Taxonomy & naming
Telmatherina celebensis was described by the British-Belgian ichthyologist George Albert Boulenger in 1897, and it is the type species of the genus Telmatherina. It belongs to the family Telmatherinidae, the sailfin silversides, within the order Atheriniformes (the silversides). Eschmeyer's Catalog of Fishes records the valid name as Telmatherina celebensis Boulenger, 1897 (CoF species id 14010, genus id 4763); because the species remains in its original genus, no parenthetical authority is used.
The genus name joins the Greek telma (genitive telmatos), swamp or marsh, with atherina, the classical name for the silverside or smelt — a small swamp-dwelling silverside. The specific epithet celebensis points to Celebes, the historical name for the Indonesian island of Sulawesi, where the species occurs. Aarn, Ivantsoff and Kottelat (1998) revised the family Telmatherinidae, re-diagnosing several taxa and describing the related genus Marosatherina; that work also placed the popular aquarium "Celebes rainbowfish" in Marosatherina ladigesi, not in T. celebensis. The two share a common name in some references but are distinct species. The confusion matters here because almost all hobby care information circulating under "Celebes rainbowfish" applies to M. ladigesi.
Morphology
Telmatherina celebensis is a small, slender, fusiform fish reaching a maximum recorded length of about 2.5 in (standard length, for a male or unsexed specimen). Like other sailfin silversides it carries the family's two dorsal fins and an elongate anal fin, the body laterally compressed and silvery, with the translucent look typical of atheriniform fishes.
Meristic characters from the re-diagnosis fill in the structure. A first dorsal fin precedes a second dorsal with 8 to 11 soft rays; the anal fin carries 12 to 16 soft rays, 12 to 15 of them branched; and the second dorsal and anal fins are rounded at the rear. There are 11 to 14 predorsal scales and 31 to 34 scales in the longitudinal row. Overlapping counts like these, not dramatic colour or shape, are what separate T. celebensis from its congeners in the Malili flock. Detailed live-colour and dimorphism data for this particular species are sparse in the literature.
Habitat
Telmatherina celebensis is endemic to the Malili Lakes system of South Sulawesi, Indonesia — a set of ancient tectonic lakes that have hosted their own in-situ radiation of sailfin silversides, shrimps, and snails. FishBase records the species from Lakes Towuti and Mahalona, and possibly Wawontoa; the IUCN assessment lists Lakes Towuti, Mahalona and Lontoa, together with the River Tominanga, which connects parts of the system.
The fish is freshwater, pelagic, and non-migratory, living in warm tropical waters (recorded around 2 to 3 degrees south latitude) across the open and vegetated zones of these lakes. The Malili Lakes are clear, deep, and chemically distinctive, and the silverside flock in them is a textbook case of lacustrine speciation. That single interconnected basin is also the species' chief vulnerability — there is no outlying population to fall back on. Specific in-situ temperature and pH figures for T. celebensis were not available in the cached sources, so precise water parameters are left undocumented here rather than guessed.
Feeding
Telmatherina celebensis sits low in the food web, with a modeled trophic level of about 3.1 — consistent with a small carnivore or omnivore that takes invertebrate prey. As a pelagic sailfin silverside it would feed in the water column on small aquatic invertebrates, zooplankton, and insect larvae, plus whatever drifting or surface food the open water of the Malili Lakes turns up.
No dietary study specific to this species turned up in the cached sources, so the account stays conservative. The trophic-level figure is modeled, not measured from gut contents, and no captive feeding regime is documented for T. celebensis, since it is rarely kept. Care information circulating under the "Celebes rainbowfish" name applies to the unrelated Marosatherina ladigesi and should not be carried over to this species.
Mating
Reproductive behaviour specific to Telmatherina celebensis is thin in the cached sources, and this account avoids importing details from related species. The sailfin silversides of the Malili Lakes are well known to evolutionary biologists for their courtship and mate choice: several Telmatherina species in the flock show assortative mating and male colour or fin signalling, and those traits have figured large in studies of how the flock diversified.
Whether and how strongly the same patterns hold for T. celebensis is not established in the material at hand, so no precise courtship sequence, spawning trigger, or display is asserted for it here. The data are sparse, and the honest move is to note the genus-level context rather than invent species-level detail.
Breeding
No species-specific breeding account for Telmatherina celebensis — clutch size, egg type, incubation period, fry-rearing notes — was available in the cached sources, and none is invented here. Sailfin silversides are generally egg-layers whose adhesive eggs attach to substrate or vegetation by fine filaments, but the particulars vary across the family and have not been confirmed for this species in the references consulted.
T. celebensis is a Malili-lakes endemic that very rarely enters the aquarium trade, so there is little or no published hobby breeding experience to draw on — unlike the well-documented captive breeding of the unrelated Marosatherina ladigesi. The section is brief by necessity: the data are sparse, and saying less beats guessing.
In the aquarium
Telmatherina celebensis is only marginally an aquarium fish. FishBase notes a commercial aquarium use, but in practice the species is seldom kept, and the hobby's "Celebes rainbowfish" is the unrelated Marosatherina ladigesi, not this Malili endemic. The cached sources hold no established, species-specific husbandry for T. celebensis.
So no tank size, water-chemistry target, or temperature range is recommended here. The care parameters widely published for the hobby "Celebes rainbowfish" belong to M. ladigesi and must not be applied to this species without proper sourcing. Anyone who turns up genuine T. celebensis should treat it as a wild-type lake endemic of conservation concern and find primary, species-specific information before keeping or breeding it. With data this thin, caution beats borrowed assumptions.
Conservation
Telmatherina celebensis is assessed as Near Threatened (NT) on the IUCN Red List under criteria B1b(i,ii,iii,iv,v)+2b(i,ii,iii,iv,v) (version 3.1), in an assessment dated 14 June 2018. The species is endemic to the Malili Lakes Basin of Sulawesi, recorded from Lakes Towuti, Mahalona and Lontoa and the River Tominanga, with a small extent of occurrence (about 963 square kilometres) and area of occupancy (about 800 square kilometres). The population trend is reported as decreasing.
The main threats are overfishing; heavy sedimentation degrading the lake habitat; and the spread of the invasive flowerhorn cichlid (Cichlasoma trimaculatum and its hybrids) through the system, which is expected to cut subpopulations and mature individuals through predation and competition. Like the other Malili endemics, the narrow single-basin range leaves the species little resilience: pressure on Towuti, Mahalona or their connecting waters bears directly on the whole population. Near Threatened puts T. celebensis just short of a threatened category — a status the documented declines and habitat pressures make worth watching.