Osteoglossum bicirrhosum Vandelli, 1829.
Species overview
Large fish, the straight upper profile of the head continuing without marked border into the straight outline of the back. The underside of the head makes an acute angle with the forehead, chin with two long barbles. Eye large with silvery iris and green sclera. Pectoral and pelvic fins long, pointed; dorsal and anal fin long; caudal fin rather small on a short peduncle. Silvery with a greenish and reddish hue, borders of the quite large scales green; unpaired fins mottled greenish- reddish with white tips. Common name: Silver arawana or aruana.
Size observed: up to 1 m.
Taxonomic description
-Body moderately compressed, oval in cross section, outline of back straight up to about middle of dorsal fin, greatest depth above pelvic fins, underside of body slightly convex, bent towards caudal peduncle.
-Head moderately long, upper profile straight; underside steep, running parallel to buccal cleft, forming an angle of about 45° with forehead.
-Mouth supraterminal, wide, its edge deep below and behind posterior rim of eye.
-Chin with two fleshy barbles which in life are pointing foreward. Eye large, its diameter similar to snout length.
-Opercular cleft long, semicircularly curved.
-Pectoral fin origination at lower curvature of the opercle, long, pointed, extending somewhat behind middle of pelvic fin.
-Pelvic fin abdominal, originating ca. at first third of body, pointed, extending behind origin of anal fin.
-Dorsal fin long, 42-57 fin-rays, originating clearly posterior to middle of body, behind anal.
-Anal fin even longer than dorsal, its origin at about middle of body. Fin-rays of both dorsal and anal fin increasing in length towards the tail, the rays of the anal genrally are longer than the ones of the dorsal fin.
-Caudal peduncle short; caudal fin rather small, rounded, longer than deep.
-Scales large, about ten rows along the body.
-Coloration: Silvery with greenish hue, scales with reddish center and green border; dorsal and anal fin mottled greenish reddish, tips of fin-rays white. Juveniles are much brighter in colours.
Type locality
Not known.
Distribution
Tropical South America, Amazon basin and Guayanas.