THERMOREGULATION OF THE INTRAABDOMINAL TESTES OF THE BOTTLE-NOSED-DOLPHIN (TURSIOPS-TRUNCATUS) DURING EXERCISE

Dolphins possess a vascular countercurrent heat exchanger (CCHE) that functions to cool their intraabdominal testes, Spermatic arteries in t he posterior abdomen are juxtaposed to veins returning cooled blood fr om the surfaces of the dorsal fin and tail flukes, In this study, we i nvestigated the effect of exercise on CCHE function in the bottlenose dolphin, The CCHE hanks a region of the bowel in the posterior abdomen and influences colonic temperatures. A rectal probe housing a linear array of seven copper-constantan thermocouples was designed to measure colonic temperatures simultaneously at positions anterior to, within and posterior to the region of the colon flanked by the CCHE, Immediat ely after vigorous swimming, temperatures at the CCHE decreased relati ve to resting and pre-swim values: post-swim temperatures at the CCHE were maximally 0.5 degrees C cooler than pre-swim temperatures. These data suggest that the CCHE has an increased ability to cool the arteri al blood supply to the testes when the dolphin is swimming, This abili ty could offset the increased thermal load on the testes in an exercis ing dolphin, To the best of our knowledge, this is the first report of deep body cooling in an exercising mammal that is not undertaking a d ive,