The morphology and physiology of crustacean cardiovascular systems has long been regarded as poorly organized and loosely controlled, systems serving only as a conduit to carry hemolymph. Current investigations of cardiovascular systems of decapod Crustacea have revealed an organization that is more complex than previously thought. The purpose of this research is to extend the study of crustacean cardiovascular physiology by investigating the hemodynamics of the freshwater crayfish, Procambarus clarkii, and the lobster, Homarus americanus. Crayfish and lobster were exposed to a P$\sb{\rm O\sb2}$ of 150 mmHg (control) followed by P$\sb{\rm O\sb2}$s of 25, 40, 75 and 115 mmHg O$\sb2$. Arterial hemolymph velocities were measured (Pulsed Doppler system) in the major arteries of crayfish and lobster. Hemolymph pressures were measured throughout the circulatory system of the crayfish. The cardiovascular response of hypoxic crayfish to injection of hyperoxic water into the branchial chamber was monitored to determine the location of O$\sb2$ receptors. Heart frequency in both species decreased as water P$\sb{\rm O\sb2}$ was lowered. Cardiac output was maintained in the crayfish due to an increase in stroke volume. Hemolymph flow increased to the anterior aorta only. Hemolymph pressures and ventilatory frequency increased down to a P$\sb{\rm O\sb2}$ of 50 mmHg O$\sb2$; below this all parameters declined. Cardiac output and stroke volume in the lobster were maintained down to a P$\sb{\rm O\sb2}$ of 75 mmHg O$\sb2$; at lower P$\sb{\rm O\sb2}$s cardiac output declined as a result of the hypoxia induced bradycardia. Hemolymph flow increased in the lateral arteries and ventral thoracic artery. Hypoxic crayfish showed a rapid increase in cardiovascular parameters (2.5 second) with a long lag in the respiratory response (75 seconds) to injection of hyperoxic water into their branchial chamber. Injection of hyperoxic water into animals that had defined gill sets removed indicates the presence of O$\sb2$-sensitive chemoreceptors in the posterior region of the branchial chamber. The redistribution of cardiac output in crayfish and lobster results in a maintenance of hemolymph flow to the anterior regions of the animals. The maintenance of cardiac output with hypoxia may not be solely related to maintaining M$\sb{\rm O\sb2}$, but may play a role in maintaining oxygen delivery to nervous tissue. The response to a declining water P$\sb{\rm O\sb2}$ is mediated by O$\sb2$ receptors associated with the posterior gills.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-6796 |
| Date | 01 January 1992 |
| Creators | Reiber, Carl Leonard |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
Page generated in 0.0061 seconds