Tuna

Tuna
Tunas (from top): albacore, Atlantic bluefin, skipjack, yellowfin, bigeye
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Scombriformes
Family:	Scombridae
Subfamily:	Scombrinae
Tribe:	Thunnini Starks, 1910
Genera
Allothunnus: slender tunas Auxis: frigate tunas Euthynnus: little tunas Katsuwonus: cocinal tunas Thunnus: albacores, true tunas

Tuna, sometimes called tuna fish, are several species (kinds) of fish. They are in the family Scombridae, mostly in the genus Thunnus.

Tuna are fast swimmers. People have seen tuna swim at up to 77 km/h. Several species of tuna are warm-blooded. Most species of fish have white flesh. The flesh of the tuna is different. It is pink to dark red. This is because tuna muscle tissue contains greater quantities of myoglobin. Myoglobin is a molecule that binds oxygen. Some of the larger tuna species such as the Northern bluefin tuna can raise their blood temperature above the water temperature with muscular activity. This enables them to live in cooler waters and survive a wider range of circumstances.