Taxonomy & naming
Pseudoxiphophorus cataractae was first described by the American ichthyologist Donn Eric Rosen in 1979, in his revisionary study "Fishes from the uplands and intermontane basins of Guatemala" (Bulletin of the American Museum of Natural History 162). Rosen placed it in the genus Heterandria, and the original combination Heterandria cataractae remains its basionym. The type series was substantial — Rosen reported on the order of two hundred specimens, a mix of young-to-adult males and females from the type locality — so the species was well characterised at its founding even though it has been little studied since.
The fish now sits in Pseudoxiphophorus, the genus into which most of the former Central American Heterandria have been moved. This reflects the modern understanding of the lineage: molecular phylogenetic work (for example Agorreta and colleagues, 2013) has clarified relationships among the poeciliid genera and supported separating the Central American radiation from the North American Heterandria formosa, the type species of that genus. Eschmeyer's Catalog of Fishes, the authority for valid names, accordingly treats the species as Pseudoxiphophorus cataractae (Rosen, 1979), with the authority in parentheses to mark the genus transfer.
The species belongs to the family Poeciliidae, the New World livebearing toothcarps, within the order Cyprinodontiformes. Its English name, Cobán toothcarp, points to its provenance near the city of Cobán in highland Guatemala; a Spanish common name, "bute," is also recorded. Both names are essentially geographic and descriptive labels rather than signs of any hobby presence — this is a wild endemic, not a trade fish.
Morphology
Pseudoxiphophorus cataractae is a small fish. FishBase gives a maximum standard length of about 2.5 in for males and unsexed specimens and 2.5 in for females, and the IUCN account similarly cites a maximum body size of roughly 2.5 in SL (following Lucinda, 2003). That places it among the larger members of its genus but still well within the modest size range typical of Central American poeciliids, the group that includes the spottail and other former Heterandria of the aquarium world.
Detailed published colour and meristic notes for this species are sparse outside Rosen's original description, so prose here stays close to what the genus reliably shows rather than guessing at this species' particulars. Like its relatives it is a benthopelagic stream fish — robust, fusiform, adapted to flowing freshwater — and as a poeciliid it is sexually dimorphic, with males bearing the modified anal-fin gonopodium and females reaching the larger maximum size. Beyond those genus-level certainties, fine details of patterning and fin shape for P. cataractae specifically are not well documented in the accessible literature, and we note the data as sparse rather than fill the gap.
Habitat
This is one of the most narrowly distributed livebearers known. Pseudoxiphophorus cataractae is endemic to Guatemala and has been collected only from its type locality: the Sachicha Arroyo, described by Rosen as a large, isolated jungle stream roughly twenty kilometres north-west of Cobán, in the department of Alta Verapaz. The arroyo is a tributary of the Senizo (Sanizo) River, itself part of the great Usumacinta drainage that feeds the Gulf of Mexico.
The defining feature of the habitat — and the origin of the name cataractae — is a thirty-metre ribbon waterfall that separates the Sachicha Arroyo from the Senizo River below. This cataract isolates the headwater stream and its fish fauna from the downstream system, a classic case of a waterfall acting as a biogeographic barrier and producing a localised endemic. The IUCN assessment gives both the extent of occurrence and the area of occupancy as on the order of four square kilometres, treating the species as occupying a single location.
The water is permanent freshwater stream and creek habitat, including the waterfall reach itself, set in lowland-to-upland tropical jungle. As a tropical Central American highland stream fish it lives in warm, flowing freshwater; precise temperature and chemistry figures for the Sachicha Arroyo are not published in the sources at hand, so the environmental envelope below is given conservatively from the tropical, benthopelagic, freshwater classification rather than from measured field data.
Feeding
No species-specific diet study for Pseudoxiphophorus cataractae was located, so its feeding ecology is inferred from its trophic position and its relatives. FishBase models a trophic level of about 3.0, which is consistent with the small-omnivore-to-micropredator habit typical of stream poeciliids: a mixed diet of aquatic invertebrates and insect larvae together with algae, diatoms and organic detritus grazed from the substrate and taken from the water column.
In a clear, flowing jungle stream a fish of this kind would be expected to take drifting and benthic invertebrates — including insect larvae such as those of midges and other stream insects — supplemented by the aufwuchs and detritus that coat rocks and submerged surfaces. Because the published record is thin, the diet is best described in these general terms; we avoid asserting specific prey items that have not been documented for this species.
Mating
Like all poeciliids, Pseudoxiphophorus cataractae is a livebearer with internal fertilisation. Reproduction does not involve spawning over a substrate; instead the male transfers sperm directly to the female using the gonopodium — a slender intromittent organ formed from modified rays of the anal fin, the structural hallmark of the family. Males pursue and attempt to inseminate females, and in poeciliids generally females can store viable sperm internally and produce successive broods from a single mating, though this has not been documented specifically for P. cataractae.
Detailed courtship behaviour for this species has not been described in the accessible literature. What can be stated with confidence is the mode of fertilisation and the presence of the gonopodium, both of which follow from the species' placement in Pseudoxiphophorus and the Poeciliidae. Beyond that — display patterns, mate choice, any sneak-mating tactics — the data are sparse, and we leave them unasserted rather than transpose another species' behaviour onto this one.
Breeding
Pseudoxiphophorus cataractae is viviparous: after internal fertilisation the female gestates the developing young and gives birth to free-swimming fry rather than laying eggs. This is the reproductive mode of the entire family and is not in doubt for this species, even though species-specific reproductive figures are lacking.
No gestation period or brood size has been published for P. cataractae itself. For scale, the better-known congener Pseudoxiphophorus bimaculatus is reported to carry young for roughly six to eight weeks and to produce broods of around twenty to a hundred young — but that is a genus-level analogy offered only for context, not a measurement for this fish, and the two should not be conflated. The size and frequency of broods in the Sachicha Arroyo population remain unknown. That Rosen's type series included a large number of young-to-adult individuals of both sexes at least confirms that the species reproduces successfully in its native stream and was locally abundant when collected.
In the aquarium
Pseudoxiphophorus cataractae is essentially absent from the aquarium hobby. It is a single-locality Guatemalan endemic with no established presence in the trade and no body of aquarist husbandry notes to draw on, so any keeping advice would be extrapolation from its relatives rather than experience with the fish.
What can responsibly be said is general and cautious. As a warm-water Central American stream livebearer, it would in principle want clean, well-oxygenated, flowing freshwater at tropical temperatures and a varied small-invertebrate-and-algae diet, like other Pseudoxiphophorus. But its conservation status and pinpoint range make this a fish to read about rather than to seek out: it is Vulnerable, known from one tiny location, and not a candidate for casual collection or trade. We deliberately give no care rating, because there is no reliable husbandry record for this species to base one on.
Conservation
Pseudoxiphophorus cataractae is assessed as Vulnerable on the IUCN Red List under criterion D2, in the assessment by McMahan, Quintana and Lyons (assessed 14 October 2019; published 2020). The listing rests on the species' extreme restriction: it is known only from the Sachicha Arroyo, with an extent of occurrence and area of occupancy each on the order of four square kilometres, treated as a single location. A population so confined is, by definition, vulnerable to any single adverse event affecting that one stream, even though the fish was reported as relatively abundant within the locality at the time of assessment and was re-collected during fieldwork in 2015, 2018 and 2019.
The threats identified are tied to that fragility. Potential future development of oil-palm plantations in the region could alter the local hydrology on which the isolated arroyo depends; abstraction of surface water for agriculture is a related concern; and recreation or eco-tourism around the waterfall carries some, currently low, impact. The site lies within no protected area. Nationally, the species has been listed in category 2 on Guatemala's threatened-species list (CONAP, 2009).
The conservation message is straightforward. A fish whose entire range is a few square kilometres of jungle stream behind a waterfall has no buffer against habitat change, and the responsible posture is protection of that single location rather than exploitation of it. For aquarists the practical implication is simply to leave wild populations undisturbed and to value the species through the literature and through any properly managed conservation effort, not through the trade.