Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: Natural heartbeat patterns of six ascidians and environmental effects on cardiac function in Clavelina huntsmani
Student Author(s): Ponec, Robert J.
Faculty Advisor(s): Gilly, William F.
Pages: 33
Location: Final Papers Biology 175H
Date: June 1981
Keywords: ascidians
Abstract: 1. The bidirectional hearts of the tunicates Ascidia ceratodes, Ciona intestinalis, and Clavelina huntsmani showed preferred directionality in number, rate, and period of beating. 2. Each species tested demonstrated a characteristic reversal pattern, but there were large individual variations from the species averages. 3. Temperature affected both rate and period of beating, but it did not affect number beats per period. 4. Salinity changes and injury had significant effects on the cardiac function of Clavelina huntsmani. Changes in the pH had no effect. 5. Heart reate slowed just before reversal in all six species tested. 6. There are at least five different types of heartbeat reversal. 7. An endogenous counting mechanism seems to be a major means of regulating reversal.