In marine ecosystems, temperature regulates the energy metabolism of animals. In the last decades, the temperature increase was related to mass mortality events of marine ectotherms, particularly during high-energy investment for reproduction. In scallops, the mantle has been poorly investigated while this tissue covers more than 40 % of the body mass, contributing to the perception of surrounding environmental stimuli. Our aim was to assess the cellular and molecular responses linked to energy metabolism in the mantle of adult N. subnodosus facing acute hyperthermia during reproductive effort. Scallops collected in spring (late gametogenesis) and summer (ripe gonads) were exposed to a control temperature (22 degrees C) or acute hyperthermia (30 degrees C) for 24 h. In spring, increased arginine kinase (AK) activity together with increased pyruvate kinase/citrate synthase ratio (PK/CS) suggested an enhanced carbohydrate, pyruvate, and arginine metabolism to maintain the adenylate energy charge (AEC) in the mantle of scallops coping with acute thermal increase. In summer, animals decreased their AEC (5 %) and arginine phosphate pool (40 %) and increased their anaerobic metabolism as shown by enhanced activities of lactate-dehydrogenase (LDH) and octopine dehydrogenase (ODH), respectively. The abundance of twenty proteins involved in energy metabolism (isocitrate dehydrogenase, ATP synthase subunit beta), protein protection (cognate heat shock protein 70), and cytoskeleton (actins and tubulins) were affected only by season. These results underlie the role of the mantle of N. subnodosus in the seasonal responses of this tissue to thermal fluctuations during reproductive effort with possible implications for the physiological performance of scallops under heat waves in wild or harvest conditions.