Taxonomy & naming
Myloplus lucienae was described in 2016 by Marcelo Andrade, Renata Ota, Douglas Bastos and Michel Jégu in Zootaxa (4205(6): 571–580), based on a holotype (INPA 30717, 5 in SL) collected from the rio Carabinani, a rapid-fed tributary near Novo Airão, Amazonas, Brazil, at approximately 2°01'25"S 61°32'35"W. It belongs to family Serrasalmidae — the piranhas, pacus and silver dollars — within order Characiformes, and to the genus Myloplus, one of several genera (alongside Tometes and Ossubtus) split out of the older, broader genus Myleus as taxonomists worked to separate the true silver dollars from other deep-bodied serrasalmids. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) treats Myloplus lucienae as a currently valid species; any older literature or trade references to a Myleus-genus placement reflect the pre-2016 taxonomy and should be read as outdated.
The species epithet lucienae honours Luciene Maria Kassar Borges, as recorded by Andrade et al. (2016) in the original description. It has no established English vernacular name in wide use, which is typical of a species described only within the last decade and never established in the aquarium trade under a common name of its own; the genus as a whole is sold generically as "silver dollars."
Morphology
Myloplus lucienae has the classic silver dollar body plan: a laterally compressed, disc-like body with large scales and an elongated profile relative to some of its more rounded congeners, adapted for holding position and manoeuvring in fast-flowing rapids rather than sluggish backwaters. Andrade et al. (2016) note small prespelvic spines along the ventral midline, a feature shared across the genus and used alongside scale counts and fin-ray formulas to separate Myloplus species from one another and from the related genera Tometes and Ossubtus.
FishBase records a maximum size of 13.5 in standard length, a substantial adult size for a disc-shaped characin and one that should not be underestimated by anyone comparing it casually to small tetra-type schooling fish. As in other silver dollars, colouration is likely a silvery base with the possibility of darker fin or body markings, though detailed live-colour description beyond the original taxonomic account is not available in the cache for this species; prospective keepers should expect the general silver-dollar look — a bright, mirror-flanked disc — rather than any distinctive pattern confirmed for this species specifically.
Habitat
Myloplus lucienae is known from the rio Negro basin in the Brazilian Amazon, specifically from rapid, fast-flowing stretches of blackwater tributaries draining toward the Guiana Shield — the type locality on the rio Carabinani near Novo Airão is a rapids-associated habitat rather than a still floodplain lake. This places the species in the tea-dark, tannin-stained, mineral-poor water typical of the rio Negro system, though the cache does not provide directly measured pH or hardness values for the wild population.
Given its rio Negro blackwater origin and its placement among rapid-dwelling relatives, the species likely experiences soft, acidic, warm water with a strong current — consistent with the broader pattern for rio Negro serrasalmids — but keepers should treat exact wild water chemistry as inferred rather than directly documented for this particular species, and should look to the aquarium parameters below (drawn from the better-documented congener M. rubripinnis) as the practical guide.
Feeding
Myloplus, as a genus, is defined in the original description as fish adapted for plant-eating — the name itself reflects a herbivorous grazing habit, and the wider silver-dollar group is well documented as feeding on soft aquatic vegetation, algae, fallen fruit and seeds in the wild, with some incidental animal matter. There is no evidence in the available sources that Myloplus lucienae departs from this pattern.
In the aquarium, silver dollars in this genus take blanched greens (spinach, courgette, cucumber), spirulina-based foods and algae wafers as a dietary staple, with occasional protein such as bloodworm or brine shrimp rounding things out. Keepers should plan feeding — and tank planting — around the certainty that this is a grazing herbivore that will treat live aquarium plants as a standing food source, not an occasional risk.
Mating
No courtship behaviour has been documented specifically for Myloplus lucienae in the available sources. Silver dollars in this genus are not known for pronounced external sexual dimorphism, and pairs or spawning groups in the hobby are typically identified by behaviour and conditioning rather than by appearance. Data on this species is sparse enough that keepers attempting to breed it should expect to rely on general silver-dollar husbandry — conditioning a group on a rich, varied diet and softening and warming the water to encourage spawning readiness — rather than any species-specific account.
Breeding
Silver dollars in genus Myloplus are egg-scatterers: a conditioned pair or group releases eggs over fine-leaved plants or similar cover in soft, acidic water, with no nest built and no parental care afterward — the eggs and resulting fry are left to fend for themselves, in contrast to the substrate-guarding behaviour of true piranhas in the same family. This mode is occasionally achieved in the hobby for related Myloplus species under soft, acidic conditions, but Myloplus lucienae itself has no documented aquarium spawning record in the sources available here.
Given the total absence of species-specific breeding reports, this account states plainly that Myloplus lucienae should be treated as essentially unbred in the hobby at present. Anyone attempting it should expect to work from the general Myloplus template — soft, acidic, warm water and a well-fed group over fine plant cover — while recognising that success is undocumented for this particular species.
In the aquarium
At a documented maximum of nearly 13.5 in SL, Myloplus lucienae needs a genuinely large aquarium as an adult — this is not a fish for a modest planted community tank, and the footprint required scales with a disc-bodied fish of that size, not a slim characin. It is a schooling fish by genus-wide reputation and should be kept in a group rather than alone, in open swimming space with strong filtration to handle both its size and its voracious grazing.
The single most important care note, repeated across every silver dollar in this genus, is that it is a dedicated plant-shredder: any soft-leaved live plant will be eaten, often within days, so this is a fish for a robust, hardscaped tank with driftwood and rock rather than a soft aquascape. Feed a plant-forward diet (blanched vegetables, spirulina, algae wafers) with occasional protein, and expect this species — like its congeners — to be a peaceful, non-aggressive tankmate for other robust community fish, provided the tank is sized and planted (or deliberately not planted) with its herbivory in mind.
Conservation
Myloplus lucienae has not been formally assessed by the IUCN Red List and currently carries a status of Not Evaluated. Described only in 2016 and known from a limited number of rio Negro basin records, it is a poorly surveyed species rather than one of documented conservation concern, and the cache used for this account has no data on population trend or trade collection pressure.
As with many recently described, single-basin Amazonian serrasalmids, the practical conservation picture is one of data scarcity: the rio Negro basin faces general pressures from deforestation-linked sedimentation and development, but no species-specific threat assessment exists for Myloplus lucienae, and any statement about its trade status beyond "not established as a common aquarium fish" would be speculation the cache does not support.