Elasmobranch pericardial function. 3. The pericardioperitoneal canal in the horn sharkHeterodontus francisci |
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| Authors: | Daniel C Abel William R Lowelll Melody A Lipke |
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| Institution: | (1) Physiological Research Laboratory, A - 004, Scripps Institute of Oceanography, University of California, San Diego, La Jolla, CA, 92093, U.S.A.;(2) Department of Biological Sciences, Mary Washington College, Fredericksburg, VA, 22401, U.S.A.;(3) Present address: Department of Marine Science, Coastal Carolina University, P.O. Box 1954, Conway, SC, 29576 |
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| Abstract: | The pericardial and peritoneal spaces of elasmobranch fishes are connected by the pericardioperitoneal canal (PPC), which
allows pericardial fluid to escape when pressures exceed 0.1–0.3 kPA. Using the horn shark (Heterodontus francisci), we tested the hypothesis that the PPC functions to increase cardiac stroke volume by lowering pericardial pressure during
activity. We also assessed the role of the PPC during coughing, feeding, or burst swimming and examined the effects of PPC
occlusion. Increases in heart size were not prevented following augmented venous return in sharks with undisturbed or occluded
PCP, evidence that argues that pericardial fluid loss through the PPC is a cause of increased cardiac stroke volume and not
the result. Coughs, feeding, and burst swimming led to discharge of pericardial fluid. Chronic PPC occlusion resulted in an
increased pericardial pressure, fluid volume, and frequency of coughing, and a decreased survival time compared to shams.
Thus, in the horn shark the PPC likely compensates for constraints that may be imposed by the pericardium, provides a route
for pericardial drainage, and regulates cardiac stroke volume during periods of activity. |
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| Keywords: | elasmobranch heart Heterodontus pericardioperitoneal canal pericardium |
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