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Torpediniformes - Accessscience from Mcgraw-Hill Education Page 1 of 3 Torpediniformes - AccessScience from McGraw-Hill Education Page 1 of 3 Torpediniformes Article by: Boschung, Herbert Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama. Publication year: 2014 DOI: http://dx.doi.org/10.1036/1097-8542.803220 (http://dx.doi.org/10.1036/1097-8542.803220) Content • Torpedinidae (torpedo electric rays) • Narcinidae (electric rays or numbfishes) • Bibliography • Additional Readings An order of batoid fishes occurring in the subclass Elasmobranchii and known as the torpedo electric rays and numbfishes. Typical members of Torpediniformes are identifiable by their flat, pancakelike body sector (disc); relatively robust tail sector; smooth skin; small or obsolete eyes; 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 best be seen 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 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 (6 ft) and a weight of 44 kg (100 lb). Torpediniforms occur in intertidal waters to deep waters [1070 m or 3510 ft in the case of blind species (Benthobatis)] in temperate to tropical zones of all oceans. The order comprises two families: Torpedinidae and Narcinidae. Torpedinidae (torpedo electric rays) The disc is truncate anteriorly or emarginate; the rostrum is reduced; the jaws are extremely slender and lack labial cartilages. There are two genera, Torpedo (21 species) and Hypnos (1 species). Torpedo differs from Hypnos in having well-developed dorsal and caudal fins vs. very small dorsal and caudal fins, and in having worldwide distribution vs. distribution limited to off Australia. http://www.accessscience.com/content/torpediniformes/803220 7/21/2015 Torpediniformes - AccessScience from McGraw-Hill Education Page 2 of 3 Narcinidae (electric rays or numbfishes) The disc is rounded anteriorly; a rostrum is present; the jaws are stout and the labial cartilages strong. There are nine genera and 37 species in two subfamilies, Narcininae (numbfishes) with four genera and 26 species and Narkinae (sleeper rays) with five genera and 11 species. Narcininae (see illustration) differs from Narkinae in having long, strongly protractile jaws vs. short, weakly protractile jaws; a deep groove around the mouth and lips vs. shallow grooves; a broad rostrum vs. narrow; usually two dorsal fins vs. usually one dorsal fin; and species occur in Atlantic, Indian, and Pacific oceans vs. limited to Indo-West Pacific. See also: Batoidea (/content/batoidea/075000); Elasmobranchii (/content/elasmobranchii/214800); Electric organ (biology) (/content/electric-organ-biology/216500); Myliobatiformes (/content/myliobatiformes/803110); Pristiformes (/content/pristiformes/803450); Rajiformes (/content/rajiformes/802690) Example of a Narcinidae species. (Courtesy of J. S. Nelson, Fishes of the World, 4th ed., Wiley, 2006) Herbert Boschung Bibliography H. B. Bigelow and W. C. Schroeder, in J. Tee-Van et al. (eds.), Fishes of the Western North Atlantic, Sears Found. Mar. Res. Mem. 1, pt. 2, 1954 L. J. V. Compagno, Checklist of Chondrichthyes, pp. 503–547 in W. C. Hamlett (ed.), Reproductive Biology and Phylogeny of Chondrichthyes: Sharks, Batoids and Chimaeras, Science Publishers, Enfield, NH, 2005 J. D. McEachran and N. Aschliman, Phylogeny of Batoidea, pp. 79–113 in J. C. Carrier, J. A. Musick, and M. R. Heithaus (eds.), Biology of Sharks and Their Relatives, CRC Press, Boca Raton, FL, 2004 J. D. McEachran and M. R. de Carvalho, Batoid fishes, pp. 507–589 in K. E. Carpenter (ed.), The Living Marine Resources of the Western Central Atlantic: FAO Species Identification Guide for Fishery Purposes, vol. 1, FAO, Rome, 2002 J. D. McEachran, K. A. Dunn, and T. Miyake, Interrelationships of the batoid fishes (Chondrichthyes: Batoidea), pp. 63–84 in M. L. J. Stiassny, L. R. Parenti, and G. D. Johnson (eds.), Interrelationships of Fishes, Academic Press, San Diego, 1996 http://www.accessscience.com/content/torpediniformes/803220 7/21/2015 Torpediniformes - AccessScience from McGraw-Hill Education Page 3 of 3 J. S. Nelson, Fishes of the World, 4th ed., Wiley, New York, 2006 Additional Readings J. C. Carrier, J. A. Musick, and M. R. Heithaus (eds.), Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation, CRC Press, Boca Raton, FL, 2010 K. Jensen, P. Nikolov, and J. N. Caira, A new genus and two new species of Anteroporidae (Cestoda, Lecanicephalidea) from the darkspotted numbfish, Narcine maculata (Torpediniformes, Narcinidae), off Malaysian Borneo, Folia Parasit., 58(2):95–107, 2011 ReefQuest Centre for Shark Research (http://www.elasmo- research.org/education/shark_profiles/torpediniformes.htm) http://www.accessscience.com/content/torpediniformes/803220 7/21/2015 .
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