Developmental physiology of the red swamp crayfish Procambarus clarkii
The primary goal of this research was to gain an understanding of the temporal sequence of cardiac regulatory mechanisms throughout the development of the red swamp crayfish Procambarus clarkii. Investigations focused on cardiac development and the ontogeny of the regulatory mechanisms of the cardiovascular system. Investigations concentrated on two areas: (1) the development of a staging scheme for P. clarkii, and (2) the ontogeny of neurohormonal regulation of the heart of P. clarkii. An embryonic staging scheme was established to allow a comparison between animals of the same "chronological-age" (fertilized at the same time), but not of the same developmental stage (morphological and physiological features compared). The staging scheme was established using embryos, noting only gross morphological and physiological landmarks that minimized trauma and invasion into the animal. Cardiovascular parameters (heart rate, stroke volume, and cardiac output) were determined throughout development by using a videomicroscopy technique and dimensional analysis. Heart rate, stroke volume, and cardiac output measured throughout development of the crayfish decreased significantly in late stage embryos, just prior to hatching. This decrease was thought to be due to an internal hypoxia experienced by the late stage embryo. When late stage embryos were exposed to hyperoxic water, heart rate increased significantly, suggesting that the decrease in cardiovascular parameters just prior to hatching is due to an internal hypoxia. To determine the stage at which components of the regulatory system come on-line, the temporal sequence of cardiac neurohormonal regulation was established by infusion of cardioactive drugs into the pericardial sinus of embryonic crayfish at defined developmental stages. (Abstract shortened by UMI.).
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