Green knife fish
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Green knife fish in the Berlin Aquarium . |
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| Eigenmannia virescens | ||||||||||||
| ( Valenciennes , 1836) |
The green knife fish ( Eigenmannia virescens ) is a freshwater fish from the order of the New World knife fish (Gymnotiformes). It occurs in South America east of the Andes from the Orinoco to the Río de la Plata and in the Río Magdalena west of the Andes . The genus was named after the American ichthyologist couple Carl H. Eigenmann and Rosa Smith Eigenmann , the specific epithet virescens means light green.
features
Green knife fish have an elongated, laterally strongly flattened body that ends in a long, whip-like tail. A caudal fin is missing, as are the dorsal fin and pelvic fins. Males become 45 cm long, females remain much smaller at 20 cm. The mouth is covered with a row of teeth. The long anal fin , which extends almost the entire length of the body, is the main driving organ of the fish. It enables them to swim both forwards and backwards through undulating movements and is supported by 215 to 255 fin rays. When swimming backwards, the highly flexible tail serves as a tactile organ. This will also find gaps and holes in which the fish can hide. The pectoral fins are supported by a hard fin ray and 17 to 21 soft rays. The green knife fish is translucent flesh-colored, head and chest are yellowish to yellow-red. In incident light it shimmers greenish to bluish. Many animals have blue iridescent to gray longitudinal stripes. Young green knifefish can also have irregular horizontal stripes. The fish have a weak electrical organ. Experiments showed that it is used, among other things, to differentiate between the sexes.
Way of life
Green knifefish occur in weed, slow-flowing to stagnant waters with a bottom covered with rotting plant material and prefer greater water depths. They live in simply structured social associations and are nocturnal. Only the dominant male mates in a group. Females lay up to 900 eggs, which are 1.5 mm in diameter and are attached to floating plants. At a water temperature of 27 ° C, the fry hatch after three days.
literature
- Günther Sterba : The world's freshwater fish. 2nd Edition. Urania-Verlag, Leipzig et al. 1990, ISBN 3-332-00109-4 .
- Günther Sterba (Ed.), Gert Brückner: Encyclopedia of Aquaristics and Special Ichthyology. Neumann-Neudamm, Melsungen u. a. 1978, ISBN 3-7888-0252-9 .
Web links
- Green Knife Fish on Fishbase.org (English)