Taxonomy & naming
Sternarchorhynchus curumim was described by de Santana and Crampton in 2006, one of a wave of new tube-snout species erected as the genus Sternarchorhynchus was revised and split apart from look-alike congeners. It belongs to the family Apteronotidae, the ghost knifefishes, within the order Gymnotiformes, the New-World electric knifefishes — a group of bony fish defined by an electric organ and a long ribbon-like anal fin rather than by any resemblance to typical aquarium fish. Apteronotidae are set apart from the rest of the order by an electric organ built from modified nerve cells rather than muscle tissue, which gives them the fastest, most refined electrical discharges of any knifefish family.
The genus Sternarchorhynchus is large — around 32 described species — and its members are collectively known as tube-snout ghost knifefishes for the elongated, downturned snout shared across the group. S. curumim was diagnosed from its many congeners on body and fin pigmentation together with meristic (fin-ray and scale-row count, though this family lacks scales) and morphometric measurements, in the original Zootaxa monograph. The specific epithet curumim is Brazilian Portuguese for "child" or "young boy", chosen by the describers in reference to the species' comparatively small size. These New-World gymnotiforms are not related to the Asian featherback or clown knifefishes (Chitala, Notopterus); the shared common name "knifefish" describes a similar body shape arrived at independently, not a family relationship. The Catalog of Fishes is the authority for the valid name.
Morphology
Like other Sternarchorhynchus, S. curumim has the classic tube-snout profile: an elongated, tubular, downturned snout tipped with a small mouth, set on a laterally compressed, blade-shaped body that tapers to a fine point at the tail. There is no dorsal fin and no separate tail fin; locomotion comes from a very long anal fin running along most of the underside of the body, undulated in travelling waves that let the fish move forward or backward with equal control — useful for backing out of the crevices and root tangles it forages in. The skin is entirely scaleless, as in all Apteronotidae.
The original description reports a maximum recorded size of around 7 in total length in females, making this one of the smaller members of a genus that includes considerably larger tube-snouts. Running beneath the skin along the body is the electric organ, paired with rows of electroreceptor pores that read the field it generates; Sternarchorhynchus as a genus is considered among the more refined electrosensory specialists in the family, consistent with a nocturnal, snout-probing lifestyle in dark water. Sexes are not reported to differ in external appearance beyond the larger size attained by females.
Habitat
Sternarchorhynchus curumim is known from the Rio Tefé, a blackwater-influenced tributary that joins the Amazon in the lowland Amazon basin of Amazonas state, Brazil — the type locality given in the original description is the main channel of the Rio Tefé itself. As a benthopelagic freshwater species it lives near the bottom of the water column rather than at the surface, in the flowing water of the river channel.
Congeners across Sternarchorhynchus are widespread through tropical South America — more than two-thirds of the genus's roughly 32 species occur in the Amazon basin across Bolivia, Brazil, Colombia, Ecuador and Peru, with others in Orinoco tributaries of Colombia and Venezuela, the Essequibo of Guyana, and the Maroni of French Guiana and Suriname — and a preferred temperature range around 23–28 degrees Celsius is reported across the group. S. curumim itself, however, is documented only from its Rio Tefé type locality, consistent with the many narrow-range endemics the genus has turned out to contain as it has been revised species by species. Like its relatives it is presumed nocturnal, active after dark in dim, tannin-influenced river water where electrolocation, not eyesight, does the work of finding food and avoiding obstacles.
Feeding
No dedicated feeding study exists for S. curumim, but its tube-snout morphology is a strong guide to its ecology: the elongated, downturned snout and small terminal mouth are built for probing into sediment, leaf litter and root tangles to extract small invertebrates, almost certainly aquatic insect larvae and other benthic prey, in the manner documented for other Sternarchorhynchus and for tube-snouted apteronotids generally. Foraging is expected to be nocturnal and guided substantially by electrolocation, letting the fish detect the faint electrical signature of buried or hidden prey in water too dark or turbid for vision to be of much use.
Because the species is not established in the aquarium trade, there is no hobbyist record of feeding behavior in captivity to draw on, and this account is necessarily built from genus-level ecology rather than direct observation of S. curumim.
Mating
Nothing specific to courtship in S. curumim has been published, but the electric organ discharge that defines Apteronotidae is known, from close study of family members such as the brown ghost knifefish, to carry social information — size, sex, species identity and readiness to spawn — and to be actively modulated during encounters between individuals. Apteronotidae as a family are wave-type discharge specialists, producing a continuous, quasi-sinusoidal signal in the roughly 200–2000 Hz range whose frequency, amplitude and waveform differ by sex and individual and which is shaped further by brief "chirps", momentary frequency shifts used as context-specific social signals. It is reasonable to expect S. curumim to use its wave-type discharge the same way in courtship and rivalry, but this has not been documented for the species itself, and no observation of an approach or pairing sequence has been published.
Breeding
There is no published breeding record for Sternarchorhynchus curumim, and the genus and family as a whole are rarely, if ever, bred in captivity — the source material for this species is a taxonomic description, not aquarium literature. As an apteronotid it can be expected to be an egg-layer, most likely scattering eggs among cover such as roots or submerged debris rather than guarding a nest, in line with what little is documented for better-studied relatives, but no parental care has been recorded for this species or its close congeners. Data is sparse enough that this section should be read as inference from family-level biology rather than a description of S. curumim itself.
In the aquarium
Sternarchorhynchus curumim is not an established aquarium fish; there is no meaningful hobbyist record of the species in the trade, and this account should not be read as husbandry guidance drawn from experience keeping it. Were it to appear, the family-level cautions that apply to every apteronotid would apply here too: it is scaleless and therefore unusually sensitive to ammonia and nitrate, and to copper-based or otherwise harsh medications, which need to be dosed with care or avoided. Its tube-snout, sediment-probing feeding style and nocturnal habits suggest it would need a soft substrate to forage in, dim lighting, and secure cover such as root tangles or pipes to retreat into by day, echoing the needs of the black ghost and other tube-snouts kept by specialists.
Given how little is known of this species' size, temperament and specific requirements beyond the original description, anyone encountering it in the trade should treat it as a specialist proposition rather than a routine community fish, and should not assume compatibility with small tankmates given the family's nocturnal, predatory foraging habits.
Conservation
The IUCN Red List assesses Sternarchorhynchus curumim as Least Concern, an assessment dated November 7, 2018. This reflects the absence of any documented major threat to the species rather than a wide range: S. curumim is a narrow-range Amazon endemic known from the Rio Tefé basin in Brazil, and species with this kind of restricted, single-river distribution are generally the members of their genus most exposed to localized pressures such as habitat change, pollution or damming, even where no such threat has yet been formally documented for them.
As with many recently split, poorly surveyed tube-snout species, the Least Concern status should be read with some caution: it describes the best current assessment against known threats, not an exhaustive population survey, and a species confined to one river system carries an inherent vulnerability that a wide-ranging relative does not.