Bony Tongues and Relatives: Osteoglossiformes

Physical characteristics: Freshwater butterflyfishes (also called but-terflyfishes) are called that because their large pectoral (PECK-ter-uhl)fins, the front set of paired fins, look like the wings of a butterfly. The pelvic fins, the rear set of paired fins, have long rays that are not covered with skin. The fanlike tail fin is quite large. Freshwater butterfly-fishes reach a length of 3.9 inches (10 centimeters). The upper part of the body is olive green, and the bottom is silvery yellow with touches of red. Freshwater butterflyfishes are not related to the butterflyfishes that live in coral reefs.

Geographic range: Freshwater butterflyfishes live in central Africa.

Freshwater butterflyfishes got their name because their large pectoral fins look like the wings of a butterfly. (Illustration by Bruce Worden. Reproduced by permission.)

Habitat: Freshwater butterflyfishes live near the surface in stagnant water.

Diet: Freshwater butterflyfishes eat crustaceans, insects, and small fishes.

Behavior and reproduction: Freshwater butterflyfishes can jump out of the water. They do this for feeding or to escape predators (PREH-duhters). They have been seen gliding 13 to 16 feet (4 to 5 meters), but scientists want more proof of this behavior, because they do not believe the muscles that support the pectoral fins are large enough for lengthy flight. These fishes can use the swim bladder, an internal sac that fishes use to control their position in the water, to breathe air.

Freshwater butterflyfishes have a long spawning season. Each night they lay between eighty and two hundred buoyant eggs, or eggs that can float on the water. The embryos hatch after thirty-six hours. These fishes grow quickly, reaching their adult length within one year.

Freshwater butterflyfishes and people: Freshwater butterflyfishes are used in home aquariums.

Conservation status: Freshwater butterflyfishes are not threatened or endangered. ∎