| Summary: | Marine mammals live a life of dual constraints and must balance energetic demands (oxygen consumption) and limited O2 availability while breath-holding. In order to overcome these dual constraints, marine mammals have developed unique physiological traits to cope with their aquatic environment, thereby taking advantage of a unique foraging niche. Extending breath-hold dive time increases the opportunity to obtain nutrients, but it can be energetically costly if marine mammals exceed the threshold for aerobic metabolism. We know relatively little about the physiological mechanisms employed by these animals that allow them to flourish in such an extreme environment. Due to the difficulty obtaining direct physiological measurements, there are gaps in knowledge for the field of diving physiology, particularly in the understanding of muscle perfusion during a dive. In order to improve our understanding of how marine mammals adjust muscle blood flow (oxygen and nutrients) during diving to increase dive time, we developed and tested a tag with oxygen sensors that attempted to measure O2 saturation in the muscle of freely deep-diving elephant seals. The purpose of this part of the study aimed at using an archival tag and implanted sensor system to measure physiological variables in freely deep-diving Northern elephant seals. Following the sensor and data logger development, we set out to test a long-held assumption that oximeter use in marine mammals could be calibrated with terrestrial mammal blood. This was of particular importance to this study as calibrations of the oximeter data loggers in the Northern elephant seal were needed. As part of the ability of marine mammals to prolong apnea for diving, some have modified hemoglobin to change its affinity for oxygen. These polymorphisms alter the affinity for O2, possibly by altering the folding of the protein. Alteration in the quaternary structure may also alter the optical properties of Hb. Oximeters use the change in the optical properties of oxygenated (HbO2) and ...
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