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Osteoglossidae

GENERAL INFORMATION

• Fish belonging to the Family Osteoglossidae (oss-tea-oh-gloss-ID-ee) are an ancient group of freshwater fish that evolved entirely in freshwater, rather than from invading marine ancestors. Fossil records show their presence in Australia and other continents during the Eocene period between 38 and 55 million years ago - but it is likely that the group is much older.
• The name Osteoglossidae is derived from the Latin word osseus meaning bony and the Greek word glossa meaning tongue. The common name Bony Tongue is derived from the toothed bone on the floor of the mouth - this tongue is equipped with teeth that bite against teeth on the roof of the mouth.
• Four genera and seven species exist today, spread across Asia, South America, Africa and Australia - continents that once formed the Gondwanan supercontinent before it drifted apart some 135 million years ago.
• The family includes the South American giant, Arapima gigas, the second largest freshwater fish in the world, which grows over 3 metres in length (right).
• There are two sub-families:
  • Heterotidinae (Arapima gigas from South America and the metre long Heterotis niloticus - sometimes sold as "African Arowana" - from west Africa) and
  • Osteoglossinae.
• The Arapima gigas is endangered in the wild and is listed on the CITES Red List. Neither representative of the sub-family Heterotidinae is found in Queensland.
• The sub-family Osteoglossinae is made up of two genera and five species:
  • Osteoglossum (Arowana) from South America - Osteoglossum bicirrhosum (Silver Arowana) and Osteoglossum ferrarai (Black Arowana)
  • Scleropages from Australia (Saratoga - Scleropages jardinii and Scleropages leichardtii) and Asia (Asian Arowana - Scleropages formosa).
• The species of this sub-family have been used to support the continental drift theory since members from different areas closely resemble one another.
• It is believed that representatives also once existed in North America, Europe, and India, but died off for some reason.
• The fish of this sub-family are of most importance to the Queensland aquarium and fisheries industries.

Distinguishing characteristics....

• Osteoglossidae are distinguished by:
  • An elongated laterally compressed body that is covere in large bony scales
  • Bony plates protecting the head
  • Large eyes
  • Large trap-like upward-facing mouth and
  • A single dorsal fin directly opposite the anal fin.
• The sub-family Osteoglossinae are further distinguished by having a pair of sensory barbels on the lower jaw (right), which are missing in the sub-family Heterotidinae.

Habitat and environment....

• All Osteoglossidae like dark, heavily vegetated areas with penty of swimming space.
• Suitable floating plants, like Riccia or the Indian Water Fern Ceratopteris provide good cover.
• Rooted varieties need to be tough and securely positioned to put up with the thrashing movements during food searching and seizure.

Care and maintenance....

• All Osteoglossidae need very large tanks.
• All members will jump so tanks wth lids are a must.
• Lighting should be subdued and the tank located out of main traffic where the least amount of walk-by or tank-bumping occurs.
• Water parameters:
  • These fish prefer a pH of around 6.5-7.5, temperature in the mid to high 20s and medium hardness.
  • The emphasis with these fish should be on stability, keeping your water near consistent through filtration and water changing, not intentionally fooling with any given set of values.
• Disease:
  • As juveniles many of these fish are susceptible to white-spot disease (ichthyophthiriasis) and bacterial secondary infections due to physical trauma.

Feeding....

• Osteoglossidaes are carnivorous, although they can be trained to eat non-moving prey such as frozen pilchards, floating pellets and other frozen food. Earthworms and crickets will also be eaten.
• Juveniles may be trained to take flake and they will relish live black worms and small earthworms.
• In the wild, Arowana are known to eat little river bats and birds that they take from the air by leaping out of the water.
• Arowana have an extremely flexible body and this enables them to coil to get the thrust needed to leap out of the water (picture right shows the ability to turn in tight circles due to the flexibility of the spine). They can leap up to 2 metres out of the water!
• While Saratoga and Asian Arowanas are not quite as flexible, they are still powerful jumpers.
• Take care to avoid spiney foods and the ingestion of other livestock that can choke or puncture the gut of the Osteoglossidae.
• After jumping out, choking is probably the second most common cause of death.

Compatibility....

• Many of these fish are antisocial as adults, becoming very aggressive towards their own kind as well as similar looking fish.
• Though they can be individual differences, most specimens tolerate other fish that are too large to swallow - all will attempt and probably succeed in eating other fish if they are slow or small enough, even armoured catfish.
• Tankmates need to be chosen with care, as apart from eating the entire community, they may also choke on some fish such as the armoured catfish.
• Large fish such as Prochilidus, Clown Knifefish, Clown Loach, Giant Gourami; Lungfish, Eeltail Catfish, Sleepy Cod; Archerfish; Tinfoil Barbs and adult Sailfin Plecos are all suitable tankmates for Saratoga and Arowana.
• Photo (right) shows an Arowana with a Giant Red-finned Gouami and a Red Hook. In the same tank are Prochilodus and an Oscar.

Breeding....

• These fish are mouthbrooders and exhibit extensive parental care.
• In Arowana the male incubates the eggs in his throat pouch (right); in Saratoga the females incubates the eggs.
• Young are held for about one to two weeks and are then guarded for about four weeks after they are released from the mouth.
• When there is a threat the young retreat to the safety of their parents mouth.

Species of Osteoglossidae available

Osteoglossum bicirrhosum (Silver Arowana)
Scleropages jardini (Gulf Saratoga)
Scleropages leichardti (Southern Saratoga)