Central arterial hemodynamics in larval bullfrogs (Rana catesbeiana): Developmental and seasonal influences

grative Comp. Physiol. 29): R240-R246,1991.-Central arterial hemodynamics (blood pressure and velocity) as a function of ontogeny and season were determined in larval Rana cates-beiana (body mass 0.3-8.7 g, 20-22°C). Ventricular systolic pressure increased from 1.8 mmHg at stage (St) II to 11.9 mmHg at St XIII, while ventricular diastolic pressures usually were cl.0 mmHg. In early stages (up to St V-VII) of fall/winter larvae, the pressure waveform in the conus arteriosus was often biphasic. The first peak was due to weak ventricular contraction (sometimes inadequate to eject blood into the arterial tree), and a stronger second peak resulted from conal contraction. In these young fall/winter larvae, the conus-not the ventricle-was the major circulatory pump. Older larvae (>St X) showed “adultlike ” central hemodynamics, with the ventricle ejecting blood through the conus into the central arterial circulation