Oryzias celebensis (WEBER, 1894)

Celebes Ricefish

SynonymsTop ↑

Haplochilus celebensis Weber, 1894

Etymology

Oryzias: from the Greek ὄρυζα (oryza), meaning ‘rice’, in reference to the tendency of some members of the genus to inhabit rice paddy fields.

celebensis: ‘from Celebes’, Celebes being the former name of Sulawesi, Indonesia.

Classification

Order: Beloniformes Family: Adrianichthyidae

Distribution

Described from the Maros River (Salo Maros), southwestern Sulawesi, Indonesia and subsequently recorded from rivers and streams throughout the southwestern arm of the island including Lake Tempe (Danau Tempe), plus the Mota Talau River, East Timor state on the nearby island of Timor.

Type locality is given as ‘Makassar, Maros River near Maros, Sulawesi, Indonesia’.

More recently Herder and Chapuis (2010) reported it to be more widespread on Sulawesi, with new records pertaining to an unnamed small stream within the upper Cerekang River system, close to Lake Matano in the central part of the island (though within the boundaries of South Sulawesi province).

The authors also note that the Cerekang shares its estuary with the Larona River which is the outflow of the Malili Lakes system, and speculate that O. celebensis may have a wider distribution in the area.

Habitat

The Maros area is mostly karstic meaning the rivers and streams there tend to flow over limestone, though not all habitats feature such conditions.

O. celebensis is mostly found in slow-moving or standing waters, often in areas where aquatic plants proliferate.

In Lake Tempe, for example, resident plant species include Ceratophyllum demersum, Pistia stratiotes, lpomoea aquatica, Polygonum sp., Cyperus platystylis and Echinochloa crusgelii.

Maximum Standard Length

25 – 45 mm.

Aquarium SizeTop ↑

An aquarium with base dimensions of 45 ∗ 30 cm or more is recommended for a group.

Maintenance

Best maintained in a heavily planted set-up, ideally with a dark substrate, patches of dense vegetation, and some open areas.

Other décor can consist of twisted roots and pieces of bogwood, while surface vegetation is also appreciated by the fish.

When maintained under such conditions they’re more likely to display their best colours, and planted aquaria also offer fry a more favourable chance of survival alongside the adults.

Water Conditions

Temperature: 23 – 27 °C

pH: 7.0 – 9.0; will probably fail to thrive if maintained long term in acidic water.

Hardness: 90 – 447 ppm

Diet

Probably a micropredator feeding on small insects, worms, crustaceans and other zooplankton in nature.

In the aquarium it will accept dried foods of a suitable size but should also be offered daily meals of small live and frozen fare such as Daphnia, Artemia, chopped bloodworm, etc., along with good quality, suitably-sized flakes and granules.

Behaviour and CompatibilityTop ↑

Generally peaceful but doesn’t make an ideal addition to many communities due to its small size.

Should you wish to maintain it alongside other fishes diminutive species enjoying similar conditions such as Microdevario, Trigonostigma, Pseudomugi and some Danio spp. constitute the best options, while freshwater shrimp of the genera Caridina and Neocaridina are also suitable as are most snails.

If the intention is breeding then obviously it should ideally be maintained alone, and we don’t recommend keeping it with other Oryzias spp. due to the potential of hybridisation, already proven in laboratory experiments.

It is mostly non-aggressive towards congeners although rival courting males can be aggressive towards one another, and tends to look most effective and behave more confidently in a group of 8 or more.

Sexual Dimorphism

Adult males are considerably more colourful, possess longer dorsal and anal fins, and have a slimmer body shape than females.

In males the distal margin of the anal-fin is convex and the genital papilla forms a short tube, while in females the anal-fin margin is slightly concave and the genital papilla bilobed.

Reproduction

Quite easy to breed and fairly prolific, with females capable of producing batches of eggs every few days or even on a daily basis when in good condition.

Spawning normally occurs in the early morning, with males darkening in colouration and defending small, temporary territories against one another while attempting to entice females.

The adhesive eggs are typically expelled as a single mass and fertilised simultaneously, after which they continue to hang from the genital pore of the female for a period before eventually being deposited singly or in small clumps among vegetation or other suitable media.

Fine-leaved plants such as Cabomba, Ceratophyllum or Taxiphylum spp. are ideal, but synthetic spawning mops or other artificial alternatives also work.

The incubation period is temperature dependant to an extent but typically 1-3 weeks, and while the adults tend to ignore the eggs they do predate free-swimming fry, though if the tank is densely-planted some will usually survive.

Alternatively the eggs or fry can be removed to a separate rearing container filled with water from the adults tank. Once free-swimming the fry are able to accept microworm, Artemia nauplii, etc.

Caution is recommended when housing juveniles of different ages together as the older will predate on the younger if there is a large enough discrepancy in size.

NotesTop ↑

This species is infrequently available in the aquarium hobby but is exported on occasion and sometimes referred to as ‘Celebes medaka’.

It has a truncate, rather than lunate or emarginate, caudal-fin which distinguishes it from the congeners O. bonneorum, O. nebulosus, O. nigrimas, O. orthognathus, and O. sarasinorum, and in this respect appears to be a member of a large, unnamed clade or species group containing all other members of the genus.

It’s further distinguishable from congeners by the following combination of characters: pelvic fins relatively small, usually with 6 rays and not extending past the anterior margin of the genital area; 8-10 dorsal–fin rays (usually 8); 20-23 anal-fin rays (usually 22) and in males without bony contact organs; possession of yellow to orange submarginal bands on the caudal-fin lobes; dark brown to black vertically-orientated markings on lower part of flanks.

Members of the family Adrianichthyidae are often referred to collectively as ‘ricefishes’ and were traditionally considered to be members of the family Cyprinodontiformes and thus closely-related to toothcarps.

This misconception is sometimes still upheld despite the fact that Rosen and Parenti reclassified them within the cyprinodontiform sister group Beloniformes as long ago as 1981.

The best-known member of the family is the medaka or Japanese ricefish, Oryzias latipes, which has been widely used as a model organism in genomic and experimental biology for well over a century and was the first vertebrate animal to mate in space during the mid-1990s.

There are currently just two genera included in the family, Oryzias and Adrianichthys, with the historically-recognised groupings Xenopoecilus and Horaichthys having been synonymised with Oryzias by Parenti (2008).

Of the three species previously included in the paraphyletic Xenopoecilius, X. oophorus and X. poptae were moved into Adrianichthys with the third, X. sarasinorum currently recognised as Oryzias sarasinorum.

In addition the formerly monotypic Indian species Horaichthys setnai is currently classified as O. setnai.

References

1. Herder, F. and S. Chapuis, 2010 - The Raffles Bulletin of Zoology 58(2): 269-280
   Oryzias hadiatyae, a new species of ricefish (Atherinomorpha: Belonifornes: Adrianichthyidae) endemic to Lake Masapi, Central Sulawesi, Indonesia.
2. Magtoon, W., 2010 - Tropical Natural History 10(1): 107-129
   Oryzias songkhramensis, a new species of ricefish (Beloniformes; Adrianichthyidae) from northeast Thailand and central Laos.
3. Magtoon, W. and A. Termvidchakorn, 2009 - The Natural History Journal of Chulalongkorn University 9(1): 35-68
   A Revised Taxonomic Account of Ricefish Oryzias (Beloniformes; Adrianichthyidae), in Thailand, Indonesia and Japan.
4. Parenti, L. R., 2008 - Zoological Journal of the Linnean Society 154(3): 494-610
   A phylogenetic analysis and taxonomic revision of ricefishes, Oryzias and relatives (Beloniformes, Adrianichthyidae).
5. Parenti, L. R. and B. Soeroto, 2004 - Ichthyological Research 51(1): 10-19
   Adrianichthys roseni and Oryzias nebulosus, two new ricefishes (Atherinomorpha: Beloniformes: Adrianichthyidae) from Lake Poso, Sulawesi, Indonesia.
6. Parenti, L. R. and R. K. Hadiaty, 2010 - Copeia 2010 (2): 268-273
   A new, remarkably colorful, small ricefish of the genus Oryzias (Beloniformes, Adrianichthyidae) from Sulawesi, Indonesia.
7. Roberts, T. R., 1998 - Ichthyological Research 45(3): 213-224
   Systematic observations on tropical Asian medakas or ricefishes of the genus Oryzias, with descriptions of four new species.
8. Rosen, D. E. and L. R. Parenti, 1981 - American Museum Novitates 2719: 1–25
   Relationships of Oryzias, and the groups of atherinomorph fishes.
9. Takehana, Y., K. Naruse K and M. Sakaizumi, 2005 - Molecular Phylogenetics and Evolution 36(2): 417–428
   Molecular phylogeny of the medaka fishes genus Oryzias (Beloniformes: Adrianichthyidae) based on nuclear and mitochondrial DNA sequences.
10. Uwa, H. and L. Parenti, 1988 - Japanese Journal of Ichthyology 35(2): 159-166
    Morphometric and meristic variation in ricefishes, genus Oryzias: a comparison with cytogenetic data.