Swamp and Spiny Eels: Synbranchiformes

Physical characteristics: Marbled swamp eels grow to about 59 inches (150 centimeters). They have a long cylindrical body, no pectoral or pelvic fins, and very small dorsal and anal fins. The pectoral (PECK-ter-uhl) fins, the front pair, correspond to the front legs of four-footed animals.

Geographic range: Marbled swamp eels live in North and South America from Mexico to central Argentina.

Marbled swamp eels are active at night, usually at the edge of the water. (Sullivan & Rogers. Bruce Coleman, Inc. Reproduced by permission.)

Habitat: Marbled swamp eels live in clear or murky freshwater and in water with a low salt content in a variety of habitats, including streams, canals, ponds, and rice fields.

Diet: Marbled swamp eels eat fish and invertebrates and are considered aggressive predators (PREH-duh-ters), or animals that hunt and kill other animals for food.

Behavior and reproduction: Marbled swamp eels are active at night, usually at the edge of the water. They can travel over land for long distances. They also burrow, especially during the dry season. During the time in the burrow the metabolism slows, but the fish still may flee if disturbed. After the first rains, marbled swamp eels return to larger bodies of water. Many marbled swamp eels function first as a female and then as a male. Others remain young females. Marbled swamp eels use external fertilization (FUR-teh-lih-zay-shun), meaning egg and sperm unite outside the body.

Marbled swamp eels and people: Marbled swamp eels sometimes appear in public aquariums, although they do not make a good exhibit because of their burrowing behavior.

Conservation status: Marbled swamp eels are not threatened or endangered. ∎