PATTERNS OF FORM AND FUNCTION IN DEVELOPING HEARTS - CONTRIBUTIONS FROM NONMAMMALIAN VERTEBRATES

Although most research on developmental cardiovascular physiology has focused on the bird embryo as a model for emulating developmental proc esses in mammals, there are increasingly compelling reasons to expand research to a variety of lower vertebrate systems. These reasons inclu de circumventing inherent limitations of the avian embryo and identify ing general vertebrate developmental patterns in the cardiovascular sy stem. In this paper, we first review data from hemodynamic studies on amphibians and birds (and what little exists from fish and reptiles), to provide a background against which lower vertebrate development can be examined. We then describe non-mammalian, non-avian paradigms for studying developmental patterns of vertebrate hearts. Developmental sp ects of cardiovascular performance, especially heart rate, blood press ure and cardiac output and how they change with ontogeny, are describe d for several amphibians and a few reptiles, identifying, where possib le, processes in common with birds and mammals. Finally, we indicate p roductive areas for future research with lower vertebrate cardiovascul ar systems, such as establishing ''critical windows'' for cardiovascul ar physiology during development, and determining the extent of develo pmental plasticity at the level of organ system physiology.