The family Torpedinidae contains 23 species of electric rays or torpedoes, flat cartilaginous fishes that produce electricity as a defense and feeding mechanism. They are slow-moving bottom-dwellers.
The largest species is the Atlantic torpedo, Torpedo nobiliana, which can grow to a weight of 90 kilograms 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 neurobiological 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 claspers near the base of the tail. Females are ovoviviparous, 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.
There are 23 species in two genera:
- Genus Hypnos
- Genus Torpedo
- Torpedo adenensis Carvalho, Stehmann & Manilo, 2002.
- Alexandrine torpedo, Torpedo alexandrinsis Mazhar, 1987.
- Florida torpedo, Torpedo andersoni Bullis, 1962.
- Rosette torpedo, Torpedo bauchotae Cadenat, Capape & Desoutter, 1978.
- Pacific electric ray, Torpedo californica Ayres, 1855.
- New Zealand torpedo, Torpedo fairchildi Hutton, 1872.
- Torpedo formosa Haas & Ebert, 2006.
- Black-spotted torpedo, Torpedo fuscomaculata Peters, 1855.
- Ringed torpedo, Torpedo mackayana Metzelaar, 1919.
- Shorttail torpedo, Torpedo macneilli (Whitley, 1932).
- Spotted torpedo, Torpedo marmorata Risso, 1810.
- Smalldisk torpedo, Torpedo microdiscus Parin & Kotlyar, 1985.
- Atlantic torpedo, Torpedo nobiliana Bonaparte, 1835.
- Panther electric ray, Torpedo panthera Olfers, 1831.
- Peruvian torpedo, Torpedo peruana Chirichigno F., 1963.
- Argentine torpedo, Torpedo puelcha Lahille, 1926.
- Semipelagic torpedo, Torpedo semipelagica Parin & Kotlyar, 1985.
- Marbled electric ray, Torpedo sinuspersici Olfers, 1831.
- Torpedo suessii Steindachner, 1898.
- Trapezoid torpedo, Torpedo tokionis (Tanaka, 1908).
- Common torpedo, Torpedo torpedo (Linnaeus, 1758).
- Torpedo, Torpedo tremens de Buen, 1959.