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Ricefish · Sulawesi ricefish · Oryzias

Oryzias orthognathus

Kottelat, 1990

Sharpjawed buntingi

2 cited sourcesName checked against Eschmeyer’s Catalog of Fishes, update of

IUCNNEAR THREATENED
CARESNOT LISTED
Type localityLake Poso, eastern shore between Tentena and Peura, Sulawesi, Indonesiaper Catalog of Fishes
Scientific size2.5 in6.5 cm total length
Temperature72–77 °F22–25 °C
pH7.5–8.5alkaline
Depth—not recorded
DietNot documented for this species; ricefishes in general take small invertebrates and algae at or near the surface
BreedingNot documented for this species
Sexual dimorphismNot documentedNot documented for this species
PhotographsSee photosGoogle Images →

Oryzias orthognathus is a ricefish from Lake Poso, described by Kottelat in 1990. Its name refers to a straight jaw, in contrast to the upturned jaws of many relatives. FishBase gives a maximum of 2.5 in TL, and the IUCN lists it as Near Threatened.

Taxonomy & naming

Kottelat described the species in 1990 from the eastern shore of Lake Poso between Tentena and Peura. The name comes from Greek roots meaning straight jaw.

Morphology

A ricefish with a more horizontal jaw than other Oryzias, as the name indicates. FishBase gives a maximum of 2.5 in TL, large for the genus.

Habitat

Lake Poso, Central Sulawesi; not known elsewhere. FishBase gives a pH range of 7.5 to 8.5 and a temperature range of 22 to 25 C.

Feeding

Diet is not documented.

Mating

Courtship has not been described.

Breeding

Breeding has not been documented.

In the aquarium

Not kept in the hobby. FishBase describes it as very difficult to maintain in aquaria.

Conservation

The IUCN Red List classes Oryzias orthognathus as Near Threatened, meaning it is close to qualifying for a threatened category.

Common questions

Sharpjawed buntingi (Oryzias orthognathus): how big does it get?
Up to 2.5 in total length (TL).
Sharpjawed buntingi (Oryzias orthognathus): what water temperature does it need?
The atlas records 72–77 °F for this species.
Sharpjawed buntingi (Oryzias orthognathus): what water chemistry suits it?
pH 7.5–8.5.
Sharpjawed buntingi (Oryzias orthognathus): where does it come from?
It is recorded from Indonesia.

Biotope tank mates

Atlas fish recorded from the same waters, whose recorded temperature and pH ranges overlap this one’s and whose adults are within twice its size. A shortlist to research, not a stocking plan: temperament, territory and diet are not checked. Other genera only; this genus is compared below.

Related species compared · Oryzias

SpeciesAdult sizeTemperaturepHHardnessIUCN
Sharpjawed buntingiOryzias orthognathusthis species2.5 in TL72–77 °FpH 7.5–8.5—NT
Black buntingiOryzias nigrimas2 in SL72–77 °FpH 7.5–8.5—NT
Oryzias nebulosus1.5 in SL———NT
Towuti ricefishOryzias profundicola2.5 in TL72–77 °FpH 7.5–8.5—NT
Matano medakaOryzias matanensis2 in TL72–77 °FpH 7.5–8.5—NT
Oryzias kalimpaaensis2 in SL———NE
Oryzias polylepis2 in SL———NE
Oryzias sarasinorum3 in TL75–84 °FpH 7.5–8.5—CR
Celebes medakaOryzias celebensis2 in TL72–86 °FpH 8–9—LC
Javanese ricefishOryzias javanicus2 in TL72–77 °FpH 7.5–8.5—LC
Marmorated medakaOryzias marmoratus1.5 in SL72–77 °FpH 7.5–8.5—NT
Hainan medakaOryzias curvinotus1.5 in TL———DD

Recorded ranges from each species’ own page; hardness is the tolerance its sources give, not a measurement of the water it lives in. See all 40 Oryzias species →

Also from Lake Poso

Sources

  1. FishBase — Oryzias orthognathus Kottelat, 1990
  2. Eschmeyer's Catalog of Fishes (California Academy of Sciences) — Oryzias orthognathus
  3. Kottelat, M. (1990) Synopsis of the endangered buntingi (Osteichthyes: Adrianichthyidae and Oryziidae) of Lake Poso, Central Sulawesi, Indonesia, with a new reproductive guild and descriptions of three new species. Ichthyological Exploration of Freshwaters 1: 49-67
  4. Parenti, L.R. (2008) A phylogenetic analysis and taxonomic revision of ricefishes, Oryzias and relatives (Beloniformes, Adrianichthyidae). Zoological Journal of the Linnean Society 154: 494-610

Naming authority: Oryzias orthognathus in Eschmeyer’s Catalog of Fishes ↗

Last reviewed 2026-10-05.

How to cite

Aquarist Atlas (2026). Oryzias orthognathus. Aquarist Atlas.https://www.aquaristatlas.com/ricefish/oryzias-orthognathus/

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Where it has been recorded

5 georeferenced records (GBIF). Each point is a field observation or museum specimen — pan and zoom to explore where this species turns up. The coordinates come straight from GBIF and are often rounded or tied to the nearest town or river landing, so a dot can sit just beside the actual water rather than in it.

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