single species. In 1999, Collette established that based on both molecular and morphological considerations, they are in fact distinct species. The genus Thunnus is further classified into two subgenera: Thunnus (Thunnus) (the bluefin group), and Thunnus (Neothunnus) (the yellowfin group). |} Other species The Thunnini tribe also includes seven additional species of tuna across four genera. They are: {| class="wikitable" |- ! colspan="9"| Other tuna species |- ! style="width:10em" | Common name ! style="width:11em" | Scientific name ! Maximumlength ! Commonlength ! Maximumweight ! Maximumage ! Trophiclevel ! Source ! style="width:11em" |IUCN status |- | Slender tuna | Allothunnus fallai(Serventy, 1948) | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| | style="text-align:center;"| 3.74 | style="text-align:center;"| | Least concern |- | Bullet tuna | Auxis rochei(Risso, 1810) | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| 5 years | style="text-align:center;"| 4.13 | style="text-align:center;"| | Least concern |- | Frigate tuna | Auxis thazard (Lacépède, 1800) | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| 5 years | style="text-align:center;"| 4.34 | style="text-align:center;"| | Least concern |- | Mackerel tuna,Kawakawa | Euthynnus affinis(Cantor, 1849) | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| 6 years | style="text-align:center;"| 4.50 | style="text-align:center;"| | Least concern |- | Little tunny | Euthynnus alletteratus(Rafinesque, 1810) | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| 10 years | style="text-align:center;"| 4.13 | style="text-align:center;"| | Least concern |- | Black skipjack tuna | Euthynnus lineatus(Kishinouye, 1920) | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| | style="text-align:center;"| 3.83 | style="text-align:center;"| | Least concern |- | Skipjack tuna | Katsuwonus pelamis(Linnaeus, 1758) | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| | style="text-align:right;"| 6–12 yrs | style="text-align:center;"| 3.75 | style="text-align:center;"| | Least concern |} Biology Description The tuna is a sleek and streamlined fish, adapted for speed. It has two closely spaced but separated dorsal fins on its back; The first fin is "depressible" – it can be laid down, flush, in a groove that runs along its back; it is supported by spines. Seven to 10 yellow finlets run from the dorsal fins to the tail, which is lunate – curved like a crescent moon – and tapered to pointy tips. A tuna's pelvic fins are located below the base of the pectoral fins. Both dorsal and pelvic fins retract when the fish is swimming fast. The tuna's body is countershaded to camouflage itself in deeper water when seen from above, its dorsal side is generally a metallic dark