South American Knifefishes and Electric Eels: Gymnotiformes

Physical characteristics: Female glass knifefishes are about 8 inches (20 centimeters) long. Males are about 14 inches (36 centimeters) long. Their bodies are slender, having only pectoral fins (PECK-ter-uhl) fins, or the front pair, and a very long anal fin. Except for the head, the fish are clear. Three black stripes run lengthwise along the body. Glass knifefishes are weakly electric.

Geographic range: Glass knifefishes live in South America.

Glass knifefishes are weakly electric. Except for their heads, the fish are clear. (©Mark Smith/Photo Researchers, Inc. Reproduced by permission.)

Habitat: Glass knifefishes live near undercut banks and in old wood along rivers and streams; in the open-water areas of small creeks, lagoons, and marshes; and along rivers with dense plant life.

Diet: Glass knifefishes eat crustaceans and the larvae of water insects.

Behavior and reproduction: Glass knifefishes are social and are active at night. During the day they gather in large numbers in hiding places. They spawn during the rainy season. The dominant male spawns with a female at night, and she lays sticky eggs on floating plants. The eggs hatch on the third day after being laid.

Glass knifefishes and people: Glass knifefishes are studied by scientists.

Conservation status: Glass knifefishes are not threatened or endangered. ∎