Peters's elephant-nose fish (''Gnathonemus petersii'') is an African freshwater elephantfish in the genus ''

Gnathonemus ''Gnathonemus'' is a genus of elephantfish in the family Mormyridae. Species There are currently four recognized species in this genus: * '' Gnathonemus barbatus'' Poll 1967 (Angolan mormyrid) * '' Gnathonemus echidnorhynchus'' Pellegrin 192 ...

''. Other names in English include elephantnose fish, long-nosed elephant fish, and Ubangi mormyrid, after the

Ubangi River The Ubangi River (), also spelled Oubangui, is the largest right-bank tributary of the Congo River in the region of Central Africa. It begins at the confluence of the Mbomou (mean annual discharge 1,350 m3/s) and Uele Rivers (mean annual discharge ...

. The

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

name is probably for the German naturalist

Wilhelm Peters Wilhelm Karl Hartwich (or Hartwig) Peters (22 April 1815 in Koldenbüttel – 20 April 1883) was a German natural history, naturalist and explorer. He was assistant to the anatomist Johannes Peter Müller and later became curator of the Natural ...

. The fish uses electrolocation to find prey, and has the largest brain-to-body oxygen use ratio of all known vertebrates (around 0.6).Nilsson G (1996
"Brain and body oxygen requirements of Gnathonemus petersii, a fish with an exceptionally large brain"
''Journal of Experimental Biology'', 199(3): 603-607
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Description

Peters's elephantnose fish is native to the rivers of

West West or Occident is one of the four cardinal directions or points of the compass. It is the opposite direction from east and is the direction in which the Sunset, Sun sets on the Earth. Etymology The word "west" is a Germanic languages, German ...

and

Central Africa Central Africa is a subregion of the African continent comprising various countries according to different definitions. Angola, Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, the Republic of the Congo, ...

, in particular the lower

Niger River The Niger River ( ; ) is the main river of West Africa, extending about . Its drainage basin is in area. Its source is in the Guinea Highlands in south-eastern Guinea near the Sierra Leone border. It runs in a crescent shape through ...

basin, the Ogun River basin and the upper Chari River. It prefers muddy, slowly moving rivers and pools with cover such as submerged branches. The fish is a dark brown to black in colour, laterally compressed (averaging ), with a rear dorsal fin and anal fin of the same length. Its caudal or tail fin is forked. It has two stripes on its lower pendicular. Its most striking feature, as its names suggest, is a trunk-like protrusion on the head. This is not actually a nose, but a sensitive extension of the mouth, that it uses for

self-defense Self-defense (self-defence primarily in Commonwealth English) is a countermeasure that involves defending the health and well-being of oneself from harm. The use of the right of self-defense as a legal justification for the use of force in ...

communication Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inquir ...

navigation Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...

, and finding worms and insects to eat. This organ, called the Schnauzenorgan, is covered in

electroreceptors Electroreception and electrogenesis are the closely-related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes to stu ...

, as is much of the rest of its body. The elephantnose uses a weak

electric field An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field fo ...

, which it generates with specialized cells called electrocytes, which evolved from muscle cells, to find food, to navigate in dark or turbid waters, and to find a mate. Peters's elephantnose fish live to about 6–10 years.

Electrolocation

The elephant nose fish is weakly electric, meaning that it can detect moving prey and worms in the substrate by generating brief electric pulses with the

electric organ An electric organ, also known as electronic organ, is an electronic keyboard instrument which was derived from the harmonium, pipe organ and theatre organ. Originally designed to imitate their sound, or orchestral sounds, it has since developed ...

in its tail. The

around its body are sensitive enough to detect the different distortions of the electric field made by objects that conduct or resist electricity. The weak electric fields generated by this fish can be made audible by placing two electrodes in the fish tank, connected to an audio amplifier or a piezoelectric earbud.

In the aquarium

Peters's elephantnose fish is one of the most commonly available

freshwater elephantfish The Mormyridae, sometimes called "elephantfish" (more properly freshwater elephantfish), are a family of weakly electric freshwater fish in the order Osteoglossiformes native to Africa. It is by far the largest family in the order with around 20 ...

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 ...

stores in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

. In the aquarium it is timid, preferring a heavily planted environment with subdued lighting, and thrives in a tank of more than ; favourable additions to the fish's aquarium environment are a pipe or hollow log, alongside soft, sandy

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (locomotion), the surface over which an organism lo ...

, allowing the fish to sift through it with its delicate extended lip. The fish feeds on small worms (

bloodworm Blood worm or bloodworm is an ambiguous term and can refer to: * Larvae of a non-biting midge (family Chironomidae) containing hemoglobin * ''Glycera'' (annelid), a polychaete often used for fishing bait * Species of the Polychaeta subclass Scole ...

s being the most common) and aquatic invertebrates such as mosquito larvae, but will accept frozen or flake food. Elephantnose fish are typically kept in water of medium

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...

with a pH of 6.8 to 7.2 and a temperature of between . Elephantnose fish, though typically docile when kept in captivity, can be aggressive towards other species of fish, though some fare well in community aquarium environments. However, unless kept in an aquarium of over , elephantnose fish are aggressively territorial towards members of their own species. For this reason owners have been recommended not to keep more than one in captivity. The elephantnose fish has good low light vision. Its eyes use a combination of photonic crystals, parabolic mirrors and a clustered arrangement of rods and cones. The species has never been bred in captivity, meaning that all aquarium available specimens are wild-caught. This requires the owner to maintain specific water parameters if the fish is to thrive.

Notes

References

External links

* Peter Cain and Sapna Malwal, Landmark use and development of navigation behaviour in the weakly electric fish ''Gnathonemus petersii'' (Mormyridae; Teleostei), Journal of Experimental Biology, 205, 3915-3923 (2002)
Landmark use and development of navigation behaviour in the weakly electric fish Gnathonemus petersii (Mormyridae; Teleostei)

Photo
(BBC News)

{{Taxonbar , from=Q945393 Mormyridae Weakly electric fish Fish described in 1862 Taxa named by Albert Günther