The African brown knifefish (''Xenomystus nigri''), is the only species in the genus ''Xenomystus'' of the family

Notopteridae The family Notopteridae contains 10 species of osteoglossiform (bony-tongued) fishes, commonly known as featherbacks and knifefishes. These fishes live in freshwater or brackish environments in Africa and South and Southeast Asia. With the denot ...

. This fish is found in the

Chad Chad (; ar, تشاد , ; french: Tchad, ), officially the Republic of Chad, '; ) is a landlocked country at the crossroads of North and Central Africa. It is bordered by Libya to the north, Sudan to the east, the Central African Republic ...

Nile The Nile, , Bohairic , lg, Kiira , Nobiin language, Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered ...

, Congo, Ogowe and

Niger ) , official_languages = , languages_type = National languagesSierra Leone Sierra Leone,)]. officially the Republic of Sierra Leone, is a country on the southwest coast of West Africa. It is bordered by Liberia to the southeast and Guinea surrounds the northern half of the nation. Covering a total area of , Sierra ...

Liberia Liberia (), officially the Republic of Liberia, is a country on the West African coast. It is bordered by Sierra Leone to Liberia–Sierra Leone border, its northwest, Guinea to its north, Ivory Coast to its east, and the Atlantic Ocean ...

Togo Togo (), officially the Togolese Republic (french: République togolaise), is a country in West Africa. It is bordered by Ghana to the west, Benin to the east and Burkina Faso to the north. It extends south to the Gulf of Guinea, where its c ...

Benin Benin ( , ; french: Bénin , ff, Benen), officially the Republic of Benin (french: République du Bénin), and formerly Dahomey, is a country in West Africa. It is bordered by Togo to the west, Nigeria to the east, Burkina Faso to the north ...

and

Cameroon Cameroon (; french: Cameroun, ff, Kamerun), officially the Republic of Cameroon (french: République du Cameroun, links=no), is a country in west-central Africa. It is bordered by Nigeria to the west and north; Chad to the northeast; the C ...

Anatomy and appearance

This fish reaches 30 cm (12 in) in

standard length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...

. The body of these fish is unusual; it is ventrolaterally flattened and elongated, giving the appearance of a knife blade. The

caudal Caudal may refer to: Anatomy * Caudal (anatomical term) (from Latin ''cauda''; tail), used to describe how close something is to the trailing end of an organism * Caudal artery, the portion of the dorsal aorta of a vertebrate that passes into the ...

and

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

s are fused and run from beneath the gill opening to the pointed end of the body, creating a uniform, skirt-like fin. This appendage gives the animal superior control in the water, as it is able to propel itself forward and backward with a minimum of wasted energy. The

pelvic fins Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

are extremely reduced and are not used in locomotion. The

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

is absent. The

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

s of the African brown knifefish are lengthy and designed to give the animal precise control as it swims. They are often employed in a windmilling motion, in conjunction with the caudal/anal fin, as the fish retreats into its lair. The

scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number w ...

of the knifefish are extremely small, giving it a smooth appearance broken only by its fairly prominent

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

. Apart from its eyes, the lateral line is the knifefish's most important sensory apparatus. The African brown knifefish is

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

and uses the nerve-filled pits running down its body to navigate lightless waters. In addition, the eyes of this fish are large in relation to its body size. They provide the animal with excellent night vision. The mouth is large, and the fish also possesses a pair of short

barbels In fish anatomy and turtle anatomy, a barbel is a slender, whiskerlike sensory organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the zebrafish, the black dragonfish and some ...

used in hunting. The knifefish, when not hiding away, spends much of its time swimming with its head down and the barbels in close proximity to the substrate. Combined with its acute eyes, the barbels aid the fish in locating its food.

Ecology

This fish inhabits quiet water with vegetation. Females lay 150–200

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

of 2 mm (0.08 in) in diameter. This species can produce barking sounds. They come to the surface from time to time to swallow air. They feed on

worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete wor ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

s, and

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gastro ...

In the aquarium

This species is sometimes available as an

aquarium An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...

fish, and has been popular in the hobby for a long time. Because this fish is primarily nocturnal, it will retreat from brightness in the aquarium. When larger, these fish may prey upon smaller tankmates as these fish have relatively large mouths for their size. This fish does well when kept in small groups when young, although as it ages, it becomes somewhat aggressive towards those of its own kind.

References

* Innes, Dr William T. Exotic Aquarium Fishes, 19th edition, Innes Publishing Co. Philadelphia, 1956. {{DEFAULTSORT:knifefish, brown, African African brown knifefish Freshwater fish of Africa African brown knifefish African brown knifefish

Anatomy and appearance

Ecology

In the aquarium

See also

References