Arowana

This article is about fishes. For the genus of jumping spiders, see Aruana (spider).

Arowana
Silver arowana, Osteoglossum bicirrhosum
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Osteoglossiformes
Family:	Osteoglossidae Bonaparte, 1832
Genera
Subfamily Heterotidinae  Arapaima  Heterotis Subfamily Osteoglossinae  Osteoglossum  †Phareodus  Scleropages

Arowanas are freshwater bony fish of the family Osteoglossidae, also known as bonytongues.^[1] In this family of fishes, 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 fish can obtain oxygen from air by sucking it into the swim bladder, which is lined with capillaries like lung tissue. The arowana is an "obligatory air breather".^[2]

Classification and distribution

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.^[1]

Osteoglossidae is the only exclusively freshwater fish family found on both sides of the Wallace Line.^[3] This may be explained by the fact 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.^[4][5]

Behavior

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 extensive 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.These fishes are best kept with live or frozen feed and they easily outgrow the tank within a span of 8-10 months. Always preferred in a large type aquarium of at least 150 gallons.^[6]

In the aquarium

Arowanas are solitary fish and only appreciate company while young; adults may show excessive dominance and aggression. Some compatible fish often partnered with this fish are clown knifefish, pacu, oscars, plecostomus, jaguar cichlids, green terrors, gar, siamese tigerfish (datnioides microlepis) and any other semi-aggressive fish that cannot fit in the arowana's mouth.

Australian species are best kept singular in aquaria.^[7][8]

Species

The family contains two subfamilies, Heterotidinae and Osteoglossinae, with all but two of the ten extant species being members of the latter. Species are given with one or more prominent common names.

Family Osteoglossidae

• Subfamily Heterotidinae
  • Genus Arapaima
    • Arapaima or pirarucu, Arapaima gigas (Cuvier, 1829)
  • Genus Heterotis
    • African arowana, Heterotis niloticus (Cuvier, 1829)
• Subfamily Osteoglossinae
  • Genus Osteoglossum (Cuvier, 1829)
    • Silver arowana, Osteoglossum bicirrhosum (Cuvier, 1829)
    • Black arowana, Osteoglossum ferreirai Kanazawa, 1966
  • Genus Scleropages
    • Red-tailed golden arowana Scleropages aureus (Pouyad, Sudarto & Teugels, 2003)
    • Green arowana or gold crossback arowana, Scleropages formosus (Schlegel & Müller, 1844)
    • Gulf saratoga, red saratoga or northern spotted barramundi, Scleropages jardinii ^‡ (Saville-Kent, 1892)
    • Red arowana, super red arowana, or chili red arowana, Scleropages legendrei (Pouyad, Sudarto & Teugels, 2003)
    • Saratoga, silver saratoga or spotted barramundi, Scleropages leichardti ^‡ Günther, 1864
    • Silver Asian arowana, Scleropages macrocephalus (Pouyad, Sudarto & Teugels, 2003)

^‡This species is one of two sometimes called the Australian arowana or Australian bonytongue.

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.^[5]

Fossil record

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.^[9] These fossil genera include Brychaetus, Joffrichthys, and Phareodus.

References

1. ^ ^{a b} Allen, G. R.; Midgley, S. H.; Allen, M. (2002). Field Guide to the Freshwater Fishes of Australia. Perth: Western Australia Museum. pp. 56–58. ISBN 0-7307-5486-3. 
2. ^ Berra, Tim M. (2001). Freshwater Fish Distribution. San Diego: Academic Press. ISBN 0-12-093156-7. 
3. ^ Ismail, Mohd Zakaria (1989) (doctoral dissertation). Systematics, Zoogeography, and Conservation of the Freshwater Fishes of Peninsular Malaysia. Colorado State University. pp. 25. 
4. ^ Kumazawa, Yoshinori; Nishida, Mutsumi (1 December 2000). "Molecular Phylogeny of Osteoglossoids: A New Model for Gondwanian Origin and Plate Tectonic Transportation of the Asian Arowana". Molecular Biology and Evolution 17 (12): 1869–78. PMID 11110903. http://mbe.oxfordjournals.org/cgi/content/abstract/17/12/1869. Retrieved 2006-07-12. 
5. ^ ^{a b} Kumazawa, Yoshinori (2003). "The reason the freshwater fish arowana live across the sea". Quarterly Journal Biohistory (Winter). http://www.brh.co.jp/en/experience/journal/39/research_1.html. Retrieved 2006-07-02. 
6. ^ Greenwood, P.H. & Wilson, M.V. (1998). Paxton, J.R. & Eschmeyer, W.N.. ed. Encyclopedia of Fishes. San Diego: Academic Press. pp. 81–82. ISBN 0-12-547665-5. 
7. ^ Native Fish Australia, Saratoga - http://www.nativefish.asn.au/saratoga.html
8. ^ Native Fish Australia, Gulf Saratoga - http://www.nativefish.asn.au/gulf_saratoga.html
9. ^ Guo-Qing, Li; Wilson, Mark V. H. (1998). "Osteoglossomorpha" (article). Tree of Life. http://tolweb.org/tree?group=Osteoglossomorpha&contgroup=Teleostei. Retrieved 2006-04-14. 

• Lim, Eugene (2006). "Arowana / Arawana". Aquarium Lore. http://aquariumlore.blogspot.com/2006/04/arowana.html. Retrieved April 20, 2006. 

External links

• Fishbase article
• Arowana Malaysia