Date of Award
© 2006 Lindsay Haupt (Murray-Miller)
A. Christine Brown
At certain upper and lower threshold temperatures (critical temperatures (Tc) crustaceans switch to anaerobic metabolism despite sufficient oxygen availability in the environment. I tested the hypothesis that failure of the heart at critical temperatures leads to insufficient oxygen delivery and subsequent anaerobiosis in peripheral tissues.
I exposed rock crabs, Cancer irroratus, as whole animals, and their buffer-perfused semi-isolated hearts to a progressive temperature increase, while monitoring heart rate and lactate accumulation. The whole animals heart rate increased with temperature following a Q10 of 2.8. An abrupt decline in heart rate occurred at 25°C and lactate accumulation occurred between 25°C and 30°C. The semi-isolated hearts followed a Q10 of only 1.2 during temperature increase. A second set of semi-isolated hearts were perfused and paced at a heart rate comparable to the whole animals at each temperature. The lactate concentration in the paced semi-isolated hearts did not significantly increase. AMPK activity and HSP70 levels were measured to investigate cellular changes occurring at Tc. Preliminary data suggests they are not good indicating parameters of Tc for isolated hearts.
I conclude that the whole animal’s Tc is 5°C lower than that of the heart muscle. Therefore, the onset of anaerobiosis in the peripheral tissues is not due to failure of the heart muscle. The processes within the whole animal that lead to anaerobiosis are set by other organ systems.
Haupt (Murray-Miller), Lindsay, "Temperature Tolerance In Crustaceans: Critical Temperatures And The Heart" (2006). All Theses And Dissertations. 3.