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Effects Of Temperature, Epinephrine And Ca2+ On The Hearts Of Yellowfin Tuna (Thunnus Albacares), Jason M. Blank, Jeffery M. Morrissette, Peter S. Davie, Barbara A. Block

Biological Sciences

Tuna are endothermic fish with high metabolic rates, cardiac outputs and aerobic capacities. While tuna warm their skeletal muscle, viscera, brain and eyes, their hearts remain near ambient temperature, raising the possibility that cardiac performance may limit their thermal niches. We used an in situ perfused heart preparation to investigate the effects of acute temperature change and the effects of epinephrine and extracellular Ca²⁺ on cardiac function in yellowfin tuna (Thunnus albacares). Heart rate showed a strong temperature-dependence, ranging from 20 beats min^-1 at 10 °C to 109 beats min^-1 at 25 °C. Maximal stroke …