Taxonomy & naming
Bedotia marojejy was described by Melanie L. J. Stiassny and Ian J. Harrison in 2000, in Fieldiana Zoology (new series, 97: 143–156), as one of a series of new Bedotia species recognised once the long-conflated Malagasy rainbowfishes were examined drainage by drainage. The genus Bedotia is the type genus of the family Bedotiidae, the Madagascar rainbowfishes, an endemic radiation within the order Atheriniformes. Eschmeyer's Catalog of Fishes records the valid name as Bedotia marojejy Stiassny & Harrison, 2000; because the species was described in Bedotia, where it remains, the authority carries no parentheses.
The genus name honours Maurice Bedot (1859–1927), the Swiss systematist and hydrozoan specialist long associated with the natural history museum of Geneva. The specific epithet marojejy is taken from the type locality, named for the Marojejy massif and the Parc National de Marojejy whose forested slopes feed the headwaters the species inhabits. Like most Bedotia, it is separated from its congeners less by dramatic external features than by drainage of origin, meristics, and subtle pattern. The genus turns over from one river to the next, each basin tending to hold its own form. In the adjacent Namorona drainage to the south, for instance, B. marojejy gives way to a distinct congener — a measure of how finely these fishes are partitioned across Madagascar's eastern rivers.
Morphology
Bedotia marojejy is a small rainbowfish, among the more diminutive members of its genus. FishBase records a maximum standard length of about 2 in in males and unsexed specimens and roughly 2 in in females, so this is a fish of a few centimetres rather than the larger Bedotia familiar from the trade. The body is fusiform and of normal proportions, oval in cross-section, with the divided dorsal fin characteristic of the rainbowfishes.
Meristic counts from the original description and FishBase include six dorsal spines, twelve to thirteen dorsal soft rays, about seventeen anal soft rays, and a low vertebral count of around thirty-four (including the terminal half-centrum). The one reliable pattern feature is a series of dark blotches running along the lateral midline. Internally, the gut is very short — on the order of a third of the body length — which points toward a carnivorous, insectivorous habit rather than a herbivorous one. Data on live coloration and on sexual differences in fin shape and pattern are thin for this rarely kept species; beyond the midline blotching and small size, fine colour description should be treated as uncertain.
Habitat
Bedotia marojejy is endemic to northeastern Madagascar and is known only from the Manantenina River, an affluent of the Lokoho River within the Lokoho river basin. This is an extremely restricted distribution: the IUCN assessment treats it as a single location, with an area of occupancy of roughly 20 mi² and an extent of occurrence of about 232 mi². Part of that range lies within Marojejy National Park, whose intact forest cover helps protect the limnological integrity of the upper and middle Lokoho.
The habitat is freshwater wetland in the strict sense — permanent rivers, streams, and creeks of the inland forest. FishBase lists the species as freshwater, pelagic, and tropical. Habitat data specific to B. marojejy are limited, but the broader Bedotia pattern and the forested-headwater setting point to clear, well-shaded, well-oxygenated flowing water draining a high-rainfall massif. The tiny range is the central fact of its ecology. With the fish confined to one river system, there is no large outlying population to buffer a local decline, and disturbances in the catchment translate almost directly into conservation risk.
Feeding
The clearest anatomical clue to this species' diet is its gut, which FishBase notes is extremely short — only about a third of the body length. In fishes, a short, simple gut is a strong correlate of carnivory, and here it suggests B. marojejy lives largely on animal prey rather than on plant or detrital material. A reported trophic level of roughly 2.8 is consistent with an insectivorous, micro-predatory diet.
In keeping with the genus, it is best read as a small surface- and mid-water predator taking aquatic insect larvae, small crustaceans, and terrestrial insects that drop onto the water in its shaded forest streams. No gut-content study of B. marojejy exists, so the picture comes from its anatomy, its trophic position, and the habits of better-studied congeners rather than from direct observation. The data are sparse, and any finer breakdown of prey would be guesswork.
Mating
Direct observations of courtship and spawning in Bedotia marojejy have not been documented in the accessible literature, and this section necessarily draws on the well-established reproductive pattern of the genus rather than on species-specific records. Bedotia rainbowfishes are egg-scatterers that deposit adhesive eggs onto fine-leaved aquatic vegetation, typically a few eggs at a time over an extended period rather than in a single large clutch.
As in other Madagascar rainbowfishes, males presumably court females with fin-spreading displays in flowing or still margins among plants, spawning spread across many days. No marojejy-specific account of pair behaviour, display coloration, or seasonal timing exists in the sources at hand, so treat these details as congener-based inference, not as confirmed for this species. Where the record is silent, it is more honest to say the data are sparse than to manufacture a courtship narrative.
Breeding
No published captive-breeding account specific to Bedotia marojejy was located, reflecting how rare the species is in aquaria. What can be said rests on the consistent breeding biology of the genus: Bedotia are substrate-spawning egg-scatterers that lay small numbers of adhesive eggs onto fine plant material — Java moss or comparable fine-leaved vegetation — over a prolonged spawning period, with no parental care. Eggs hang from the spawning medium by fine filaments, and the small fry require correspondingly small first foods.
In aquaria, congeneric Bedotia are generally undemanding substrate-spawners, and conservation breeding of Madagascar rainbowfishes is an active focus for zoos and aquariums because so many — this species among them — are threatened in the wild. For B. marojejy itself, incubation period, clutch size, and fry development go undocumented in the sources reviewed; any numbers offered would be borrowed from relatives rather than measured. The fish almost certainly follows the genus's prolonged egg-scattering pattern, but the particulars remain unrecorded.
In the aquarium
Bedotia marojejy is rare in the aquarium hobby, and no species-specific care literature from the established rainbowfish sources could be found; what follows is general guidance for the genus, to be applied cautiously rather than treated as marojejy-tested. Given its small adult size of under 2 in, this is a fish for a modest, well-planted, well-oxygenated aquarium with gentle to moderate flow that mimics its clear forest-stream origins, ideally kept as a group.
Congeneric Bedotia do best in clear, shaded, slow- to moderately-flowing water over sandy or rocky substrate with aquatic plants. They are active mid-water swimmers that want open lanes alongside planted cover. That short, carnivore-type gut argues for a diet heavy on small live and frozen invertebrates rather than a plant-based or flake-only regime. With no reliable water-chemistry figures or temperament notes for this species, an aquarist should aim for clean, cool-to-warm, flowing forest-stream conditions and watch the fish rather than lean on borrowed numbers. As a threatened, narrowly endemic species, it belongs in considered conservation-minded husbandry, not casual keeping.
Conservation
Bedotia marojejy is assessed as Endangered (EN) on the IUCN Red List under criteria B1ab(iii,v)+2ab(iii,v), version 3.1. The assessment was carried out on 26 May 2016 (assessor T. Ravelomanana; assessment e.T44465A58306140) and published in 2016, marking a worsening from the Vulnerable listing the species held in 2004. The population trend is decreasing, with a continuing and significant decline in mature individuals noted, and the fish is confined to a single location — an area of occupancy of about 20 mi² within the Manantenina/Lokoho system.
Two threats dominate the assessment. The first is habitat degradation through siltation: deforestation in unprotected parts of the catchment, especially the exploitation and river transport of rosewood, deposits sediment into the species' streams. The second is the invasive green swordtail, Xiphophorus hellerii, which the IUCN reports is taking over this species' habitat and may be preying on its eggs. The fish is also caught with mosquito nets by local people for consumption. Part of the range does fall within Marojejy National Park, which protects the forested watershed and the limnological integrity of the upper and middle Lokoho; the assessment stresses that halting the spread of X. hellerii is a priority for the species' survival. As a single-population endemic, B. marojejy has essentially no buffer against these pressures, which is why a fairly localised set of threats puts the whole species at risk.