THERMAL INFLUENCE ON METABOLIC RATES AND A BIOENERGETIC BUDGET FOR NOTOPHTHALMUS-VIRIDESCENS FROM SOUTHWESTERN MASSACHUSETTS

Notophthalmus viridescens has been reported to overwinter on land in s outhwestern Massachusetts, whereas these newts hibernate in water in s outhern Ohio. Aquatic and terrestrial metabolic rates of newts from Ma ssachusetts were measured at different exercise speeds and acclimation temperatures in order to better understand their seasonal energetic b udgets. Oxygen uptake at 25 degrees C increased with increased swimmin g and walking speeds and reached a plateau at speeds of 60 and 90 cm/m in, whereas at 5 degrees C, oxygen consumption linearly increased with swimming speeds. Aerobic transport costs of the newts thus decreased with increased locomotor speeds at 25 degrees C but remained unchanged when the newts were exercised in water at 5 degrees C. Anserobic meta bolic rates of the newts on land were little affected by acclimation t emperature but also increased linearly with walking speeds at both 5 d egrees C and 25 degrees C. Anaerobiosis contributed most of the energy for the locomotion of the newts. These newts stored an average of 12 mg lipd/g body mass, which could apparntly support their survival at 5 degrees C for 46 days without food on land but only for 18 days in wa ter. These calculations, based on measured metabolic rates and energy reserves, support field observations of red-spotted newts hibernating on land in Massachusetts.