Taxonomy & naming
Apteronotus spurrellii was described by Regan in 1914, originally in the genus Sternarchus, and was reassigned to Apteronotus as part of Mago-Leccia's 1994 revision of the ghost knifefishes. It belongs to the family Apteronotidae within the order Gymnotiformes, the New-World electric knifefishes — bony fish, but unusual ones, defined by an electric organ and a single long anal fin used for propulsion rather than a normal tail and dorsal fin. 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 wave-type electric organ discharge (EOD) of any knifefish group; that discharge is used both to electrolocate prey and obstacles and to signal identity and sex to other fish.
The species has been treated as part of the Apteronotus leptorhynchus species-group, the brown-ghost complex, in phylogenetic work on the genus. The genus name Apteronotus comes from the Greek a- (without) + pteron (fin) + notos (back) — "without a fin on the back" — describing the absent dorsal fin shared by all ghost knifefishes. The species epithet honours H. G. F. Spurrell (1877–1918), a British physician and zoologist who collected fish in Colombia and Ghana in the early twentieth century. As with all valid names on this site, the Catalog of Fishes is treated as the authority.
Morphology
Apteronotus spurrellii reaches a documented maximum of about 10.5 in total length, distinctly smaller than the black ghost's roughly 19.5 in. Like other ghost knifefishes it has the family's diagnostic body plan: a laterally compressed, blade-like trunk tapering to a slender tail, no dorsal fin, and a very long anal fin — reported at 164–178 soft rays in this species — that ripples in travelling waves to drive the fish forward or backward with equal ease. The skin is scaleless and smooth, a trait shared across the order and one that carries real consequences for how the fish must be kept.
Running beneath the skin along the body is the electric organ, and the surface is studded with electroreceptor pores that pick up distortions in the field it generates. Fine details of coloration and markings for this species are not well documented in the sources available; readers should not assume it matches the black ghost's white-saddle-and-blaze pattern, since ghost knifefish species vary in this respect and data for A. spurrellii specifically is sparse.
Habitat
This species is known from the Río San Juan, a Pacific-slope river system in Colombia west of the Andes — a trans-Andean drainage rather than part of the Amazon or Orinoco basins that hold most of its relatives. It is described as benthopelagic in freshwater, meaning it lives and forages near the river bottom and in midwater above it rather than at the surface. As a single-river endemic, its known range is narrow by the standards of the genus, and its habitat requirements are inferred largely from the wider biology of Apteronotidae rather than from targeted study of this species.
Ghost knifefishes in general favor warm, soft, often tannin-stained flowing water — river channels and creek margins with cover from roots and leaf litter — and are active mainly at night, when their electric sense gives them an advantage over sight-hunting predators and competitors alike. There is no specific published water-chemistry data for A. spurrellii in the sources reviewed here; any aquarium parameters would have to be extrapolated cautiously from the family.
Feeding
No species-specific dietary study is available for Apteronotus spurrellii, but its family's feeding ecology is well established and there is no reason to expect this species differs. Ghost knifefishes are nocturnal carnivores that hunt small invertebrates and occasionally small fish, locating prey largely by electrolocation — detecting the faint electrical signature of an animal hidden in sediment, leaf litter or root tangles rather than relying on eyesight. They forage actively over the substrate after dark rather than lying in ambush.
Given this is essentially unrecorded in the trade, there is no first-hand aquarium feeding account to draw on for A. spurrellii specifically. Data sparse.
Mating
As in other Apteronotidae, the wave-type electric organ discharge almost certainly plays a central role in courtship and mate recognition in this species, since EOD signalling of sex and identity — and frequency shifts during courtship interactions — is a defining, well-studied feature of the Apteronotus leptorhynchus species-group to which A. spurrellii has been linked. Beyond that inference from its close relatives, no direct observation of courtship behaviour in A. spurrellii is documented in the available sources.
Data sparse: nothing specific to this species' spawning approach, pair formation, or site selection has been recorded in the literature reviewed here.
Breeding
Apteronotus spurrellii is not known to have been bred in the aquarium — unsurprising, since it barely appears in the hobby at all. Ghost knifefishes as a group are egg-layers that are only rarely bred in captivity; most trade specimens across the genus are wild-caught or, for the handful of commercially farmed species, produced under hormone induction rather than natural spawning in home tanks. Where spawning has been documented in the family it involves eggs scattered among roots or other cover, with no meaningful parental care afterward.
No breeding protocol exists for this species and none should be assumed. The honest statement is that A. spurrellii is essentially unbred and poorly documented in captivity; parental care, if any occurs, is not recorded.
In the aquarium
Apteronotus spurrellii is not an established aquarium fish; it does not appear to be part of the regular ornamental trade, and specific keeping guidance for the species does not exist in the literature reviewed. What can be said comes from its family. Like all Apteronotidae, it is scaleless and therefore needs great care with medications — copper-based treatments and full-strength doses of many standard remedies are risky — and it would be sensitive to ammonia and nitrate, requiring mature filtration and clean, warm, soft to moderately mineralized water.
As a nocturnal predator that hunts by electrolocation, any specimen kept would need a dim, well-covered tank with hiding places such as pipes, caves or root tangles, and should not be trusted with bite-sized tankmates after dark. Given how little is documented about this narrow-range Colombian endemic, prospective keepers should treat it as a specialist proposition and prioritize captive-bred or responsibly sourced stock, which for this species may not exist at all.
Conservation
The IUCN Red List assesses Apteronotus spurrellii as Vulnerable, an assessment from 2014 made under criterion B1ab(iii) — restricted geographic range combined with an ongoing decline in the extent or quality of its habitat. That status fits the pattern seen elsewhere in Gymnotiformes: wide-ranging Amazonian and Orinoco species tend to be secure, while narrow-range single-river endemics like this one are the vulnerable ones.
A. spurrellii is known only from the Río San Juan drainage on Colombia's Pacific slope, a region subject to deforestation, mining and other land-use pressure that can degrade water quality and habitat structure in exactly the way the assessment criterion describes. With no aquarium trade drawing on it, habitat protection in the Río San Juan basin — not collection pressure — is the relevant conservation lever for this species.