Ontogeny of cardiovascular control in zebrafish (Danio rerio): effects of developmental environment.

The goal of this symposium paper was to identify and quantify developmental plasticity in the onset of cardiovascular responses in the zebrafish. Developmental plasticity was induced by altering the developmental environment in one of three ways: (1) by developing zebrafish in a constant current of 5 body lengths per second, (2) by developing zebrafish at a colder temperature (20 degrees C), and (3) by developing zebrafish in severe hypoxia (DO=0.8 mg/L). Early morphological development was significantly affected by each of the treatment environments with hypoxia slowing development the most and producing the highest variation in measurements. Development in constant water current did not significantly affect the timing onset of cardiovascular responses to the pharmacological agents applied. Development at 20 degrees C significantly delayed the onset of all cardiovascular responses measured by 2-3 days. Development in hypoxia, however, not only delayed onset of all cardiovascular responses, but also shifted the onset relative to the developmental program. Hypoxia clearly has a profound affect on the onset of cardiovascular regulation and it will take many more studies to elucidate the mechanisms by which hypoxia is having its effect. Furthermore, long term studies are also needed to assess whether the plasticity measured in this study is adaptive in the evolutionary sense.