Polypteriformes
| Bichirs Temporal range: Cretaceous–Recent |
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|---|---|
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| Polypterus bichir | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Subclass: | Cladistia |
| Order: |
Polypteriformes Bleeker, 1859 |
| Family: | Polypteridae |
| Genera | |
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Erpetoichthys |
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Erpetoichthys
Polypterus
See text for species.
The bichirs and reedfish (also called ropefish) comprise the Polypteridae, a family of archaic-looking ray-finned fishes and the sole family in the order Polypteriformes.
All species occur in freshwater habitats in tropical Africa and the Nile River system, mainly swampy, shallow floodplains and estuaries.
Bichirs are considered the sister group to all other extant ray-finned fishes.
Bichirs 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 (double-edged) 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 (ganoid) 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 used to exhale air, two gular plates, and paired ventral lungs (the left lung shorter than the right). Four pairs of gill arches are present.
Bichirs have a maximum body length of 97 cm (38 in).
Bichirs are nocturnal and feed on small vertebrates, crustaceans, and insects.
Bichirs possess paired lungs which connect to the esophagus via a glottis. They are obligate air-breathers, requiring access to surface air to breathe in poorly oxygenated water. 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 (artery from the fourth gill arch), and oxygenated blood leaves the lungs in pulmonary veins. Unlike most lungfish and tetrapods, their lungs are smooth sacs instead of alveolated tissue. Bichirs are unique in that they breathe using a recoil aspiration.
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Wikipedia