Definitions

bichir

bichir

[bich-er]
bichir, common name for African freshwater fishes as of the family Polypteridae, and particularly for those of the genus Polypterus. Bichirs are among the most primitive of the ray-finned fishes, or Actinopterygii, the dominant group of modern fishes. The long, narrow body of Polypterus is 2 to 3 ft (60-90 cm) long and is covered by thick, rhombic scales made of an enamellike substance called ganoine. Such scales were also present in the earliest ray-finned fishes, now extinct, and are quite different from those of other living fishes. The dorsal fin of the bichir is split into a row of small, saillike finlets that are erected when the animal is agitated. Like the sharks and the rays, it has a pair of spiracles. The bichir seems especially adapted to life in dry environments. Instead of the swim bladder of most ray-finned fishes, it has a pair of lungs, somewhat like those of the lungfishes, which enables it to survive out of water for several hours. It also resembles the lungfishes in having a pair of external gills when newly hatched. The bichir is a bottom-dwelling fish, found in the Nile and in the rivers of W Africa. When these rivers overflow in late summer, it moves out to spawn in the flood marshes. It is sometimes caught as a food fish. In addition to the ten species of Polypterus, the bichir family includes the reedfish, Erpetoichthys calabaricus, similar in character and distribution, but with a longer, more eellike form. Bichirs are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Polypteriformes, family Polypteridae.
The bichirs are a family, Polypteridae, of archaic-looking ray-finned fishes, the sole family in the order Polypteriformes.

Anatomy and appearance

They have thick bonelike ganoid scales and a series of 8-15 dorsal finlets instead of a single dorsal fin. Each of these finlets have a sharp spine. Their jaw structure more closely resembles that of the tetrapods than that of the teleost fishes. Bichirs have a number of other primitive characteristics. One of these such characteristics are fleshy pectoral fins similar to lobe-finned fishes. They also have spiracles. All species occur in freshwater habitats in Africa, mainly swampy, shallow floodplains and estuaries. They have rudimentary lungs, which allow them to obtain oxygen from the air when in poorly oxygenated waters, by swimming quickly to the surface and back to the bottom.

The maximum length among these species is about 90 cm, although most will not exceed much more than 30 cm.

Relationship to humans

Bichirs are popular subjects of public and large hobby aquaria. Though predatory, they are otherwise peaceful and relatively nonactive, preferring to lie on the bottom, and make good tankmates with other species that are large enough not to be prey. Some aquarists note that Loricariid catfish may attack bichirs and suck on their skin.

Species

There are eighteen extant species and subspecies in two genera:

Extinct species include:

References

External links

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