Bichirs and the reedfish comprise Polypteridae, a family of archaic-looking ray-finned fishes and the only family in the orderPolypteriformes. All species occur in freshwater habitats in tropical Africa and the NileRiver system, mainly swampy, shallow floodplains and estuaries. Polypterids are considered the sister group to all other extant ray-finned fishes.
Anatomy
Polypterids are elongated fish with a unique series of dorsal finlets which vary in number from seven to 18, instead of a single dorsal fin. Each of the dorsal finlets has bifid tips, and are the only fins with spines; the rest of the fins are composed of soft rays. The body is covered in thick, bonelike, and rhombic scales. Their jaw structure more closely resembles that of the tetrapods than that of the teleost fishes. Bichirs have a number of other primitive characteristics, including fleshy pectoral fins superficially similar to those of lobe-finned fishes. They also have a pair of slit-like spiracles on the top of their heads that are used to breathe air, two gular plates, and paired ventral lungs. Four pairs of gill arches are present. Polypterids have a maximum body length ranging from to over depending on specific species and morphology.
Diet
Polypterids are nocturnal and feed on small vertebrates, crustaceans, and insects.
Air breathing
Polypterids possess paired lungs which connect to the esophagus via a glottis. They are facultative air-breathers, accessing surface air to breathe when the water they inhabit is poorly oxygenated. Their lungs are highly vascularized to facilitate gas exchange. Deoxygenated arterial blood is brought to the lungs by paired pulmonary arteries, which branch from the fourth efferent branchial arteries, and oxygenated blood leaves the lungs in pulmonary veins. Unlike most lungfish and tetrapods, their lungs are smooth sacs instead of alveolated tissue. Polypterids are unique in that they breathe using recoil aspiration. Polypterids appear to prefer breathing air via their spiracles when undisturbed or in extremely shallow waters where they are unable to incline their body enough to breathe air through their mouth.
Polypterids as aquarium specimens
Polypterids are popular subjects of public and large hobby aquaria. They are sometimes called dragon bichir or dragon fin in pet shops for a more appealing name due to their dragon-like appearance. Though predatory, they are otherwise peaceful, preferring to lie on the bottom, and make good tankmates with other species large enough to not be prey. Some aquarists note that catfish attack polypterids. Polypterids in captivity have life expectancies up to 10 years.
Species
The two genera have 12 extant species: Order Polypteriformes Suborder Polypterioidei Clade Salamandrophysida
