Impact of Marine Heatwaves on Carcinus maenas Crabs: Physiological and Biochemical Mechanisms of Thermal Stress Resilience

Marine heatwaves (MHWs), characterized by prolonged periods of elevated sea temperatures, pose significant threats to marine ecosystems, particularly affecting the physiology and behavior of marine organisms, including crustaceans. This study investigates the physiological and biochemical responses of males and females of Carcinus maenas crabs, after an acute exposure to an MHW, focusing on energy metabolism, oxidative status, and potential neurotoxicity. Specimens were exposed to controlled laboratory conditions simulating a temperature increase from 17 °C to 23 °C, and responses were analyzed in gills and hepatopancreas. Results revealed sex-specific differences in thermal stress resilience, with males showing higher glycogen storage in gills after MHW exposure, while females exhibited a significant reduction in glycogen reserves and an increase in antioxidant enzyme activity. Superoxide dismutase and glutathione reductase activities were notably elevated in females subjected to MHW, suggesting a more robust antioxidant response to counteract oxidative stress. Additionally, acetylcholinesterase activity, an indicator of neurotoxicity, was significantly reduced in females post-MHW, hinting at potential neurotoxic effects. Despite these biochemical changes, lipid peroxidation levels remained stable across both sexes and tissues, indicating that short-term MHW exposure did not cause significant oxidative damage to cell membranes. This study highlights the importance of considering sex differences in assessing the impacts of climate change-induced stressors on marine organisms, as males and females display distinct metabolic and physiological strategies for coping with thermal stress.