The family Torpedinidae contains 22 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, Tetronarce 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 i