Torpedo

Collier's New Encyclopedia (1921)

in ichthyology, the type genus of Torpedinidæ, with the charac ters of the family. There are six species distributed over the Atlantic and Indian oceans; three of these occur in the Mediterranean, and two, T. marmorata and T. hebetans, are sometimes found on the British coast. The electric organs consist of many perpendicular prisms, mostly hexagonal, the whole forming a kidney-shaped mass. Each column in the living fish appears like a clear trembling jelly. Hunter counted 470 of these columns in a specimen of T. marmorata, and says that the partitions between them are full of arteries, which bring the blood direct from the gills. These organs convert nervous energy into electricity. Each organ receives one branch of the trigeminal and four branches of the vagus, the former and the three anterior branches of the latter being each as thick as the spinal cord. The fish gives the electric shock voluntarily, to stun or kill its prey or in self-defense; but to receive the shock the object must complete the circuit by communicating with the fish at two distinct points, either directly or through the medium of some conducting body. The force of the discharge varies with the size and vigor of the fish; large and healthy specimens can inflict severe shocks sufficient to disable a man. The electric currents generated in these fish possess all the other known powers of electricity; they render the needle magnetic, decompose chemical compounds, and emit sparks. Also the common name of any individual of the genus. In southern European waters the best known species is T. marmorata. It is dark brown in color, lighter round the eyes. Specimens have been taken weighing 100 pounds, but they usually average about half that weight, with the disk about 30 inches broad. T. hebetans, more rarely met with, is dark chocolate-brown above, white beneath. They are also called cramp fish and numb fish. A well-known American species is T. oc cidentalis.