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.
Anatomy
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 97Â cm (38Â in).
Diet
Bichirs are nocturnal and feed on small vertebrates, crustaceans, and insects.
Air breathing
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.
Bichirs as aquarium specimens
Bichirs 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 and relatively inactive, preferring to lie on the bottom, and make good tankmates with other species large enough not to be prey. Bichirs in captivity have life expectancies up to 10 years.
Species
The two genera have 12 extant species:
Order Polypteriformes
- Family Polypteridae
- Genus †Bawitius Grandstaff et al. 2012
- †Bawitius bartheli (Schaal 1984) Grandstaff et al. 2012 - Late Cretaceous (Cenomanian) of Egypt
- Genus †Serenoichthys kemkemensis Dutheil 1999a
- †Serenoichthys kemkemensis Dutheil 1999a
- Genus Erpetoichthys J. A. Smith, 1865
- Erpetoichthys calabaricus J. A. Smith, 1865 (reedfish)
- Genus Polypterus Lacépède, 1803
- †Polypterus dageti Gayet & Meunier 1996
- †Polypterus faraou Otero et al., 2006 â€" late Miocene
- †Polypterus sudanensis Werner & Gayet 1997
- Retropinnis group
- Polypterus retropinnis Vaillant, 1899 (West African bichir)
- Bichir group
- Polypterus ansorgii Boulenger, 1910 (Guinean bichir)
- Polypterus bichir Lacépède, 1803 (Nile bichir)
- P. b. bichir Lacepède, 1803
- P. b. lapradei Steindachner, 1869
- P. b. ornatus Arambourg 1948
- Polypterus congicus Boulenger, 1898 (Congo bichir)
- Polypterus endlicheri Heckel, 1847 (saddled bichir)
- Weeksii group
- Polypterus mokelembembe Schliewen & Schäfer, 2006 (Mokèlé-mbèmbé bichir)
- Polypterus ornatipinnis Boulenger, 1902 (ornate bichir)
- Polypterus weeksii Boulenger, 1898 (mottled bichir)
- Senegalus group
- Polypterus delhezi Boulenger, 1899 (barred bichir)
- Polypterus polli J. P. Gosse, 1988
- Polypterus palmas Ayres, 1850 (shortfin bichir)
- P. p. buettikoferi Steindachner, 1891
- P. p. palmas Ayres, 1850
- Polypterus senegalus Cuvier, 1829 (gray bichir)
- P. s. meridionalis Poll, 1941 (most likely avariant of P. s. senegalus)
- P. s. senegalus Cuvier, 1829
- Polypterus teugelsi Britz, 2004 (Cross River bichir)
- Genus †Bawitius Grandstaff et al. 2012
References
External links
- FishBase entry for Polypteridae