DEAROLF, J.L.*; MCLELLAN, W.A.; PABST, D.A.; HERMANSON, J.W.; Hendrix College, Conway, AR; University of North Carolina at Wilmington; University of North Carolina at Wilmington; Cornell University, Ithaca, NY: Metabolic development of the diaphragm of bottlenose dolphins (Tursiops truncatus)

Neonatal bottlenose dolphins (Tursiops truncatus) breathe more frequently than adults, and therefore, their diaphragms must be prepared to sustain repetitive, relatively frequent contractions from the instant of birth. This study investigated the metabolic preparedness of the neonatal dolphin diaphragm by comparing neonatal levels of oxidative enzymes (NADH and SDH) as well as the concentration of myoglobin ([Mb]) to those found in the muscle of adults. Histochemical and biochemical measures of oxidative enzyme activity levels revealed that the neonatal dolphin had greater activity levels in its diaphragm than what was exhibited by the adult diaphragm. In contrast, the neonatal diaphragm only contained 30% of the adult [Mb]. However, this value was greater than that seen in their locomotor muscles (10-19%). Diaphragmatic [Mb] was also found to increase with total body length, a relationship that may be correlated with the onset of breath-hold diving in dolphins. Therefore, the dolphin diaphragm is metabolically prepared to support the increased ventilation rates of neonates. In addition, this muscle can increase its [Mb] to match the needs of the young dolphin as its diving abilities mature, a pattern that is also exhibited by their locomotor muscles.