Taxonomy & naming
Micralestes occidentalis was originally described by Albert Günther in 1899 under the name Petersius occidentalis, with the type locality given as the Kotchwah River, Gold Coast (now Ghana). Syntypes are held at the Natural History Museum, London (BMNH 1899.12.22.32–36). The species was subsequently transferred to the genus Micralestes, a placement confirmed by Eschmeyer's Catalog of Fishes (California Academy of Sciences), which treats Micralestes occidentalis (Günther, 1899) as the valid name; the parenthetical authority reflects the original placement in a different genus.
Micralestes is a genus of small alestid tetras whose centre of diversity lies in sub-Saharan Africa. The family Alestidae — sometimes called the African characins or African tetras — is the sister group of the South American Characidae in the traditional arrangement, though molecular studies have progressively refined the internal phylogeny of the order Characiformes. Within Alestidae, Micralestes is distinguished by its small size, silvery compressed body, and characteristic schooling behaviour in open water over sandy or pebbly substrates. M. occidentalis represents the western extent of a genus otherwise more diverse in central and eastern African river systems, which is the sense captured by the epithet occidentalis.
Morphology
Micralestes occidentalis is a small, slender-bodied characin reaching a maximum total length of approximately 3 in, though most wild and aquarium specimens are somewhat smaller. The body is laterally compressed and fusiform — typical of open-water schooling tetras — with a pointed snout, moderately large eye, and a forked tail. The overall coloration is silvery, with a faint iridescent lateral stripe running from behind the operculum toward the caudal peduncle; the flanks may show a pale gold or greenish sheen under good lighting.
The fins are relatively unspecialized: a small adipose fin is present, as in all characins, and the caudal fin is clearly forked. Males and females are difficult to distinguish in the field, though females may appear deeper-bellied when gravid. No striking sexual dichromatism is reported. The species shares the general Micralestes gestalt of a trim, fast-moving, silvery schooling fish rather than the bold pattern characteristic of many West African alestids such as Congo tetras or African red-eye tetras.
Habitat
The species occupies a broad swath of West and Central African freshwater, recorded from river systems in Sierra Leone, Liberia, Côte d'Ivoire, Ghana, Cameroon, and the Congo drainage, as well as in the savanna-zone upper reaches of the Niger and Volta river systems. This inland savanna distribution sets it apart from many strictly coastal-forest alestids and indicates tolerance of the more seasonal, open-country rivers of the Guinea and Sudanian savanna zones.
M. occidentalis is described as a freshwater pelagic species — it schools in open water rather than hugging the substrate or dense vegetation. Water parameters from its range span a moderately wide envelope: temperature 72–79 °F, pH 5.5–7.5, and hardness 1–10 dH. These conditions describe the slightly soft, weakly acidic to neutral water characteristic of West African savanna rivers and their flooded margins during the wet season, when many characins disperse to feed and spawn.
Feeding
Micralestes occidentalis is an omnivore with a diet centred on small invertebrates and plant material. Documented food items include small crustaceans, aquatic and terrestrial insects, and aquatic plant matter — a mix consistent with opportunistic feeding in the water column and at the surface, typical of schooling alestids that patrol open water in search of whatever is seasonally abundant.
In the aquarium the species accepts a broad range of foods without difficulty. Good-quality micro-pellets and fine flake provide a staple, but condition and colour are best maintained with regular offerings of frozen or live invertebrates — Daphnia, brine shrimp nauplii, micro-worms, and small bloodworm all suit the fish's size and feeding mode. Like many active schooling tetras it feeds constantly in small amounts throughout the day and benefits from multiple small feedings rather than one large daily meal.
Mating
Micralestes occidentalis is oviparous and spawns seasonally in the wild, with reproduction associated with the warmer, higher-water conditions of the wet season — the pattern typical of savanna-zone West African characins that use rising water levels and food abundance as spawning cues. It is an egg-scattering open spawner: adults aggregate and release eggs freely into the water column or among fine-leaved aquatic vegetation, without nest building or territory defence.
No parental care is provided; adults take no interest in eggs or larvae after spawning and will consume eggs they encounter. Courtship displays, if any, have not been described in detail in the literature, but the pattern of group spawning and scattering among vegetation is consistent with other small alestids. In the aquarium, conditioning groups with live and frozen foods and providing temperature stability with a slight warm-season rise encourages spawning behaviour.
Breeding
As an egg-scattering alestid with no parental care, M. occidentalis follows the standard small-tetra breeding model in captivity. A conditioned group in a well-planted aquarium or a tank fitted with fine-leaved spawning plants or synthetic mops will deposit adhesive eggs among the vegetation, especially during morning hours. Raising water temperature slightly into the upper part of the species' range (toward 79 °F) and performing water changes with slightly warmer, soft water mimics the wet-season cue.
Eggs and adults should be separated promptly after spawning to prevent predation. Incubation at 75–79 °F takes approximately 48–72 hours for a small alestid of this size, with larvae becoming free-swimming a few days after hatching. First foods are infusoria and commercial liquid fry preparations, transitioning to newly hatched brine shrimp as the fry grow. Detailed captive-breeding accounts for this particular species are sparse in the hobby literature, so keepers should draw on the protocols established for closely related Micralestes species and other small West African alestids.
In the aquarium
Micralestes occidentalis is a gregarious schooling fish that should be kept in groups of at least eight to ten individuals; smaller numbers lead to skittish behaviour and the fish never display their natural open-water schooling movement. A tank of 31.5 in or more in length with a long, clear swimming lane is appropriate for an adult group. Décor can include fine sand, some smooth stones, and background planting of fine-leaved or feathery plants, leaving the central water column open.
Water conditions should reflect the species' West African savanna-river origins: temperature 72–79 °F, pH 5.5–7.5, and soft to moderately hard water. The species is hardy within this range and does not demand extremely soft or acidic water. Good filtration, regular water changes, and moderate surface agitation suit it well. Suitable tankmates include other peaceful, similarly sized West African species — other small alestids, dwarf cichlids, or West African killifish — as well as unrelated tetras and small rasboras of similar temperament. The species is not commonly encountered in the trade but makes an attractive and active subject for a West African biotope aquarium.
Conservation
Micralestes occidentalis has been assessed as Least Concern (LC) on the IUCN Red List, reflecting its wide distribution across multiple West and Central African river basins and its apparent tolerance of the range of conditions found in savanna and forest-margin freshwaters. The species is not considered to face immediate range-wide threat, and no significant population declines have been reported in the primary literature.
As with all West African freshwater fishes, background pressures include deforestation and catchment degradation, artisanal fishing pressure, and the increasing frequency of drought and flood extremes associated with climate variability in the Sahel and Guinea savanna zones. None of these pressures is currently considered to threaten the species at the global scale given its broad distribution. Routine monitoring as part of West African freshwater biodiversity assessments would be the appropriate precaution for a species whose ecology and population dynamics remain poorly studied.