Gymnarchus

Source: Wikipedia, the free encyclopedia.

Gymnarchus niloticus
Gymnarchus swims with its back straight, detecting prey by the way they distort the
electric field it generates
.

Least Concern  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Osteoglossiformes
Suborder: Notopteroidei
Family: Gymnarchidae
Bleeker, 1859
Genus: Gymnarchus
Cuvier, 1829
Species:
G. niloticus
Binomial name
Gymnarchus niloticus
Cuvier, 1829

Gymnarchus niloticus – commonly known as the aba, aba aba, frankfish, freshwater rat-tail, poisson-cheval, or African knifefish – is an

Senegal, and Gambia basins.[1][2]

Description and biology

Further information:
Electroreception

G. niloticus has a long and slender body, with no

anal fins. The dorsal fin is elongated, running along the back of the fish towards the blunt, finless tail, and is the main source of propulsion. It grows up to 1.6 m (5.2 ft) in length and 19 kg (42 lb) in weight.[3]

G. niloticus is nocturnal and has a poor vision. Instead, it navigates and hunts smaller fish using a weak electric field, as demonstrated by the zoologist Hans Lissmann in 1950, when he noticed that it could swim equally well forwards or backwards, clearly relying on a sense other than vision. This opened up research into electroreception and electrogenesis in fish.[4] Like the related elephantfish, which hunts the same way, it possesses an unusually large brain, which is believed to help it interpret the electrical signals.[3] It makes its tail negatively charged with respect to its head. This produces a symmetrical electric field around its body, provided it keeps its back straight; it does this by swimming using its fins. Nearby objects distort this field, and it can sense the distortion on its skin.[5]

G. niloticus females lay their eggs in floating nests up to 1 m (3.3 ft) across. The adults continue to guard the young after hatching.[3] The sperm cells lack a flagellum, moving like an amoeba instead.[6]

References

  1. ^
    doi:10.2305/IUCN.UK.2020-2.RLTS.T181688A134949091.en
    . Retrieved 23 December 2023.
  2. ^ Froese, Rainer; Pauly, Daniel (eds.) (2014). "Gymnarchus niloticus" in FishBase. April 2014 version.
  3. ^
    ISBN 0-12-547665-5
    .
  4. ^ Lissmann, Hans. "Continuous Electrical Signals from the Tail of a Fish, Gymnarchus Niloticus Cuv", in: Nature, 167, 4240 (1951), pp. 201–202.
  5. PMID 16391343
    .
  6. ISBN 978-1-4020-2996-7
    .

External links

Wikimedia Commons has media related to Gymnarchus niloticus.
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