The effects of sustained and diel-cycling hypoxia on high-latitude fish Phoxinus lagowskii

High-latitude fish are subjected to sustained and diel-cycling hypoxia. Oxygen deficiency could pose a serious threat to fish, but little information is available regarding the response mechanisms employed by high-latitude fish to sustained and diel-cycling hypoxia. In this study, a combination of transcriptomics and metabolomics were used to examine the molecular response mechanisms actioned by sustained and diel-cycling hypoxia in the high-latitude fish, Phoxinus lagowskii. P. lagowskii was divided into normoxic control (6.0-7.0 mg/L dissolved oxygen), sustained (1.5 mg/L dissolved oxygen), and diel-cycling hypoxic treatment (6.0-7.0 mg/L between 07:00-21:00, and 3.0-4.0 mg/L between 21:00-07:00) tanks for 28 days. Differentially expressed genes (DEGs) and significantly different metabolites (DMs) related to digestive proteases, lipid metabolism, estrogen signaling pathway, steroid hormone biosynthesis, glutathione metabolism, and tryptophan metabolism were identified from comparative metabolomic and transcriptomic data expression profiles within the liver. The current study found that P. lagowskii had significantly different responses between sustained and diel-cycling hypoxia. P. lagowskii faced with sustained hypoxia may enhance their tolerance capacity through phospholipid and glutathione metabolism. Our data provide new insights into the high latitude fish coping with changes in hypoxia and warrants further investigation into these potentially important genes and metabolites.