Taxonomy & naming
Pseudoxiphophorus anzuetoi was described by Donn Eric Rosen and Reeve Maclaren Bailey in 1979, on the basis of material from eastern Guatemala. As is common in the poeciliids, the species has shifted in its generic placement over the decades: it was for a long time treated under Heterandria, the genus into which much of this group of Central American livebearers was historically folded, before the resurrection and broader application of the name Pseudoxiphophorus. Eschmeyer's Catalog of Fishes, the authority for valid names, recognises the combination Pseudoxiphophorus anzuetoi, with the original describers' names carried in parentheses to reflect that generic transfer.
The genus Pseudoxiphophorus sits within the family Poeciliidae, the New World livebearers — the group that also contains the guppies, mollies, platies, swordtails and mosquitofishes. Its members are small, internally fertilising, live-bearing toothcarps of Mexico and Central America. The species epithet honours Roderico Anzueto, a Guatemalan naturalist; FishBase records the species under SpecCode 53784 and traces much of its taxonomic treatment to Lucinda's 2003 checklist of the Poeciliidae in the freshwater fishes of South and Central America.
The English name on record for the species is the "Blue spotted Guatemala toothcarp," reflecting both its country of origin and its membership in the toothcarp assemblage. Beyond the formal description and survey literature, species-level documentation is sparse — it is not a fish that has accumulated the long synonymy or the hobby following of its better-known relatives.
Morphology
Pseudoxiphophorus anzuetoi is a small fish. FishBase gives a maximum length of about 2.5 in total length for males and unsexed specimens and up to about 3 in total length for females, the larger size of the female being the usual pattern in livebearing poeciliids, where the female must carry developing young internally. The body is the compact, somewhat deep-bodied form typical of the genus rather than the elongate shape of a swordtail.
As in all poeciliids, the sexes differ in the structure of the anal fin: the male's is modified into a gonopodium, a slender intromittent organ formed from elongated and specialised fin rays, used to transfer sperm to the female. This is the single most reliable feature for sexing the fish and is the anatomical signature of the family's internal fertilisation. The common name points to blue-toned spotting on the body, the colour cue that distinguishes it among the Guatemalan toothcarps.
Detailed published descriptions of live colour and fine meristics for this species are limited, and the hobby has produced little photographic record, so beyond the size figures and the generic body plan the morphological account is best kept conservative — data are sparse for this rarely kept species.
Habitat
The species is a Central American endemic of the Caribbean and Pacific slopes. FishBase records it from the Motagua River basin in Guatemala — across the departments of El Progreso, Zacapa, Chiquimula and Izabal — and from Copán in adjacent Honduras, as well as from the Lempa River basin in Guatemala. This is a distribution centred on the dry interior valleys and lowland reaches of eastern Guatemala, spilling over the international border to the east and reaching toward the Pacific drainage in the south.
The waters it occupies are warm and hard. FishBase reports a temperature range of roughly 21 to 26 degrees Celsius, a pH of about 7.0 to 7.6, and a hardness of around 5 to 15 dH — neutral to mildly alkaline, moderately mineralised water typical of the limestone-influenced streams of the region. The fish is described as freshwater and benthopelagic, occupying the middle and lower parts of the water column in these flowing tropical habitats.
Like many small Central American livebearers, it is presumably a fish of stream margins, pools, vegetated edges and slower runs rather than open fast current, but specific microhabitat data for P. anzuetoi are thin in the literature. What can be said with confidence is the climatic and chemical envelope: warm, hard, near-neutral to slightly alkaline tropical fresh water in the Motagua–Lempa basins.
Feeding
No published diet study exists for Pseudoxiphophorus anzuetoi specifically; FishBase assigns it an estimated trophic level of about 3.0, a figure derived from its size and from its relatives rather than from stomach-content analysis. That places it among the small omnivore–micropredators rather than the strict herbivores or the higher predators.
The poeciliids of this group are generalist feeders, and the genus Pseudoxiphophorus in particular tends toward an animal-leaning omnivory: small aquatic invertebrates, insect larvae, crustaceans and other drifting or benthic prey, supplemented by algae, biofilm and detritus taken from surfaces and the substrate. A fish of this size in a warm, productive stream would be expected to graze opportunistically on whatever small invertebrates and organic matter the habitat provides.
In the absence of species-specific records, the responsible summary is that P. anzuetoi is best regarded as an opportunistic omnivore in the typical poeciliid mould — its exact dietary balance in the wild is not documented.
Mating
Pseudoxiphophorus anzuetoi reproduces by internal fertilisation, the defining reproductive mode of the family Poeciliidae. The male's anal fin is modified into a gonopodium, the rod-like intromittent organ through which sperm is transferred directly to the female; there is no external egg-laying and no nest. This contrasts sharply with the egg-scattering and egg-tending strategies of most other freshwater fishes and is the reason poeciliids are collectively known as livebearers.
As in related livebearers, males are expected to pursue females actively rather than to defend territories, using the gonopodium for copulation; in many poeciliids females are also able to store sperm internally and produce a succession of broods from a single mating, though this has not been documented specifically for P. anzuetoi. The larger body size of the female reflects the demands of carrying developing embryos to term.
Species-specific courtship behaviour for P. anzuetoi has not been described in the literature, so the account here is drawn from the general biology of the genus and family. Superfetation — the simultaneous carrying of broods at different developmental stages, known in some poeciliid lineages — has not been documented for Pseudoxiphophorus and should not be assumed for this species.
Breeding
P. anzuetoi is viviparous: after internal fertilisation the female carries the developing young and gives birth to free-swimming fry rather than depositing eggs. No breeding study has been published for the species itself, so reproductive figures must be read from its congeners. The closely related twospot livebearer, Pseudoxiphophorus bimaculatus, gives a useful genus-level analog: it carries young through a gestation of roughly six to eight weeks, the length depending on the age and size of the female, and produces broods reported between about 20 and 100 young.
Those brood and gestation figures should be treated as genus-typical rather than as measured values for P. anzuetoi. The genus is composed of matrotrophic-leaning poeciliids — fishes in which the mother provides some nourishment to the developing embryos beyond the initial yolk — but the precise degree of maternal provisioning in this particular species is not documented.
The newborn fry of poeciliids of this kind are fully formed, free-swimming miniatures capable of feeding immediately, and in the wild they rely on dense cover at the stream margins to escape predators, including, as in many livebearers, the adults of their own kind. For P. anzuetoi specifically the data are sparse, and any quantitative breeding statement should be understood as inferred from the genus.
In the aquarium
Pseudoxiphophorus anzuetoi is essentially absent from the mainstream aquarium hobby; no dedicated species care or breeding profile could be located for it, and it is an uncommon, rarely kept Guatemalan and Honduran fish. What guidance can be offered is therefore general poeciliid husbandry matched to the conditions recorded for the species in the wild.
Those conditions point to hard, neutral-to-alkaline water: a pH of roughly 7.0 to 7.6, a hardness in the order of 5 to 15 dH, and a temperature of about 21 to 26 degrees Celsius. As with most hard-water livebearers, stability, cleanliness and well-mineralised water matter more than chasing exact numbers. A planted tank with cover at the margins would suit a small group and, importantly, would give any fry somewhere to hide, since livebearers commonly predate their own young.
Beyond that, the honest position is that this is a fish for the specialist livebearer keeper rather than the general aquarist — husbandry specifics for P. anzuetoi are not established, and the recommendations here are extrapolated from its wild water chemistry and from the behaviour of better-documented relatives in the genus.
Conservation
Pseudoxiphophorus anzuetoi is assessed as Least Concern on the IUCN Red List, in an assessment dated 14 August 2019 (IUCN taxon ID 125341119). The Least Concern listing, corroborated through FishBase and iNaturalist, indicates that the species is not currently considered to be at significant risk of extinction at the global level.
FishBase characterises the species as having high resilience, with an estimated minimum population doubling time of under fifteen months — a reflection of the rapid reproduction typical of small livebearers, which lends populations a capacity to recover from disturbance. The species is neither listed by CITES nor by the Convention on Migratory Species, both of which record it as not evaluated.
That said, P. anzuetoi has a relatively restricted Central American range confined to the Motagua, Lempa and Copán drainages, and small-ranged freshwater fishes of this region are exposed to the broad pressures of habitat alteration, water extraction and pollution that affect the watersheds of eastern Guatemala and western Honduras. The current Least Concern status reflects the species' resilience and apparent abundance rather than an absence of any local threat to its habitats.