Bichirs: Polypteriformes

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BICHIRS: Polypteriformes

BICHIR (Polypterus ornatipinnis): SPECIES ACCOUNT

PHYSICAL CHARACTERISTICS

Bichirs (bi-CHURS) have a slender body that is 16–47 inches (40–120 centimeters) long. The dorsal (DOOR-suhl) fin, the one that runs along the top, is divided into a series of small spiny fins, called finlets. Bichirs have a tubular pair of nostrils that extends in front of the mouth, and they have many small, sharp teeth. These fishes have a dense covering of shiny, diamond-shaped scales arranged in diagonals. On the inside, bichirs have paired swim bladders that function as air-breathing organs. This feature is unusual, because fishes usually use the swim bladder to control their position in the water. The right swim bladder is larger than the left one. Bichirs are olive brown to dark brown on the top and sides and over the head but are creamy white on the bottom. Some have dark or clear spots and blotches and irregular stripes, but others are a solid color. The heads of most bichirs are spotted.


GEOGRAPHIC RANGE

Bichirs live in western and central tropical Africa. Some live in the Nile River. Bichirs do not live in rivers that drain into the Indian Ocean.

HABITAT

Bichirs live in fast-moving and slow-moving rivers, floodplains, swamps, lakes, and pools. Because they are able to breathe air, bichirs can live in stagnant, or still, stale water.

DIET

Bichirs feed mainly on invertebrates (in-VER-teh-brehts), or animals that lack a backbone. They eat insect larvae (LAR-vee), that is, insects in the early stage of development; snails; earthworms; and freshwater crustaceans (krus-TAY-shuns), or animals that live in water and have a soft, segmented body covered by a hard shell. They also eat fishes and amphibians (am-FIB-ee-uns), animals that live part of their lives on land and part in water. Bichirs are primarily nocturnal (nahk-TER-nuhl) predators (PREH-duh-ters), meaning that they are active at night and hunt and kill other animals for their food.


BEHAVIOR AND REPRODUCTION

Not much is known about bichirs. They are reported to "walk" over land for small distances to feed on insects, because they are able to absorb oxygen directly from the air for at least a few hours. In aquariums the behavior of bichirs varies from remaining motionless on the bottom for short periods to swimming about vigorously. Their pectoral (PECK-ter-uhl) fins, or front pair, function as paddles.

Male bichirs use their anal (AY-nuhl) and caudal (KAW-duhl) fins to surround a female's genital (JEN-ih-tuhl), or reproductive, opening, making a pouch that receives the eggs from the female. The anal fin is the one that runs along the bottom of the body, and the caudal fin is the one at the end of the body. Fertilization (FUR-teh-lih-zay-shun), the joining of egg and sperm to start development, occurs in the pouch made with the fins. The male releases the eggs by shaking his anal fin, and the eggs quickly attach to plants. Bichirs do not care for their eggs or their young.


BICHIRS AND PEOPLE

Bichirs are used in the ornamental fish business. Large bichirs are used for food in West Africa.


CONSERVATION STATUS

Bichirs are not threatened or endangered.

BICHIR (Polypterus ornatipinnis): SPECIES ACCOUNT

Physical characteristics: The maximum length of bichirs is 24 inches (60 centimeters). The body is protected by an armor of large, diamond-shaped bony scales. These fishes are long and thin and have nine or ten small dorsal finlets. The pelvic fins are near the tail. Bichirs have a white belly with dark spots on the head, sides, and top and have parallel bands on the fins.


Geographic range: Bichirs live in central and eastern Africa in the Congo Basin and Lake Tanganyika.


Habitat: Bichirs live in lakes, rivers, floodplains, and swamps, including waters with low oxygen content.

Diet: Bichirs feed mostly at night and seek prey such as other fishes, frogs, insects, and crustaceans.


Behavior and reproduction: Bichirs often sit motionless on the bottom, resting on their pectoral fins so that the head and front of the body are slightly elevated. They gulp air from the surface in stagnant water. During courtship, bichirs make energetic twisting, turning, and darting movements. The male surrounds the female's genital opening with his anal and caudal fins, fertilizes the eggs, and then scatters them by thrashing his tail.


Bichirs and people: Bichirs are a food fish and are captured for the aquarium business.


Conservation status: Bichirs are not threatened or endangered. ∎

FOR MORE INFORMATION

Books:

Berra, Tim M. Freshwater Fish Distribution. San Diego, CA: Academic Press, 2001.

Ricciuti, Edward R. Fish. Woodbridge, CT: Blackbirch, 1993.


Web sites:

Caldas, Eduardo Pereira. "Bichir (Polypterus ornatipinnis)." WhoZoo. http://www.whozoo.org/Anlife99/eduardo/Bichir4.htm (accessed on August 29, 2004).

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Bichirs: Polypteriformes

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