Taxonomy & naming
Tometes camunani was described in 2013 by Andrade, Giarrizzo and Jégu from the upper rio Trombetas basin — the rio Mapuera, rio Cachorro and rio Erepecuru tributaries of the Guiana Shield in Pará, Brazil. The holotype (MPEG 23449, 9 in SL, a mature male) was collected from the rio Trombetas immediately upstream of Cachoeira Porteira. It belongs to the family Serrasalmidae — the piranhas, pacus and silver dollars — within the order Characiformes, in the genus Tometes, one of several silver-dollar lineages split out of the old, broadly defined genus Myleus as the family's taxonomy was revised; the Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the standing authority for the genus.
The species epithet "camunani" is not a Latin or Greek construction but a Wai-Wai indigenous name, chosen by the authors to honour the fish's cultural significance to the Wai-Wai and quilombola communities of the upper Trombetas, who share the rapids the species depends on. Tometes camunani is distinguished from its closest congeners, T. makue and T. lebaili, by a slight frontal concavity of the neurocranium, by having five dentary teeth versus six to eleven in other congeners, and by counts of 81–99 lateral-line scales and 12–26 prepelvic spines.
Morphology
Tometes camunani has the classic silver-dollar build: a deep, laterally compressed, disc-shaped body with a small head and a short, blunt snout adapted for grazing rather than biting prey. FishBase records a maximum length of 36 in SL for the species — reported alongside a holotype of 9 in SL and paratypes of 9–15 in SL, so most examined individuals are considerably smaller than that outlier figure, but the species is nonetheless a substantially larger fish than the small tetra-sized silver dollars often sold under that name.
Its digestive tract is notably elongated — 4.2 to 5.5 times standard length — a gut built for processing large volumes of fibrous plant material, consistent with its specialised rheophilic, herbivorous lifestyle. Colouration follows the general silver-dollar pattern of a bright, laterally flattened silver body, though fine-grained colour and fin detail beyond the original description are not documented in the sources reviewed here.
Habitat
Tometes camunani is strictly rheophilic, restricted to fast-flowing rapids and cataracts in the upper rio Trombetas drainage of the Guiana Shield — specifically the rio Trombetas itself above Cachoeira Porteira, and the rio Mapuera, rio Cachorro and rio Erepecuru tributaries in Pará, Brazil. This is a specialised, high-oxygen, high-current habitat quite different from the still floodplain lakes and backwaters many other serrasalmids occupy, and the species' distribution appears to be tightly tied to that lotic shield-river environment rather than the wider lowland Amazon.
Within its native range, the biggest documented threat is habitat alteration from hydroelectric dam construction, which converts the fast, oxygenated rapids the species depends on into slack impounded water — a direct loss of the specialised niche it is built for.
Feeding
Tometes camunani is a phytophagous herbivore, feeding primarily on Podostemaceae — the rheophyte "riverweed" plants that carpet submerged rock in fast-flowing rapids and are otherwise a difficult, fibrous, low-nutrient food source. Its elongated digestive tract (4.2–5.5× SL) is a direct anatomical signature of this diet, built to extract nutrition from large volumes of tough plant material rather than to digest flesh.
In the aquarium, this biology translates directly: silver dollars of this genus are almost entirely herbivorous and should be fed a vegetable-forward diet — blanched greens, spirulina and algae wafers — supplemented with a modest amount of protein. Kept underfed on plant matter, they will turn to any live plants in the tank, which is the core husbandry warning for the group.
Mating
No courtship or spawning behaviour specific to Tometes camunani has been documented in the sources reviewed here. General accounts of the silver-dollar group (the genus Tometes together with related genera such as Metynnis and Myloplus) describe egg-scattering pairs or small groups spawning over fine-leaved vegetation, with no elaborate courtship display recorded, but nothing at the species level exists for T. camunani specifically — this rheophilic, shield-river species has no aquarium breeding record to draw behavioural detail from.
Breeding
As a silver dollar, Tometes camunani would be expected to follow the pattern documented for its relatives in the genus: an egg-scatterer that spawns over fine-leaved plants, with no parental care of eggs or fry, and adults that will consume their own eggs if the eggs are not protected by dense vegetation or a fine substrate. That pattern is well established for the wider silver-dollar group, occasionally bred in the hobby in soft, acidic water conditions.
However, no aquarium or hobby breeding records exist for Tometes camunani itself. Its restriction to strong-current, high-oxygen rapids habitat makes it a poor match for typical still-water aquarium spawning setups, and it should be treated, honestly, as a species that is essentially unbred in captivity rather than assumed to reproduce readily on the general silver-dollar template.
In the aquarium
Tometes camunani is rarely if ever seen in the hobby, and anyone encountering it should size a tank to its real maximum size — FishBase's reported 36 in SL figure makes this a substantially larger, more demanding fish than the small silver dollars typically sold in stores, requiring a very large, robust aquarium rather than a modest planted community tank. Like other silver dollars, it is a schooling fish that should be kept in a real group and given open swimming space, but it is also a committed plant-shredder: any live plants in the tank should be assumed to be food, not decoration, so the tank should be hard-scaped with rock, wood and strong current rather than aquascaped with tender vegetation.
As a strictly rheophilic species from fast, well-oxygenated shield-river rapids, it would need strong water flow and excellent oxygenation to thrive, conditions that go beyond typical community-tank filtration. Diet should be vegetable-forward — blanched greens, spirulina and algae wafers, with modest protein supplementation — mirroring its wild diet of tough Podostemaceae riverweed. Given the total absence of aquarium breeding or long-term husbandry records, this is a species for a specialist rheophilic-fish keeper rather than a typical community aquarium.
Conservation
The IUCN Red List assesses Tometes camunani as Least Concern, an assessment dated November 2018 (valid as of Red List version 2022.2). This reflects that the species, while narrowly distributed, does not currently show evidence of significant population decline across its known range in the upper rio Trombetas shield-river system.
The more pressing long-term concern is habitat-specific rather than population-wide: the species is restricted to fast-flowing rapids in the rio Trombetas, rio Mapuera, rio Cachorro and rio Erepecuru, and hydroelectric dam construction in this part of the Guiana Shield is a direct threat to that specialised lotic habitat. Because Tometes camunani cannot simply relocate to slack impounded water the way habitat generalists can, dam development in the upper Trombetas drainage is the key watch item for the species' future status. The species also holds documented cultural importance to the Wai-Wai indigenous and quilombola communities who inhabit and depend on the same river system.