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No Food, No Drink, No Problem:

The Adaptations to Prolonged Fasting in the Northern Elephant Seal

Friday, November 6, 2009

Dr. Rudy M. Ortiz

Assistant Professor of Physiology & Nutrition

Founding Faculty

School of Natural Sciences

University of California, Merced

Northern elephant seal pups are naturally adapted to periods of prolonged fasting (2-3 mo) as an evolved component of their life history. Extended fasts of this duration in metabolically active animals are unrivaled amongst mammals and this situation provides a unique, natural experiment to elucidate the physiological mechanisms evolved by this group of mammals to alleviate the osmoregulatory burdens induced by such an extreme behavior. During this extended fasting period, the conservation of body water and electrolytes is critical to their survival, as protracted fasting periods are detrimental in other mammals. Our studies in this area have revealed that these animals have evolved robust renal mechanisms to abate the potential consequences of prolonged fasting and to conserve water and electrolytes. Some of these renal mechanisms appear to be independent of direct hormonal regulation while others are not. Furthermore, our studies involving exogenous manipulation of body water and plasma electrolytes provide significant insight to the regulation of these physiological components while animals are feeding at sea. My presentation will focus on these studies as we gain further insight to the physiological mechanisms these animals have evolved to adapt to their environment and to extreme conditions.