The family Torpedinidae contains 22 species of electric rays or torpedoes, flat chondrichthyes that Electric fish as a defense and feeding mechanism. They are slow-moving bottom-dwellers.
The largest species is the Atlantic torpedo, Tetronarce nobiliana, which can grow to a weight of and deliver a 220-volt electric shock. Electric rays have patches of modified muscle cells called electroplaques that make up an electric organ. These generate an electric gradient, similar to the normal electric potential across most cell membranes, but amplified greatly by its concentration into a very small area. The electricity can be stored in the tissues, which act as a battery. The shock can be discharged in pulses. A ray can emit a shock into the body of a prey animal to stun it and make it easier to capture and eat, or into the body of a predator. Tissue from electric rays is often used in neuroscience research because of its unique properties.
Torpedo rays are flat like other rays, disc-shaped, with caudal fins that vary in length. Their mouths and gill slits are located on their undersides. Males have near the base of the tail. Females are Ovoviviparity, meaning they form eggs but do not lay them. The young emerge from the eggs within the body of the female, and she gives live birth. The young are called pups.
The naval weapon known as the torpedo was named after this genus, whose own name has the same Latin origin as the English word torpid, meaning "sluggish" or "lethargic", presumably the sensations one would feel after experiencing the ray's electric shock.
Species
There are 22 species in 2 genera:
[Carvalho, M.R. de. (2015): Torpedinidae. In : Heemstra, P.C., Heemstra, E. & Ebert, D.A. (Eds.), Coastal Fishes of the Western Indian Ocean. Vol. 1. South African Institute for Aquatic Biodiversity, Grahamstown, South Africa. In press.]
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Genus Tetronarce T. N. Gill, 1862
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Tetronarce californica Ayres, 1855 (Pacific electric ray)
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Tetronarce cowleyi Ebert, D. L. Haas & M. R. de Carvalho, 2015 (Cowley's torpedo ray)
[Ebert, D.A., Haas, D.L. & de Carvalho, M.R. (2015): Tetronarce cowleyi, sp. nov., a new species of electric ray from southern Africa (Chondrichthyes: Torpediniformes: Torpedinidae). Zootaxa, 3936 (2): 237–250.]
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Tetronarce fairchildi F. W. Hutton, 1872 (New Zealand torpedo)
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Tetronarce formosa D. L. Haas & Ebert, 2006 (Taiwan torpedo)
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Tetronarce macneilli Whitley, 1932 (Shorttail torpedo)
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Atlantic torpedo Bonaparte, 1835 (Atlantic torpedo)
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Tetronarce puelcha Fernando Lahille, 1926 (Argentine torpedo)
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Tetronarce tokionis Shigeho Tanaka, 1908 (Trapezoid torpedo)
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Chilean torpedo F. de Buen, 1959 (Chilean torpedo)
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Genus Torpedo Forsskål, 1775
[Welter-Schultes, F.W., V. Feuerstein (2008) Nomenclatural notes on Torpedo (Chondrichthyes: Torpedinidae) and some other early established fish taxa (Actinopterygii: Molidae, Eleginopidae and Citharinidae). Species, Phylogeny and Evolution 1(3):141-145.]
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Torpedo adenensis M. R. de Carvalho, Stehmann & Manilo, 2002 (Aden Gulf torpedo)
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Torpedo alexandrinsis Mazhar, 1987 (Alexandrine torpedo)
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Florida torpedo Bullis, 1962 (Florida torpedo)
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Torpedo bauchotae Jean Cadenat, Capapé & Desoutter, 1978 (Rosette torpedo)
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Torpedo fuscomaculata Wilhelm Peters, 1855 (Black-spotted torpedo)
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Torpedo mackayana Metzelaar, 1919 (Ringed torpedo)
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Torpedo marmorata Antoine Risso, 1810 (Marbled electric ray)
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Torpedo microdiscus Parin & Kotlyar, 1985 (Smalldisk torpedo)
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Leopard torpedo Olfers, 1831 (Leopard torpedo)
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Torpedo semipelagica Parin & Kotlyar, 1985 (Semipelagic torpedo)
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Gulf torpedo Olfers, 1831 (Variable torpedo or Gulf torpedo)
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Torpedo suessii Steindachner, 1898
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Common torpedo (Carl Linnaeus, 1758) (Common torpedo)
