Description and Anatomy
– Electric rays have a rounded pectoral disc with two moderately large rounded-angular dorsal fins.
– They have a stout muscular tail with a well-developed caudal fin.
– The body is thick and flabby, with soft loose skin.
– They have a pair of kidney-shaped electric organs at the base of the pectoral fins.
– The snout is broad, large in the Narcinidae, but reduced in all other families.
Relationship to Humans and Historical Uses
– Electric rays have been used since ancient times for numbing pain during childbirth and operations.
– They were mentioned in Plato’s dialogue ‘Meno’ as a comparison to Socrates’ puzzling questions.
– Scribonius Largus, a Roman physician, recorded their use for treating headaches and gout.
– The electric organs of electric rays were studied by scientists like John Walsh, John Hunter, Luigi Galvani, and Alessandro Volta.
– Henry Cavendish built an artificial ray to mimic their behavior using fish-shaped Leyden jars.
– The use of electric rays in folklore as a magical creature with numbing abilities predates the discovery of electricity.
History of Research and Contributions to Science
– The electrogenic properties of electric rays have been known since antiquity.
– Royal Society papers in the 1770s by John Walsh and John Hunter discussed the electric organs of the torpedo ray.
– These papers influenced the thinking of Luigi Galvani and Alessandro Volta, founders of electrophysiology and electrochemistry.
– Henry Cavendish proposed that electric rays use electricity and built an artificial ray in 1773.
Bioelectricity
– Electric rays have specialized electric organs, with two large kidney-shaped organs on each side of their head.
– The electric organs are composed of hexagonal columns packed in a honeycomb formation.
– Each column consists of 500 to more than 1000 plaques of modified striated muscle.
– The electric organs in marine fish are connected as a parallel circuit, while freshwater rays have batteries arranged in series.
– Freshwater rays can transmit discharges of higher voltage compared to marine rays.
Systematics and Habitat
– There are about 60 species of electric rays grouped into 12 genera and two families.
– The torpedinids feed on large prey, stunning them with their electric organs and swallowing them whole.
– The narcinids specialize in small prey on or in the bottom substrate.
– Both groups use electricity for defense, but it is uncertain if narcinids use it for feeding.
– Electric rays are found in shallow coastal waters down to at least 1,000m (3,300ft) deep. Source: https://en.wikipedia.org/wiki/Electric_ray
The electric rays are a group of rays, flattened cartilaginous fish with enlarged pectoral fins, composing the order Torpediniformes /tɔːrˈpɛdɪnɪfɔːrmiːz/. They are known for being capable of producing an electric discharge, ranging from 8 to 220 volts, depending on species, used to stun prey and for defense. There are 69 species in four families.
| Electric rays Temporal range: | |
|---|---|
 | |
| Marbled electric ray (Torpedo marmorata) | |
 | |
| Lesser electric ray (Narcine bancroftii) | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Superorder: | Batoidea |
| Order: | Torpediniformes F. de Buen, 1926 |
| Families | |
Perhaps the best known members are those of the genus Torpedo. The torpedo undersea weapon is named after it. The name comes from the Latin torpere, 'to be stiffened or paralyzed', from the effect on someone who touches the fish.
