Gianfranco Santovito (2025) CAN ANTARCTIC FISH FACE MARINE HEATWAVE-LIKE EVENTS? EXPLORING CARDIAC PHYSIOLOGY OF TREMATOMUS BERNACCHII USING BIO-LOGGERS AND STRESS BIOMARKERS.

Rising seawater temperatures fundamentally reshape marine ecosystems, with the Southern Ocean exhibiting heightened vulnerability to climatic perturbations. Antarctic teleosts have evolved under near-constant sub-zero conditions, developing unique physiological adaptations. In this study, we investigated the responses of Trematomus bernacchii, an endemic Antarctic fish, to three successive marine heatwave-like events. Using state-of-the-art implantable bio-loggers, we continuously monitored core body temperature and heart rate over 15 days, revealing a statistically significant positive correlation between internal temperature and cardiac performance, increasing by approximately 25% per °C. Molecular analyses of cardiac tissue revealed a novel sequential antioxidant response. An early upregulation of gpx4 suggests immediate mitochondrial protection against lipid peroxidation, while subsequent induction of gpx1, prdx3, and prdx5 indicates a broader cytosolic defence. Furthermore, the marked decoupling between elevated gpx1 transcript levels and diminished Selenium-dependent glutathione peroxidase enzymatic activity highlights a hitherto unrecognised post-transcriptional regulatory mechanism under acute thermal stress. Our findings suggest that T. bernacchii activates a sequential, organ-specific stress response to short-term warming, which may allow it to overcome episodic heatwaves.