Meeting Abstract

61.5  Friday, Jan. 6  Cardiovascular plasticity during hypoxic development in reptile embryos EME, J*; TATE, KB; KOHL, ZF; SLAY, CE; HICKS, JW; CROSSLEY II, DA; U N Texas; U N Texas; U N Texas; U Cal Irvine; U Cal Irvine; U N Texas

The cardiovascular (CV) system is the first operational organ system, but little is known about variation in CV regulatory maturation across the vertebrate evolutionary tree. In particular, reptiles are an understudied group that represents evolutionary intermediates between water-breathing vertebrates and endothermic, air-breathing tetrapods (birds and mammals). Reptile eggs, and presumably the ancestors of birds and mammals, incubate without maternal care and are subject to environmental stressors during development. One stressor is reduced micro-environmental oxygen content, and we have shown that this stress impacts reptilian CV function and maturation. Using two reptiles, Snapping turtles and American alligators, we investigated in ovo species differences in maturation and function of the CV system following chronic incubation in hypoxia (10% O2). Hypoxia alters the tonic regulation of baseline CV variables, and results in relative cardiac enlargement. Assessment of CV reflexes induced via acute hypoxia or pharmacological stimuli indicate reflexes can be plastic and blunted by chronic hypoxic incubation. However, turtle and alligator embryos exhibit different patterns of CV maturation during development. Alligator embryos possess an adrenergic tone originating from circulating catecholamines only, and cholinergic tone is not present until just prior to hatchling. Turtle embryos display cholinergic tone at 70% of development, and rely on autonomic tone to control heart rate over the last 30% of incubation. Our data indicate that maturation of CV function exhibits phenotypic plasticity in response to hypoxic incubation in both species, and that turtle embryos display a more ‘advanced’ developmental program than alligator embryos. NSF CAREER IBN IOS-0845741 to DAC