Ecophysiology and Behavioral Indicators of thermal Stress in Freshwater Crab Himalayapotamon emphyseteum Under Experimental Warming.

Global warming poses substantial challenges to ectothermic organisms, which depend on physiological and behavioural adjustments to maintain homeostasis under thermal stress. We examined the effects of experimental warming on oxygen consumption, ammonia excretion, feeding activity, surface activity, burrow retreat, and critical thermal maximum (CTMax) in Himalayapotamon emphyseteum. Crabs were exposed to three independent experimental temperatures (27, 31, and 33°C), and physiological and behavioural responses were assessed. Oxygen consumption rate increased significantly with temperature, from 1.917±0.192 mg O₂ g⁻¹ h⁻¹ at 27°C to 3.606±0.631 at 31°C and 5.835±0.792 at 33°C (p<0.001). Ammonia excretion did not differ between 27 and 31°C but increased significantly at 33°C (p<0.001). Feeding rate and surface activity decreased significantly with increasing temperature, whereas burrow retreat increased significantly (p<0.001). CTMax was strongly affected by heating rate, increasing from 32.90±0.88°C at 1°C min⁻¹ to 34.10±0.74°C at 1°C per 30 min and 35.90±0.32°C at 1°C h⁻¹ (p<0.001). Experimental warming elicited pronounced physiological and behavioural responses, while measured upper thermal limits were strongly influenced by heating rate and experimental protocol.Reduced feeding and surface activity, increased burrow retreat, and elevated metabolic rate indicate significant physiological and behavioral responses to warming.