Oryzias sarasinorum (POPTA, 1905)

Sarasin's Buntingi

SynonymsTop ↑

Haplochilus sarasinorum Popta, 1905; Xenopoecilus sarasinorum (Popta, 1905) Popta, 1905

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.

sarasinorum: named for Doctors (plural) Sarasin from Basel, Switzerland.

Classification

Order: Beloniformes Family: Adrianichthyidae

Distribution

Endemic to Lake Lindu in Lore Lindu National Park, Sulawesi Tengah (Central Sulawesi) province, Sulawesi, Indonesia.

Habitat

Lore Lindu National Park is a forested reserve encompassing around 2,180 km² and including both lowland and montane forests.

It’s been a designated UNESCO World Biosphere Reserve since 1978 and is home to many rare animals and plants, including over 70 bird species endemic to Sulawesi.

The climate is tropical with high humidity and annual mean temperatures varying between 79-90°F/26.1-??32.2°C in lowland areas, and there is an annual monsoon period between November and April.

In the western section of the park lie a series of valleys which together form the Kulawi Valley. Among these the Palolo, Napu, Lindu and Besoa Valleys were once lakes but are now partially filled with sediment and Lake Lindu (Danau Lindu), located at 960 metres AMSL, is the only large water body remaining.

The lake has experienced considerable environmental degradation, with numerous introduced fishes including Barbonymus, Oreochromis (tilapia), Channa and Clarias spp.

There has also been a degree of runoff from chemical fertilisers used in cultivation of nearby land, and water is extracted from the lake for irrigation.

The conservation status of the native fishes, including O. sarasinorum, is currently unconfirmed but ¡t appears the species has at least become very rare and is under great threat of extinction, meaning aquarium populations should ideally be prioritised for long-term breeding and maintenance.

Its habitat preferences and natural life history are poorly understood, but it’s known to lead a pelagic existence and probably occurs sympatrically with the congener O. bonneorum, another Lake Lindu endemic.

Maximum Standard Length

55 – 60 mm.

Aquarium SizeTop ↑

An aquarium with base dimensions of 100 ∗ 30 cm or more is recommended for a group.

Maintenance

This species has no special requirements in terms of décor though it tends to be more colourful when maintained in a spacious, aquascaped set-up.

Planted aquaria offer fry a more favourable chance of survival alongside the adults, and in small or sparsely-decorated tanks the fish may act nervously and can injure themselves by swimming into the glass (B. Nicca, pers. comm.).

Water Conditions

Temperature: 24 – 29 °C

pH: 7.0 – 8.0

Hardness: 90 – 357 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 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 ↑

Largely non-aggressive, but given its rarity the emphasis should ideally be on captive reproduction and we strongly recommend maintaining it alone.

It fares best when maintained alongside conspecifics and exhibits typical ‘swarming’ behaviour suggesting it naturally occurs in substantially-sized groups, meaning the purchase of six or more specimens should be considered mandatory.

Sexual Dimorphism

Males possess elongate, filamentous rays in the dorsal and anal fins, relatively uniform body shape, and a  genital papilla forming a subconical tube.

In females the pelvic fins are extended, genital papilla consists of a single lobe, and there is a deeply concave area, sometimes referred to as an ‘abdominal cavity’, between the pelvic and anal fins.

Reproduction

Utilises a strategy which has become known as ‘pelvic brooding’.

Spawning tends to occur in the early morning, with dominant males darkening in colouration and defending their space by driving away potential competitors, while approaching ripe females in a rigid ‘head-down’ position.

The eggs normally number 8-12 and are expelled as a single mass while being fertilised simultaneously, after which they continue to hang from the genital pore of the female via adhesive filaments.

Unlike in most Oryzias species however they are not brushed off after a few hours, rather the female carries them in the abdominal cavity using the elongate pelvic fins to keep them in place.

Egg-carrying females do not spawn again until hatching is complete, but often do so within a few days of fry being released.

The incubation period is temperature dependant to an extent but typically 14-20 days.

While the adults tend to ignore the eggs they do predate free-swimming fry, though if the tank is densely-planted with fine-leaved or floating plants such as Cabomba, Ceratophyllum or Taxiphylum spp. some will usually survive.

Alternatively fry can be removed to a separate rearing container filled with water from the adults tank, or the female segregated from the rest of the adult group until hatching.

Once free-swimming the fry are able to accept microworm, Artemia nauplii, etc., immediately.

NotesTop ↑

This species is also known as Sarasin’s minnow and is exceptionally rare both in nature and the aquarium hobby.

It was formerly included in the now defunct genus Xenopoecilus which comprised three species but was found to be paraphyletic and therefore split up by Parenti (2008).

The other two species (now A. oophorus and A. poptae) were moved into the genus Adrianichthys, all four members of which are endemic to Lake Poso in Central Sulawesi.

It can be further distinguished from congeners by the following combination of characters: possession of broad, silvery, lateral stripe extending from behind the head to the caudal peduncle base; high number of lateral scales (70-75 vs. 24-54 in all other Oryzias spp.); 15 (vs. 14 or fewer) precaudal vertebrae; pelvic brooding reproductive strategy; 11-12 dorsal-fin rays; 21-22 anal-fin rays without bony contact organs; 10-11 pectoral-fin rays; palatine and quadrate bones connect anteriorly via elongate flanges.

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. Popta, C. M. L., 1905 - Notes from the Leyden Museum 25(4): 239-247
   Haplochilus sarasinorum, n. sp.
2. 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.
3. 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.
4. 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.
5. 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).
6. 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.
7. 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.
8. 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.
9. Rosen, D. E. and L. R. Parenti. 1981 - American Museum Novitates 2719: 1–25
   Relationships of Oryzias, and the groups of atherinomorph fishes.
10. 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.
11. 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.
12. Uwa, H. and W. Magtoon, 1986 - Copeia 1986 (2): 473-478
    Description and karyotype of a new ricefish, Oryzias mekongensis from Thailand.