposure to hypoxia but did not change under 24 h hypoxia. Significant up-regulation of SOD gene and no changes in expression level of CAT were observed in all experimental groups. The results indicate an overall shift in antioxidant status in gills and hemocytes of the Pacific oyster that may act as compensatory mechanisms to maintain redox homeostasis after a short-term (24 h) exposure and represent the occurrence of oxidative stress conditions at the end of 72 h hypoxia.