Molecular Biology and Genetics
Statistics of barcoding coverage
|Specimen Records:||70||Public Records:||57|
|Specimens with Sequences:||71||Public Species:||3|
|Specimens with Barcodes:||70||Public BINs:||3|
|Species With Barcodes:||4|
Arowanas are freshwater bony fish of the family Osteoglossidae, also known as bonytongues. In this family of fish, the head is bony and the elongate body is covered by large, heavy scales, with a mosaic pattern of canals. The dorsal and the anal fins have soft rays and are long based, while the pectoral and ventral fins are small. The name "bonytongues" is derived from a toothed bone on the floor of the mouth, the "tongue", equipped with teeth that bite against teeth on the roof of the mouth. The arowana is a facultative air breather and can obtain oxygen from air by sucking it into the swim bladder, which is lined with capillaries like lung tissue. 
Osteoglossids are basal (primitive) fish from the lower Tertiary and are placed in the actinopterygiid order Osteoglossiformes. There are ten described living species: three from South America, one from Africa, four from Asia, and the remaining two from Australia.
The Osteoglossidae are the only exclusively freshwater fish family found on both sides of the Wallace Line. This may be explained by the theory that Asian arowanas (S. formosus) diverged from the Australian Scleropages, S. jardinii and S. leichardti, about 140 million years ago, making it likely that Asian arowanas were carried to Asia on the Indian subcontinent.
A genetic study shows that the lineage leading to the arapaima and African arowana diverged about 220 million years ago, during the Late Triassic; the lineage leading to the silver and blackish blue arowanas of South America diverged about 170 million years ago, during the Middle Jurassic. The lineage leading to the Australian arowanas diverged from that leading to the Asian arowanas about 140 million years ago, during the Early Cretaceous.
At least five extinct genera, known only from fossils, are classified as Osteoglossids; these date back at least as far as the Late Cretaceous. Other fossils from as far back as the Late Jurassic or Early Cretaceous are widely considered to belong to the arowana superorder Osteoglossomorpha. Osteoglossomorph fossils have been found on all continents except Antarctica. These fossil genera include Brychaetus, Joffrichthys, and Phareodus.
Osteoglossids are carnivorous, often being specialized surface feeders. They are excellent jumpers; it has been reported that Osteoglossum species have been seen leaping more than 6 feet (almost 2 metres) from the water surface to pick off insects and birds from overhanging branches in South America, hence the nickname "water monkeys". Arowana species typically grow to around 2 to 3 feet in captivity.
Several species of osteoglossid exhibit parental care. They build nests and protect the young after they hatch. All species are mouthbrooders, the parents holding sometimes hundreds of eggs in their mouths. The young may make several tentative trips outside the parent's mouth to investigate the surroundings before leaving permanently.
In the aquarium
Arowanas are solitary fish and only appreciate company while young; adults may show dominance and aggression. Some compatible species often partnered with this fish are clown knifefish, pacu, oscars, plecostomus, jaguar cichlids, green terrors, gar, tinfoil barb, siamese tigerfish, and any other semi-aggressive fish that cannot fit in the arowana's mouth.
These fishes are best kept with live or frozen feed and they easily outgrow the tank within a span of 8 to 10 months. A large type aquarium of at least 150 gallons is preferable.
The name comes from the Indonesian arwana or nirwana, meaning fish of paradise.
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