Taxonomy & naming
Polypterus teugelsi was described by Ralf Britz in 2004, based on specimens first collected in 1988 from the upper Cross River drainage in Cameroon — one of the more recently described members of the ancient family Polypteridae, the bichirs and reedfish. The Polypteridae are the most basal living lineage of the ray-finned fishes (Actinopterygii), a branch that diverged from every other ray-finned fish deep in the fossil record; every species in the family, teugelsi included, is a genuine living fossil retaining ancestral features long since lost elsewhere among bony fishes. The Catalog of Fishes places it in genus Polypterus, order Polypteriformes.
The species epithet commemorates Guy Teugels, the Belgian ichthyologist well known for his work cataloguing the freshwater fishes of Central and West Africa. In the hobby it is generally sold, on the rare occasions it appears at all, as the Cross River bichir — a nod to its narrow home range — and it remains one of the least commonly seen bichirs in the aquarium trade, seldom imported and, per hobbyist accounts, essentially undocumented in established captive collections.
Morphology
Like every bichir, P. teugelsi carries the family's signature architecture: a long, cylindrical body sheathed in thick, interlocking ganoid scales — rhombic plates of bone capped with a hard, enamel-like layer — and a row of separate dorsal finlets, seven to nine of them in this species, running down the back in place of a single dorsal fin. The paired pectoral fins sit on fleshy, muscular lobes that the fish uses to prop itself and shuffle across the substrate. FishBase records a maximum recorded size of 16.3 in (standard length); Seriously Fish lists captive individuals reaching around 15.7 in.
The species is one of the more strikingly marked bichirs: an olive-brown back overlaid with a network of fine black markings, jet-black pectoral fins, and a warm orange belly, a combination that sets it apart from the plainer grey or barred patterns of relatives like the Senegal bichir. As in all Polypterus, eyesight is poor and the fish relies on smell to find food, and — the family's defining trait — it breathes air with a pair of primitive lungs, rising to gulp at the surface.
Habitat
Polypterus teugelsi is a narrow-range endemic, known only from the upper reaches of the Cross River drainage in Cameroon, close to the type locality where it was first collected. It inhabits densely shaded, slow-moving streams under closed rainforest canopy — a very different setting from the open floodplains favoured by wide-ranging relatives such as the Senegal bichir.
FishBase records water in the low-to-mid 20s °C, around 77–81 °F, and close to neutral, pH 7.4–7.5; Seriously Fish gives a slightly broader range of 77–82 °F and pH 7.0–7.5 with soft-to-moderate hardness (1–5 dH). Both point to the same picture: cool, shaded, gently flowing forest-stream water rather than the warm, turbid floodplain water many other bichirs tolerate.
Feeding
As in the rest of the genus, P. teugelsi is a carnivorous, largely nocturnal ambush predator that hunts by smell rather than sight, cruising close to the substrate after dark and engulfing prey with a quick sideways snap. FishBase specifically notes the species as nocturnal and carnivorous, consistent with the shaded, low-light streams it inhabits, where keen eyesight would count for little.
Detailed dietary records for wild teugelsi are not documented in available sources; based on the well-established feeding ecology of Polypterus generally, the wild diet almost certainly includes aquatic insect larvae, worms, crustaceans and small fish. In captivity — where the species is only very rarely kept — bichirs of this kind typically accept earthworms, prawn, mussel and other meaty foods, along with frozen bloodworm for juveniles.
Mating
Detailed courtship and spawning behaviour has not been documented for P. teugelsi specifically — Seriously Fish notes the species has not been bred in captivity — but the mechanics of bichir reproduction are consistent across the family. A courting male follows and nudges a ripe female, then cups his thickened, muscular anal and pelvic fins into a shallow pouch; the female releases a few small, adhesive eggs at a time into this cradle, and the male fertilises them there before they are scattered onto plants and the substrate.
Sexual dimorphism in Polypterus is chiefly this spawning apparatus: males carry a visibly broader, thicker anal fin than females. This has not been specifically confirmed in published accounts of P. teugelsi, but it is the diagnostic dimorphism throughout the genus and can reasonably be expected to hold here too.
Breeding
Polypterus teugelsi is, like every bichir, an egg-scatterer with external fertilisation and no parental care: eggs are deposited a few at a time onto plants and fine substrate, and adults will consume both eggs and fry if given the opportunity. Eggs are expected to hatch within a few days into larvae bearing feathery external gills behind the head — a larval feature shared across the family — which are absorbed as the young mature.
Seriously Fish states plainly that the species has not been bred in captivity, and it is not documented as farmed for the trade the way the Senegal bichir is. Given how seldom it is even kept, let alone spawned, captive-bred Cross River bichirs essentially do not exist; any specimen in the hobby should be assumed wild-collected.
In the aquarium
Polypterus teugelsi is exceptionally rare in the trade — Seriously Fish describes it as one of the least commonly seen bichirs, and it is a fish for the specialist rather than the casual keeper. As with every bichir, a completely secure, gap-free lid is non-negotiable: this is a determined escape artist that will exploit any opening, while the tank still needs an air gap at the surface for the fish to breathe. It should be treated as a predator that will eat any tankmate small enough to swallow, and is otherwise peaceful with similarly sized fish rather than a candidate for a small community tank.
Water should mirror its shaded forest-stream origin: a soft sand substrate, driftwood and cover for a nocturnal fish, dim lighting, and stable, near-neutral water in the mid-to-high 20s °C. Its thick ganoid armour makes it hardier and more tolerant of routine medications than scaleless catfishes, but given its Data Deficient status and total dependence on wild collection, prospective keepers should treat any specimen as a wild-caught, conservation-relevant animal and buy only from reputable, traceable sources.
Conservation
Polypterus teugelsi is assessed by the IUCN as Data Deficient, reflecting how little is known about its population size, trend or the full extent of any threats — not evidence that it is safe. FishBase records the assessment as dating from February 2009, and no updated review appears to have followed; that gap is itself informative for a narrow-range endemic.
The species' entire known range is a restricted stretch of the upper Cross River drainage in Cameroon, part of a wider Cross River basin recognised as a freshwater biodiversity hotspot under pressure from deforestation and agricultural conversion across the region. A single-basin endemic confined to shaded rainforest streams is inherently more exposed to local habitat loss than the continent-spanning bichirs of the Sudano-Sahelian rivers, even though no basin-specific threat assessment is available to quantify that risk.