Taxonomy & naming
Gambusia punctata was described by Felipe Poey in 1854, the Cuban naturalist whose work laid the foundation for the study of the island's fishes. The species sits in the family Poeciliidae, subfamily Poeciliinae — the New World livebearers that include the guppies, mollies, swordtails and the mosquitofishes of the genus Gambusia. Eschmeyer's Catalog of Fishes treats Gambusia punctata Poey, 1854 as the valid name, and FishBase lists it under SpecCode 27649.
The genus name Gambusia is itself a Cuban coinage: it derives from the local term "gambusino," used in the phrase "fishing for gambusinos" to mean catching nothing at all — a wry reference to these small, easily overlooked fishes. The species epithet punctata is Latin for "spotted" or "dotted," describing the markings on the body. In English the fish is most often called the Cuban gambusia, while in the aquarium hobby it circulates under the evocative name "Blue Gambusia."
Morphology
Gambusia punctata is a comparatively large mosquitofish and a strongly size-dimorphic one. Females reach roughly 3 in in standard length, while males are markedly smaller, recorded to about 2 in SL — the sexes differing in size as is typical across the genus. The body is the sturdy, slightly upturned-mouthed form of a surface feeder, built for taking prey from the film and the upper water column.
The common hobby name, "Blue Gambusia," points to the cool, slightly bluish sheen that good condition brings out over the flanks, set against the fine spotting that gives the species its epithet. As in all poeciliids, the clearest external marker of sex is the male's gonopodium — the rod-like, modified anal fin used to deliver sperm internally — together with the male's smaller, slimmer build. Females are larger, deeper-bodied and plainer, developing the gravid fullness of a livebearer when carrying young.
Habitat
Gambusia punctata is endemic to Cuba, where it occupies a broad range of fresh waters: ponds, lakes and streams across the island. FishBase notes that it prefers stagnant or slow-flowing reaches and is typically found in schools close to shore, but it is not confined to the lowlands — it can occur in mountain streams up to about 1969 ft in elevation, a wider altitudinal span than many of its lowland relatives.
The water it lives in is warm and on the hard, alkaline side. Recorded conditions span roughly 75–82 °F with a pH of about 7.2 to 8.2, the mineral-rich profile of much of Cuba's karst-influenced freshwater. The species is a freshwater, benthopelagic, non-migratory fish. There is one notable footnote to its distribution: it has been reported to reach southern Florida from Cuba, apparently by crossing the Gulf Stream — a striking instance of natural dispersal for so small a fish, though Cuba remains its only true native home.
Feeding
Gambusia punctata is a carnivorous surface feeder, taking its prey at and just below the water film in the predatory manner characteristic of mosquitofishes. FishBase places it at a trophic level of about 3.3, consistent with a diet built largely on small animal prey — insects and their larvae, including the mosquito larvae that give the genus its reputation as a biological control agent, along with other small invertebrates drifting near the surface.
In the aquarium it should be fed as the active micro-predator it is. Small live and frozen foods — Daphnia, brine shrimp, mosquito larvae, finely chopped bloodworm — suit its feeding style, supplemented with good-quality flake or micro-pellets that it will take readily from the surface. Several small feedings a day match its near-constant grazing habit better than a single large meal, and a varied, animal-rich diet keeps both colour and breeding condition at their best.
Mating
Like all poeciliids, Gambusia punctata reproduces by internal fertilisation. The male transfers sperm to the female using the gonopodium, the intromittent organ formed from modified rays of the anal fin; there is no nest, no spawning site and no external egg-laying. Males of Gambusia are persistent rather than ceremonious, pursuing females and attempting copulation, and females are able to store viable sperm internally, so that a single mating can give rise to more than one successive brood.
Detailed courtship observations specific to G. punctata are sparse in the literature, and precise figures for this species are not well documented — data are sparse here, and the broad pattern is best read from the genus as a whole. What is consistent across Gambusia is the combination of a male gonopodium, internal fertilisation, female sperm storage and live birth, the suite of traits that defines reproduction in this fish and separates it from the egg-laying toothcarps it superficially resembles.
Breeding
Gambusia punctata is viviparous: the female carries the developing young internally and gives birth to free-swimming fry rather than laying eggs. Reproduction in Gambusia is lecithotrophic — the embryos are nourished by their own yolk rather than by a maternal placenta of the kind seen in some other poeciliid genera — so the female provisions her brood before fertilisation rather than feeding it through gestation.
In the hobby the species is bred much as other livebearers are, producing broods of fully formed fry that can swim and feed from birth, but it remains an uncommon, specialist fish; the Tropical Fish Hobbyist feature on the Blue Gambusia includes a dedicated section on breeding it while noting how rarely it is kept. Exact brood sizes and gestation lengths for G. punctata are not reliably recorded in the available sources, so they are left unstated here rather than guessed. As with most livebearers, dense planting or floating cover helps fry survive the adults, which will eat young given the chance.
In the aquarium
Gambusia punctata is a livebearer for the specialist rather than the beginner — not because it is delicate, but because it is uncommon in the trade and behaves like the active predator it is. The Tropical Fish Hobbyist account describes a fish that "moves with quick, jerky, darting motions, naturally drawing the observer's eye," and that restless, surface-oriented energy is the keynote of keeping it. It wants room to move and a securely covered tank, and it does best in groups, where it tends to school near the margins.
Water should reflect its native Cuban range: warm, in the region of 75–82 °F, and hard and slightly alkaline at a pH of roughly 7.2 to 8.2. Tankmates should be chosen with the fish's predatory disposition and Gambusia's general reputation for fin-nipping in mind — robust, similarly sized companions rather than long-finned or timid species. Given clean, stable, mineral-rich water and a varied diet of small live and frozen foods, it is a hardy and rewarding fish; its scarcity, not its demands, is what keeps it out of most aquariums.
Conservation
Gambusia punctata is assessed as Least Concern on the IUCN Red List, in an assessment dated 27 April 2020. As a widespread Cuban endemic occupying a range of freshwater habitats — ponds, lakes, lowland streams and mountain creeks alike — it is not considered to face a significant threat at the species level, and it is listed under neither CITES nor the CMS.
That said, the species' fortunes are tied entirely to Cuba's inland waters, and its altitudinal and habitat breadth is the kind of ecological flexibility that underpins a stable Least Concern listing. For aquarists the conservation message is the familiar one for hardy livebearers: a Cuban endemic should never be released into non-native waters, where an adaptable mosquitofish can establish itself readily. Within its homeland, G. punctata remains a common and secure component of the island's freshwater fish fauna.