Ann Marie Butler, age 13, of Denton, Tex., for her question:
HOW DOES AN ELECTRIC FISH GET ITS POWER?
There are a number of fishes that can produce electric current that they use as power to attack prey or to defend themselves. This electric power is obtained by means of special body organs or electric sensory cells.
Most of the electric fishes are found in the warm seas and rivers of the world. The most dangerous and the best known of all of them is the so called electric eel, which can be found in the fresh waters of the Guianas and Brazil.
The electric eel, properly called the Electrophorus electricus, is not actually an eel but is a relative of the catfishes and carps. It sometimes grows to a length of nine feet and is thicker than a man's thigh. Its normal length, however, is three feet.
This fish is black or dark gray in color. It has very primitive dorsal, or back, and caudal, or side, fins. Sometimes these fins are completely missing. The anal fin is on the underside of the eel and it extends the full length of the body.
The electric eel's electric organs are found in its tail, which makes up about four fifths of the total length of the fish. With a shock from this powerful tail, the eel is able to stun the animal that it uses for food.
The eel's tail can also be used to protect itself from its enemies. The size of the fish and its health determine the strength of the electric shock. And when both the head and the tail of the eel come in contact with the prey or enemy, the greatest amount of electric shock is sent out. The shock is strong enough then to stun a human being. The eel's power from the electric sensory cell can be temporarily worn out.
Indians of the Orinoco and Amazon rivers in South America use electric eels as food. As part of their routine for capturing the fishes, the Indians first drive horses into the water. The eels soon exhaust their power supply on the horses and are then helpless to defend themselves as the Indians enter the water and scoop them up.
The eel's electric impulse is usually between 200 and 300 volts.
The electric catfish of Africa is another common electric fish. It can be found in the Nile and other warm rivers of Africa. It is smaller than the electric eel, never growing larger than four feet.
The catfish's electric organ lies under its soft skin and covers most of its body.
Another electric fish is the electric ray. It is found in most of the warm oceans of the world. It ranges in size from one to five feet in length. The electric organs are found on each side of the body between the head and the gills. Electric rays can discharge a shock powerful enough to injure a man. Some of the large rays weigh as much as 200 pounds.
Electric skates are similar to electric rays in appearance but their electric organs are located in their tails. Several kinds of electric skates are found in the oceans around Japan.