Gymnotiformes
From Wikipedia, the free encyclopedia
| Gymnotiformes Fossil range: Late Jurassic - Recent[1] |
||||||||
|---|---|---|---|---|---|---|---|---|
 |
||||||||
| Scientific classification | ||||||||
|
||||||||
| Families | ||||||||
The Gymnotiformes is a lineage of ostariophysan teleost electric fishes. Common names found in the literature include the Neotropical electric fishes, South American electric fishes, or American knifefishes. They are primarily freshwater inhabitants and have organs adapted to the generation of electric fields.
Perhaps the best-known species is the electric eel (Electrophorus electricus) which uses powerful electric shocks (up to 600 V) for hunting and self-defense. Other species familiar in the aquarium trade are: the black ghost knifefish (Apteronotus albifrons), the glass knifefish (Eigenmannia virescens), and the banded knifefish Gymnotus carapo.
Contents |
[edit] Taxonomy
There are currently about 150 known species in 32 genera contained in 5 families, and at least 50 or so additional species are known and are yet to be formally described[2]. The actual number of species in the wild is unknown[3]. This group is thought to be the sister group to the Siluriformes[4] from which they diverged in the Cretacous Period (about 120 million yearrs ago).
The families are classified over suborders and superfamilies as below.[5]
Order Gymnotiformes
- Suborder Gymnotoidei
-
- Family Gymnotidae (banded knifefishes and electric eel)
-
- Suborder Sternopygoidei
- Superfamily Rhamphichthyoidea
- Family Rhamphichthyidae (sand knifefishes)
- Family Hypopomidae (bluntnose knifefishes)
- Superfamily Apteronotoidea
- Family Sternopygidae (glass knifefishes)
- Family Apteronotidae (ghost knifefishes)
- Superfamily Rhamphichthyoidea
[edit] Distribution and habitat
Gymnotiform fishes inhabit freshwater rivers and streams throughout the humid Neotropics, ranging from Guatemala to Northern Argentina. They are nocturnal fishes.
[edit] Evolution
Gymnotiformes are regarded as the among more derived members of Ostariophysi, a lineage of primary freshwater fishes. They arose in the western portion of Gondwana in what is now South America before the geological sepatation with Africa about 120 million years ago. The only known fossils are from the Miocene about 10 million years ago of Bolivia[6].
Gymnotiformes has no extant species in Africa. This may be because they did not spread into Africa before South America and Africa split, or it may be that they were outcompeted by mormyrids, which are similar in that they also use electrolocation.[2].
[edit] Physical characteristics
Gymnotiformes have a knife-shaped (culteriform), eel-like body that is either compressed or cylindrical. They lack pelvic fins or a dorsal fin. The anal fin is extremely long; this fin is undulated to allow the fish to move both forwards and backwards. The caudal fin is absent or, in the apteronotids, greatly reduced. The gill opening is restricted. The anal opening is under the head or the pectoral fins[7].
These fish possess electric organs that allow them to produce electricity. In most Gymnotiforms, the electric organs are derived from muscle cells. However, in adult apteronotids they are derived from nerve cells (spinal electromotor neurons). All gymnotiform species generate weak (<1 V) electric fields, using them for navigation and communication. The electric discharge is continuous, being generated day and night throughout the entire life of the individual. Certain aspects of the electric signal are unique to each species, especially a combination of the pulse waveform, duration and repetition rate {Crampton and Albert, 2006}.
[edit] See also
[edit] References
- Crampton, W.G.R. and J.S. Albert. 2006. Evolution of electric signal diversity in gymnotiform fishes. Pp. 641-725 in Communication in Fishes. F. Ladich, S.P. Collin, P. Moller & B.G Kapoor (eds.). Science Publishers Inc., Enfield, NH.
- ^ "Gymnotiformes". FishBase. Ed. Ranier Froese and Daniel Pauly. Apr 2007 version. N.p.: FishBase, 2007.
- ^ a b Albert, J.S., and W.G.R. Crampton. 2005. Electroreception and electrogenesis. Pp. 431-472 in The Physiology of Fishes, 3rd Edition. D.H. Evans and J.B. Claiborne (eds.). CRC Press.
- ^ Albert, J.S. and W.G.R. Crampton. 2005. Diversity and phylogeny of Neotropical electric fishes (Gymnotiformes). Pp. 360-409 in Electroreception. T.H. Bullock, C.D. Hopkins, A.N. Popper, and R.R. Fay (eds.). Springer Handbook of Auditory Research, Volume 21 (R.R. Fay and A. N. Popper, eds). Springer-Verlag, Berlin.
- ^ Fink and Fink, 1996
- ^ Nelson
- ^ Albert, J.S. and W.L. Fink. 2007. Phylogenetic relationships of fossil Neotropical electric fishes (Osteichthyes: Gymnotiformes) from the Upper Miocene of Bolivia. Journal Vertebrate Paleontology 27(1):17-25.
- ^ Albert, J.S. 2001. Species diversity and phylogenetic systematics of American knifefishes (Gymnotiformes, Teleostei). Misc. Publ. Mus. Zool. University of Michigan, 190:1-127.
[edit] External links
|
|||||||||||
