Taxonomy & naming
Polypterus polli was described by Jean-Pierre Gosse in 1988 and is placed in the genus Polypterus, family Polypteridae, order Polypteriformes. The Polypteridae — the bichirs and the reedfish — are the most basal living lineage of the ray-finned fishes (Actinopterygii), a branch that split away from every other living ray-finned fish deep in the fossil record; they are genuine "living fossils," retaining ancient features — ganoid armour, paired lungs, larvae with external gills — that the rest of the group lost long ago.
The common name, Poll's bichir, is a patronym: the species epithet polli honours a Congo-basin ichthyologist named Poll, following the long-standing practice among African-fish taxonomists of naming new species for colleagues who worked the same rivers. As with several Congo bichirs, P. polli was distinguished from its close relatives on the basis of fin-ray and finlet counts and other meristic detail rather than colour pattern, which is often subtle across this genus.
Morphology
Poll's bichir shows the classic bichir body plan: an elongated, near-cylindrical body sheathed in thick, glossy, interlocking ganoid scales — rhombic plates of bone finished with a hard, enamel-like layer — that form a flexible suit of armour rather than the soft overlapping scales of most bony fishes. In place of a single dorsal fin it carries a row of separate finlets, each a short spine trailing a membrane flag; FishBase records 5 to 7 dorsal finlets in this species, alongside 14 anal soft rays and 50 to 56 vertebrae, the kind of meristic detail used to tell the Congo bichirs apart. The paired pectoral fins sit on fleshy, muscular lobes that the fish uses to prop itself up and shuffle along the substrate.
FishBase lists a maximum size of about 12.6 in standard length for males and unsexed fish, and aquarium sources describe specimens reaching roughly 11.8 in or more in the trade — a modest size within the genus, well short of giants like the Congo bichir. As in the rest of the family, eyesight is poor and hunting relies on a well-developed sense of smell; behind the gills lies a pair of primitive lungs that let the fish breathe air gulped at the surface, a trait it cannot do without — a bichir cut off from the surface can drown.
Habitat
Polypterus polli is centred on Malebo Pool (the wide, island-studded stretch of the Congo River between Kinshasa and Brazzaville) and the lower to central Congo basin, a region of warm, slow-moving to sluggish African rainforest river habitat. FishBase describes its water as soft and slightly acidic, consistent with the tea-stained, mineral-poor rivers typical of much of the Congo system.
As a nocturnal, bottom-oriented fish, it spends daylight hours sheltering among submerged wood, roots and vegetation along the margins of the pool and river, emerging after dark to hunt over sand and mud substrates. Its air-breathing lungs are a useful adaptation to the warm, sometimes oxygen-poor backwaters and flooded margins found through its Congo basin range.
Feeding
Poll's bichir is a carnivore and a nocturnal, bottom-feeding ambush predator, in keeping with the rest of its genus. With weak eyesight but an acute sense of smell, it hunts mainly by scent, moving slowly over the substrate after dark and locating prey before engulfing it with a fast sideways snap of the jaws. Wild diet is presumed to follow the general bichir pattern of aquatic invertebrates, worms and any small fish or animal it can swallow, though species-specific dietary studies are sparse.
In the aquarium it takes meaty foods readily — frozen or live bloodworm and earthworms are commonly used — and, like other bichirs, is a slow, deliberate feeder that can be outcompeted by faster tankmates at feeding time, so many keepers feed it after dark or place food directly within its reach.
Mating
Detailed courtship observations specific to Polypterus polli are not well documented, but bichirs as a family share a distinctive reproductive mechanism, and there is no indication this species differs. A male follows and nudges a ripe female, and the pair swim together among cover; the male then cups his thickened, muscular anal and pelvic fins into a shallow pouch, into which the female releases a few eggs at a time for the male to fertilise externally. The small, adhesive eggs are then scattered onto plants and the substrate, with the sequence repeated over an extended spawning bout.
As in other Polypterus, the sexes are told apart chiefly by this spawning apparatus — males carry a broader, thicker anal fin than females, particularly in breeding condition — rather than by colour or pattern, which differs little between the sexes.
Breeding
Like the rest of the family, Polypterus polli is an egg-scatterer with external fertilisation and no parental care: eggs are deposited among plants and left, and adults will consume both eggs and fry if given the chance. Eggs are expected to hatch within a few days into small larvae bearing feathery external gills behind the head — a larval feature shared across the genus — which are absorbed as the young mature.
Aquarium sources describe this species as rarely spawned in captivity, and it remains overwhelmingly a wild-caught fish in the trade rather than a farmed one — unlike the Senegal bichir, which is now bred commercially in quantity. Deliberate home breeding of Poll's bichir should be considered a long-shot project rather than a routine outcome.
In the aquarium
Poll's bichir is a fairly common presence in the bichir trade and, by aquarium accounts, a hardy and adaptable fish for a keeper prepared for its adult size and predatory habits. A minimum tank size of roughly 75 US gallons (around 74 US gal) is recommended for an adult, furnished with soft sand substrate and bogwood or rockwork caves to shelter in by day, reflecting its nocturnal, cover-seeking nature. It is generally peaceable with fish too large to eat but will treat anything smaller as prey, so tankmates need to be chosen with that firmly in mind.
As with every bichir, a secure, gap-free lid is essential — these fish are accomplished escape artists that will exploit the smallest opening — while still leaving room at the surface for the fish to breathe air. Its heavy ganoid armour makes it a tough, forgiving aquarium subject, and it will accept a varied meaty diet of bloodworm, earthworms and similar foods without fuss.
Conservation
Polypterus polli is assessed as Least Concern on the IUCN Red List. It is distributed across a substantial stretch of the lower and central Congo basin, including the Malebo Pool region shared by Kinshasa and Brazzaville, and no species-specific population threat is documented in the sources reviewed here.
As with many Congo basin fishes, broader pressures on the river system — from fishing, habitat disturbance and development along the heavily populated Pool Malebo shoreline — are worth watching even where a species is not currently considered threatened. The trade in this species still relies substantially on wild-caught fish rather than captive-bred stock, which makes sustainable collection practices in its native range relevant to its long-term outlook.