Biochemical, histological, and gene expression analysis in brain and heart in <i>Phoxinus lagowskii</i> under sustained and diel‐cycling hypoxia

Sustained and diel-cycling hypoxia frequently occurs in high-latitude environments; however, fish's biochemical, physiological, histological responses to these two conditions remain unknown. Current hypotheses posit that the heart brain of fish from high latitudes are integral their tolerance exhibit different response mechanisms cope with sustained hypoxic conditions. To test this, we acclimated Phoxinus lagowskii, a fish, ecologically relevant over 28 days. Histological analysis revealed changes relative thickness layers midbrain. There was prominent upsurge oxidative stress biomarkers (DCH) treatments, superoxide dismutase catalase activity. Our data suggested triglycerides were elevated DCH groups but remained unchanged regardless (SH) treatments. The majority enzyme activities (LDH, PK, PFK, HK) increased groups, especially at day 28. gene expression results indicated HIF mainly regulated long-term SH brain. Collectively, findings reveal P. lagowskii exhibits varied adaptation strategies exposure hypoxia.