albacares, 673â2470g, 33â53cm fork length, FL) was examined in unanesthetized fish swimming in a large water tunnel. Yellowfin tuna were fitted with either.
1975
The Journal of Experimental Biology 200, 1975–1986 (1997) Printed in Great Britain © The Company of Biologists Limited 1997 JEB0747
HEART RATE AND STROKE VOLUME CONTRIBUTIONS TO CARDIAC OUTPUT IN SWIMMING YELLOWFIN TUNA: RESPONSE TO EXERCISE AND TEMPERATURE KEITH E. KORSMEYER1,*, N. CHIN LAI1,2, ROBERT E. SHADWICK1 AND JEFFREY B. GRAHAM1 for Marine Biotechnology and Biomedicine, and Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0204, USA and 2Veterans Administration Medical Center, Research Division – Cardiology 111A, 3350 La Jolla Village Drive, San Diego, CA 92161, USA
1Center
Accepted 1 May 1997 Summary Cardiac performance in the yellowfin tuna (Thunnus Blood flow measurements revealed a mean increase in albacares, 673–2470 g, 33–53 cm fork length, FL) was relative cardiac output of 13.6±3.0 % with exercise (mean examined in unanesthetized fish swimming in a large water velocities 1.23–2.10 FL s−1) caused by an 18.8±5.4 % tunnel. Yellowfin tuna were fitted with either increase in fH and a 3.9±2.3 % decrease in stroke volume. electrocardiogram electrodes or a transcutaneous Doppler These results indicate that, unlike most other fishes, blood-flow probe over the ventral aorta and exposed to cardiac output in yellowfin tuna is regulated primarily changes in swimming velocity (range 0.8–2.9 FL s−1) or to through increases in fH. Acute reductions in ambient an acute change in temperature (18–28 °C). Heart rates (fH) temperature at slow swimming velocities resulted in at 24±1 °C (30–130 beats min−1) were lower on average than decreases in cardiac output (Q10=1.52) and fH (Q10=2.16), previous measurements with non-swimming (restrained) but increases in stroke volume (Q10=0.78). This observation tunas and comparable with those for other active teleosts suggests that the lack of an increase in stroke volume at similar relative swimming velocities. Although highly during exercise is not due to the tuna heart operating at variable among individuals, fH increased with velocity (U, maximal anatomical limits. in FL s−1) in all fish (fH=17.93U+49.93, r2=0.14, P
