On this Wikipedia the language links are at the top of the page across from the article title. For other uses, tuna salad with egg Las Tunas.

Tuna, opah and mackerel sharks are the only species of fish that can maintain a body temperature higher than that of the surrounding water. Found in warm seas, the tuna is commercially fished extensively as a food fish, and is popular as a bluewater game fish. The cladogram is a tool for visualizing and comparing the evolutionary relationships between taxa, and is read left-to-right as if on a timeline. The following cladogram illustrates the relationship between the tunas and other tribes of the family Scombridae.

The “true” tunas are those that belong to the genus Thunnus. Until recently, it was thought that there were seven Thunnus species, and that Atlantic bluefin tuna and Pacific bluefin tuna were subspecies of a single species. The Thunnini tribe also includes seven additional species of tuna across four genera. Bigeye tuna Thunnus obesus showing finlets and keels.

The tuna is a sleek and streamlined fish, adapted for speed. The tuna’s body is countershaded to camouflage itself in deeper water when seen from above, its dorsal side is generally a metallic dark blue while the ventral or under side is silvery or whitish. Tunas achieve endothermy by conserving the heat generated through normal metabolism. In all tunas, the heart operates at ambient temperature, as it receives cooled blood, and coronary circulation is directly from the gills. Also unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red.