Taxonomy & naming
Xiphophorus mayae was described by Manfred Schartl and Axel Meyer in 2002, in the paper "Xiphophorus mayae, a new species of swordtail from Guatemala" (Ichthyological Exploration of Freshwaters 13(1):59–66). The species belongs to the genus Xiphophorus — the platies and swordtails — within the family Poeciliidae, subfamily Poeciliinae, of the order Cyprinodontiformes. Eschmeyer's Catalog of Fishes governs the valid name, treating Xiphophorus mayae Meyer & Schartl, 2002 as valid.
Within the genus, X. mayae sits in the southern swordtail clade built around Xiphophorus helleri, alongside X. helleri itself, X. alvarezi and X. signum. These are the long-sworded species of the southern part of the genus's range, distinguished from the platies and the more northern swordtails. A 2013 phylogeny of Xiphophorus (Kang, Schartl, Walter & Meyer, BMC Evolutionary Biology 13:25) examined the origin of the sword and placed the helleri-group species in their evolutionary context, the sword being an ancestral trait of the lineage rather than a repeated, independent invention.
The genus name Xiphophorus derives from the Greek xiphos, "sword," and pherein, "to carry," for the elongated lower caudal rays of the males. The species epithet mayae honours the Mayan people of Central America, in whose lands — the highlands and lowlands of Guatemala and adjacent Honduras — the fish occurs.
Morphology
Xiphophorus mayae is a large swordtail and the deepest-bodied member of the genus, with a fusiform but notably robust build; both sexes grow large, and females in particular become heavy, deep-bellied fish. FishBase records a maximum length of about 3 in SL, though with the male's caudal sword the total length is considerably greater — hobbyist accounts describe males reaching roughly 6–7 inches including the sword and females around 4.5 inches in body. Meristics give 14 dorsal soft rays, 9 anal soft rays, 28–29 vertebrae and no fin spines.
The colouration is the species' signature. Males show a metallic teal-to-green ground crossed by bright orange stripes along the flanks, with a dark midlateral band that runs continuously into the dark dorsal pigmentation of the sword. The sword itself is yellow-green, edged in a contrasting black margin, and about three-quarters of the caudal fin carries fine red striping. The overall effect resembles a selectively bred colour sword, yet it is entirely wild-type. As in all swordtails, the sword is formed from elongated lower caudal rays — rays 5–8 in this species — and is a male character.
The sexes are readily told apart. Males bear both the caudal sword and the gonopodium, the modified anal fin used in mating, and their pelvic fins reach to the middle of the gonopodium; females lack the sword, have a normal fan-shaped anal fin, and have pelvic fins reaching only to the base of the anal fin. Females are larger-bodied and far more robust than the slimmer, sworded males.
Habitat
Xiphophorus mayae is a freshwater, benthopelagic fish of tropical Central America, recorded from Guatemala and Honduras. It inhabits slower-moving, rocky rivers strewn with large black boulders, where the bottom is a mix of boulders, gravel and mud and the water at collection sites was described as grey in colour. Aquatic vegetation is a consistent feature of its habitat, dominated by reeds and Vallisneria.
The species favours the calmer, more vegetated reaches rather than open fast water. A well-known hobby strain originating from the Rio Belaire drainage in Honduras was collected not from the main river — which is rich in predators — but from a small pool fed by a runoff stream feeding into it, a refuge the fish appear to seek out. This preference for sheltered, plant-filled pools over predator-heavy main channels mirrors the structuring seen in other swordtails.
Thermally the fish is a warm-water tropical, with FishBase noting temperatures up to around 79 °F; aquarium accounts report tolerance of somewhat cooler conditions as well, broadly in the low-to-mid 20s Celsius. The water at its habitats tends toward neutral to hard, the kind of moderately mineralised water typical of the limestone-influenced drainages of the region.
Feeding
In the wild Xiphophorus mayae is an omnivore feeding low on the food web, with an estimated trophic level around 3.1. Its natural diet combines algae and aufwuchs grazed from rocks and plants, small insects and invertebrates, and decaying organic matter — the mixed plant-and-animal foraging characteristic of swordtails living among boulders and submerged vegetation.
In the aquarium the species is undemanding and readily accepts prepared foods, taking flake and pellets without hesitation, including vegetable or algae-based pellets that suit its partly herbivorous nature. A diet that includes a meaningful share of plant matter alongside small live and frozen invertebrate foods keeps the fish in good condition and supports its strong colour.
As with most poeciliids, varied feeding and steady grazing suit it better than infrequent large meals, and the species' robust appetite makes conditioning for breeding straightforward.
Mating
Like all poeciliids, Xiphophorus mayae practises internal fertilisation. The male transfers sperm to the female using the gonopodium — a slender intromittent organ formed from modified rays of the anal fin — rather than releasing milt over eggs. This is the defining reproductive innovation of the New World livebearers, and in the swordtails it is paired with the male's elongated caudal sword.
The sword is widely understood in Xiphophorus as a sexually selected ornament: the conspicuous tail extension functions in courtship and male-male interaction, and the trait has made the genus a model for the study of female preference and the evolution of male ornamentation. In X. mayae the male's vivid teal-and-orange flanks and black-edged sword form part of this courtship signal directed at females.
Females, as in related poeciliids, are able to store sperm internally, so that a single mating can fertilise more than one successive brood. This sperm storage, combined with internal fertilisation, lets isolated females continue to produce young after separation from males.
Breeding
Xiphophorus mayae is viviparous: after internal fertilisation the female carries the developing embryos and gives birth to free-swimming, fully formed fry rather than laying eggs. A distinctive feature of this species is that gravid females do not appear conspicuously pregnant — they neither swell dramatically nor "square off" in the abdomen the way many other poeciliids do, which can make their condition harder to read than in a guppy or platy.
Reported brood sizes vary. Hobbyist accounts cite drops of 20–40 fry, though one breeder observing the species directly recorded broods of up to about 16. The newborn fry are large and immediately able to swim and feed, but they are vulnerable to predation from tankmates and even adults, so dense planting or separate rearing improves survival; one breeder maintained a group at around 73–75 °F in a large tank for successful production. As is typical of the genus, sperm storage allows females to produce successive broods from earlier matings.
The species has not been reported to show superfetation — the overlapping gestation of multiple broods at different developmental stages found in some other poeciliid genera; in the swordtails reproduction follows the more usual single-brood gestation cycle, with the female carrying one developing brood at a time.
In the aquarium
Xiphophorus mayae is rated an easy fish to keep, with one important caveat: it is large and needs a large tank. Both sexes grow substantial, and males with their swords are long fish, so a minimum of a 36-inch tank — a 40-gallon breeder or larger — is recommended to house a group comfortably. In a tank that size the species is hardy and forgiving.
Water should be neutral to hard, reflecting the species' natural waters, at temperatures around 70–77 °F (70–77 °F); the fish tolerates somewhat cooler conditions and does not require especially warm water. Regular weekly partial water changes keep it in good health. A well-planted layout with Vallisneria or similar vegetation suits both its temperament and its habitat, and provides cover for fry.
This is a relatively recent addition to the hobby and not the most commonly seen swordtail, often circulated as specific collection strains such as the Rio Belaire, Honduras line. Its wild-type colour — metallic teal banded with orange and a black-edged sword — makes it a striking aquarium fish for keepers who can provide the space it needs.
Conservation
Xiphophorus mayae is assessed as Least Concern (LC) on the IUCN Red List, with the assessment dated 20 September 2019. The species is distributed across Guatemala and Honduras, and no major threats were flagged at the time of assessment. It is listed as harmless to humans and was not evaluated under CITES or CMS.
As a localised Central American freshwater fish, its long-term security depends on the health of the boulder-strewn, vegetated rivers it occupies, which in this region face the usual pressures of land-use change and water extraction. At present, however, the available assessment indicates a species of low conservation concern.
For aquarists, the responsible note is the standard one for any non-native livebearer: maintained hobby strains such as the Rio Belaire line should be kept and bred within the hobby and never released into local waters outside the species' native range, where adaptable swordtails can establish feral populations.