Tuna

Tunas are fast swimmers, having been recorded at speeds of 45 miles (72 km) per hour. Unlike most species of fish, tuna have pink to dark red flesh, which comes from the muscle tissue’s higher quantities of myoglobin (an oxygen-binding molecule). Some species of tuna can even raise their blood temperature above the water’s temperature, which helps them live in cooler waters, thereby surviving in a wide range of environments.

The eight species in the Thunnus genus are discussed next.