Fig. 3. Comparison of cardiac performance in situ in three tuna species. Maximal values of cardiac parameters recorded in spontaneously beating hearts of albacore tuna (red triangles), bluefin tuna (blue squares) and yellowfin tuna (yellow diamonds) are presented. (A) Heart rate, (B) stroke volume, (C) cardiac output, (D) power output. Sample sizes for bluefin tuna are as in Fig. 3. Values are means ± S.E.M.; for yellowfin tuna, N=4 (10°, 25°), N=5 (15°, 20°); for albacore tuna, N=1.