Bichir

The bichir refers to species in the genus Polypterus (family Polypteridae), primitive freshwater fish native to rivers, swamps, and floodplains across tropical Africa, with Polypterus bichir as the type species. Bichirs represent one of the oldest surviving lineages of ray-finned fish, retaining ancestral features such as thick armored ganoid scales and a lung-like modified swim bladder that allows air breathing. Often called a living fossil, the group has changed relatively little over tens of millions of years. Bichirs are widely kept in the aquarium trade and remain common across much of their natural African range.

Bichirs are readily recognized by their primitive, eel-like build:

• Elongated, snake-like body covered in thick, bony ganoid scales
• A row of separate, spiny finlets running along the back instead of a single dorsal fin
• Tube-shaped external nostrils projecting from the snout
• Paired, lobed pectoral fins used for crawling along the bottom
• Mottled olive-brown to yellowish coloration Its armored scales and dorsal finlets distinguish it immediately from true eels, which lack both features entirely. The number of dorsal finlets and body pattern varies somewhat between the different Polypterus species within the genus.

Bichirs inhabit shallow freshwater rivers, swamps, floodplains, and oxygen-poor stagnant pools across tropical Africa, from West Africa through the Nile basin. They favor slow-moving or still water with dense vegetation and soft substrate, often in areas where dissolved oxygen levels are too low for many other fish. Their ability to breathe atmospheric air allows them to survive in stagnant floodplain pools and seasonal wetlands that would be uninhabitable for typical gill-dependent fish. Different Polypterus species occupy somewhat different habitat niches across the continent, from large rivers to small forest streams.

Bichirs are primarily nocturnal ambush predators, lying in wait to seize fish and invertebrates using a sudden lunge. Their modified swim bladder functions like a primitive lung, letting them gulp air at the surface and survive brief periods stranded out of water or in extremely low-oxygen conditions. They tend to burrow into soft substrate or hide among vegetation during the day, becoming more active after dark. Bichirs are largely solitary and territorial, using their lobed pectoral fins to crawl or prop themselves along the substrate.