Article
Article
Gymnotiformes
Article By:
Boschung, Herbert T. Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama.
Last reviewed:January 2020
DOI:https://doi.org/10.1036/1097-8542.803360
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An order of freshwater teleost fishes, comprising the Neotropical or South American knifefishes, in the superorder Ostariophysi, series Otophysi. Members of the order Gymnotiformes are characterized by a combination of the following features: Weberian ossicles (a series of small bones that form a chain connecting the swim bladder with the inner ear); an eel-like body, usually compressed, but sometimes rounded; absence of a dorsal fin; absence of a pelvic girdle and pelvic fins; a very long anal fin; a caudal fin that is absent or very small; and electric organs. The anal rays are articulated in a way that allows for circular motion; thus, undulation of the anal fin can move the gymnotiform fish forward or backward. The order Gymnotiformes comprises five families. See also: Electric organ (biology); Ostariophysi; Swim bladder; Teleostei
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