Description
Asian arowanas grow up to 90 cm (35 in) total length. Like all Scleropages, Asian arowanas have long bodies; large, elongate pectoral fins; dorsal and anal fins located far back on the body; and a much larger caudal fin than that of their South American relative, the silver arowana, Osteoglossum bicirrhosum. The mouth is oblique with a very wide gape. The prominent lower jaw has two barbels at its tip. The gill rakers are stout. Asian arowanas bear teeth on many bones of the mouth, including the jaws, vomer, palatines, pterygoids, parasphenoid, and tongue.
Asian arowana scales are large, cycloid, and, in some varieties, metallic coloured, with a distinctive mosaic pattern of raised ribs. The lateral scales are arranged in horizontal rows numbered from the most ventral (first level) to the most dorsal (fifth level), with dorsal scales designated the sixth level.
Asian arowanas are distinguished from Australian congenerics S. jardinii and S. leichardti by having fewer (21-26) lateral line scales (versus 32-36 for the Australian species), longer pectoral and pelvic fins, and a longer anterior snout.
Green arowanas are dark green on the back, silvery or golden green on its sides, and silvery or whitish on its ventral surface, with dark greenish or bluish patches visible through the lateral scales. In mature fish, the top of the eye and the head behind the eye are bright emerald.
Both grey-tailed and yellow-tailed silver Asian arowanas are dark grey on the back and silver on the sides, with dark ring patches on the lateral scales and a silvery or whitish belly. In yellow-tailed specimens, the fin membranes are yellowish with dark grey rays. In grey-tailed specimens, the fins are uniform dark grey.
Mature red-tailed golden arowanas have brilliant metallic gold lateral scales, gill covers, bellies, and pectoral and pelvic fin membranes, although the back is dark. In juveniles the areas destined to develop golden colour start out metallic silver. The anal fin and the bottom portion of the caudal fin are light brown to dark red.
Mature gold crossback arowanas are distinguished from the red-tailed golden arowanas by having metallic gold crossing the back completely. This variety also lacks the reddish fins of the red-tailed golden.
In mature super red arowanas, the gill covers, lateral scales, and fin membranes of these fishes are metallic red, with the exact hue varying from gold-tinged to deep red. The back is dark brown. In juveniles, the darker the dorsal colouration, the deeper the red will be on maturity.
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