Boschung, Herbert T. Formerly, Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama.
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- Torpedinidae (torpedo electric rays)
- Narcinidae (electric rays or numbfishes)
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An order of batoid fishes occurring in the subclass Elasmobranchii and known as the torpedo electric rays and numbfishes. Typical members of the order Torpediniformes are identifiable by a flat, pancakelike body sector (disc); a relatively robust tail sector; smooth skin; small or obsolete eyes; a distinct caudal fin; and ovoviviparous development (that is, producing eggs that develop internally and hatch before or soon after extrusion). Of special interest is a pair of enlarged electric organs located on the disc lateral to the gill slits. These kidney-shaped organs can be seen best from the ventral side, although the columnar structures that compose them occupy the thickness of the disc. These electric organs, which may constitute 17% of the total body weight, deliver shocks up to 220 volts. The voltage depends on the species, its size, and its physical condition. The electric organs are thought to be used primarily for feeding and defense. Electric rays are poor swimmers, depending primarily on the tail because the disc is rather inflexible and of little use in locomotion, although it is flexible enough for capturing prey. They spend most of their time partially buried in sand or mud and feed on a variety of invertebrates, including crustaceans, mollusks, and worms, as well as small fishes. Members of the genus Torpedo are reported to reach a length of 1.8 m (5.9 ft) and a weight of 44 kg (97 lb). Torpediniforms occur in intertidal waters to deep waters [1070 m (3510 ft) in the case of blind species (Benthobatis)] in temperate to tropical zones of all oceans. See also: Batoidea; Chondrichthyes; Elasmobranchii; Electric organ (biology)
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