Organism
Bluefin Tuna
TL;DR
Demonstrates regional heterothermy: swims in 50°F water but maintains red swimming muscle at 86°F, brain/eyes at 77°F, heart at 68°F, gills at 50°F.
Demonstrates regional heterothermy: swims in 50°F water but maintains red swimming muscle at 86°F, brain/eyes at 77°F, heart at 68°F, gills at 50°F. The rete mirabile blood vessel network retains heat in muscles while gills match water temperature for gas exchange. Warm red muscle produces 3× power output, enabling 6 mph cruise speed sustained indefinitely and 5,000-mile migrations without feeding.