Taxonomy & naming
Sternarchorhynchus guayaberensis was described in 2025 by Ochoa, Albornoz-Garzón and DoNascimiento in the journal Ichthyology & Herpetology, based on specimens from tributaries of the Guayabero River in Colombia's upper Guaviare drainage, part of the Orinoco basin. It belongs to the family Apteronotidae, the ghost knifefishes, within the order Gymnotiformes, the New-World electric knifefishes — a bony but highly unusual group defined by an electric organ and a long anal fin used for locomotion in place of a normal tail. Apteronotidae are set apart within the order by an electric organ built from modified nerve cells rather than muscle, giving them the fastest, most refined electric discharges of any knifefish.
The genus Sternarchorhynchus is the 'tube-snouted' lineage of ghost knifefish, distinguished by an elongated, downturned snout used for probing the substrate. Phylogenetic analysis in the description places S. guayaberensis as the sister species to S. yepezi, in a clade alongside S. higuchii and S. mendesi — a group of congeners that share a pattern of narrow, localized distributions rather than the wide ranges seen in some other gymnotiforms. The species is separated from its relatives by a lightly colored mid-dorsal stripe, a dusky anal fin, 172–186 total anal-fin rays, and 16 precaudal vertebrae. As with all valid names in this atlas, the Catalog of Fishes is treated as the standing authority. The New-World knifefishes are unrelated to the Asian featherback and clown knifefishes (Chitala, Notopterus), which merely converge on a similar blade-bodied shape.
Morphology
Like other members of its genus, Sternarchorhynchus guayaberensis has the classic tube-snout ghost knifefish build: an elongated, laterally compressed, scaleless body tapering to a fine tail, with no dorsal fin and no conventional caudal fin. Movement comes from a long anal fin run in a continuous wave along the underside, letting the fish glide forward or backward with equal control — useful for backing out of narrow cover headfirst-out. The snout is drawn out and gently decurved, an adaptation shared across the genus for probing crevices and soft substrate for hidden prey.
The description distinguishes S. guayaberensis from its close relatives by a lightly colored stripe running along the mid-back, a dusky (darkened) anal fin, and fin-ray and vertebral counts — 172 to 186 rays along the anal fin and 16 precaudal vertebrae. Detailed data on maximum size were not reported in the cache available for this account; congeners in the genus range from under 8 in (S. mendesi) to over 15.5 in (S. oxyrhynchus) in total length, so size in this species should be treated as data sparse pending further study. Running the length of the body is the neurogenic electric organ characteristic of Apteronotidae, producing a continuous wave-type discharge, with sensory pores across the skin reading the resulting field back.
Habitat
The species is known from tributaries of the Guayabero River in the upper Guaviare drainage, part of the Orinoco basin in Colombia — a single-river system in South America's eastern Andean foothills. The description characterizes its distribution as putatively narrow and endemic, in keeping with several of its closest relatives (S. higuchii, S. mendesi), which are likewise known only from restricted stretches of river rather than broad basin-wide ranges.
As with other Sternarchorhynchus, it is reasonable to expect a fish of flowing, well-oxygenated river channels rather than still water, foraging along the bottom among sediment, roots and submerged structure. Congeners in the genus favor warm, soft to moderately mineralized, near-neutral water, and — as with all gymnotiforms — dim or turbid conditions suit their electrosensory lifestyle better than bright, clear water. Specific water chemistry data for the Guayabero population were not available in the sources reviewed for this account and should be treated as data sparse.
Feeding
No feeding studies specific to Sternarchorhynchus guayaberensis have been published; its diet can only be inferred from its genus. Sternarchorhynchus species use their elongated, decurved snout to probe crevices, leaf litter and soft substrate for aquatic insect larvae and other small invertebrates, detecting prey largely through electrolocation rather than sight — an approach shared with the rest of the tube-snouted ghost knifefishes and consistent with a nocturnal, benthic hunting style across the family.
Because this species is not established in the aquarium trade, there is no husbandry record of feeding behavior or accepted foods in captivity. Any captive account would need to start from the genus's general pattern — meaty, live or frozen invertebrate foods offered after dark — rather than from direct evidence for this species.
Mating
Nothing has been published specifically on courtship or mate choice in Sternarchorhynchus guayaberensis; the description covers taxonomy and morphology, not behavior. Across Apteronotidae generally, however, the continuous wave-type electric organ discharge is known to carry information about a fish's identity, sex and readiness to spawn, and in the best-studied species (the brown ghost, Apteronotus leptorhynchus) males and females shift discharge frequency during courtship in a kind of electrical duet. It is reasonable to expect a broadly similar role for electric signaling in this species' courtship, but that inference is drawn from the family, not from direct observation of S. guayaberensis, and should be read as such.
Breeding
There is no breeding record for this species — it was described in 2025 and is not present in the aquarium trade. Across Apteronotidae as a family, reproduction is by egg-laying, spawning is thought to occur among cover such as roots and crevices, and no substantial parental care has been documented in any well-studied species; most trade gymnotiforms are wild-caught or, where farmed, produced under hormone induction rather than natural spawning in captivity. Given the complete absence of husbandry or field-breeding data, this genus- and family-level pattern is the most that can honestly be said; the species' own reproductive biology is data sparse.
In the aquarium
Sternarchorhynchus guayaberensis is not a hobby fish — it has no presence in the aquarium trade and was described from scientific specimens only. Its congeners in the tube-snout group are themselves rarely seen outside specialist and public-aquarium collections, and where offered are typically wild-caught rather than captive-bred. Any theoretical care approach would need to borrow from the broader family: like all Apteronotidae it is scaleless, which makes gymnotiforms unusually sensitive to ammonia and nitrate and intolerant of copper-based medications, and like other tube-snouted Sternarchorhynchus it would be expected to need warm, well-oxygenated, dimly lit water with soft substrate and cover to probe.
Given the species' apparent narrow-endemic range and its very recent description, there is no ethical or practical case for collecting it for the trade, and no established husbandry protocol exists. This account is included for completeness of the genus, not as a guide to keeping the fish.
Conservation
Sternarchorhynchus guayaberensis has not yet been evaluated by the IUCN Red List — it was described too recently, in 2025, for an assessment to exist, and its status is properly recorded as Data Deficient rather than assigned a threat category. The description notes a putatively narrow, endemic distribution restricted to tributaries of the Guayabero River in the upper Guaviare drainage, a pattern shared with several of its closest relatives in the genus. Single-river endemics of this kind are, as a class, more exposed to habitat change, damming, deforestation and pollution than widely distributed gymnotiforms, simply because they have nowhere else to go — but no population data, trend, or direct threat assessment exists yet for this species specifically, and none should be assumed. Future field surveys and a formal IUCN assessment would be needed to say anything more concrete.