AppearanceAsian arowanas grow up to 90 cm total length. Like all "Scleropages", Asian arowanas have long bodies; large, elongated 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 to the most dorsal, with dorsal scales designated the sixth level.
Asian arowanas are distinguished from Australian congenerics "Scleropages jardinii" and "Scleropages leichardti" by having fewer lateral line scales, 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 the 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 uniformly 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.
Naming While most consider the different varieties to belong to a single species, work by Pouyaud et al. (2003) differentiates these varieties into multiple species. They have several other common names, including Asian bonytongue, dragonfish, and a number of names specific to the different color varieties.
BehaviorThey spend the day in the protection of "Pandanus" roots or other structures, and feed at night.
It is normally seen alone or in small groups.
ReproductionUnlike most fish, the Asian arowana reaches sexual maturity relatively late, after 3–4 yr. The females produce few eggs, 30-100, which are quite large. After the eggs are fertilized, the Asian arowana exhibits great parental care with paternal mouthbrooding. Both the fertilized eggs and larvae are brooded within the male's mouth.
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