Longtail Knifefish

Perception Channels: tactile ; chemical

None.

Sternopygus macrurus is commercially important in fisheries and aquariums. (Ortega and Vari 1986)

Sternopygus macrurus is a predator of small invertebrates. Its diet is mainly composed of aquatic insect larvae. (Planquette, Keith, and LeBail 1996)

Sternopygus macrurus occurs in many freshwater bodies in South America. It is known to inhabit the area from the Magdalena River to the Sao Francisco River and western Ecuador. It is also found in the Catatumbo River and the Amazon in Peru. (Ortega and Vari 1986)

Biogeographic Regions: neotropical (Native )

Sternopygus macrurus is most common in benthopelagic and freshwater bodies such as swamps, creeks, and rivers with lentic waters. The pH range for S. macrurus is 6.0 to 6.5 and the dH range is 4.0 to 15.0. (Ortega and Vari 1986)

Aquatic Biomes: benthic ; rivers and streams

Sternopygus macrurus is a knife-shaped fish. It has a slender body with a tapering tail. The maximum length of the Longtail Knifefish is 100.0 cm in total length. S. macrurus is an electric fish. From the larval stage on, an electric organ and electroreceptors are present. (Kirschbaum 1995)

Other Physical Features: bilateral symmetry

The male Sternopygus macrurus defends a territory. Just before or during the rainy season, the male will attract a female passing though his territory as a spawning partner. He attracts a female using electric signals from his electric organ. A single mating results in over 6000 eggs. (Hopkins 1972; Provenzano 1984; Kirschbaum 1995)

Cystidicoloides Infection 1. Parasitic infestations (protozoa, worms, etc.)

Spinitectus Infestation 9. Parasitic infestations (protozoa, worms, etc.)

Eggs of 3 mm diameter are deposited among plants. Larvae hatch after 4 days and start feeding after 11 days.

Analsoft rays: 195 - 300

Occurs in swamps, creeks, and river with lentic waters. Preys on small invertebrates, particularly the larvae of aquatic insects (Ref. 12225). Males persistently defend their territory and apparently make electric signals (by increased electric organ discharge (EOD) rates and interruptions thereof) to females passing by to draw in a spawning partner (Ref. 10605). Mature females' EODs are of higher frequencies than mature males (Ref. 10645).

Occurs in swamps, creeks, and river with lentic waters. Preys on small invertebrates, particularly the larvae of aquatic insects (Ref. 12225). Breeds before the start of the rainy season (Ref. 10645) or during the rainy season, with a fecundity count of 6473 eggs (Ref. 10643). Males persistently defend their territory and apparently make electric signals (by increased electric organ discharge (EOD) rates and interruptions thereof) to females passing by to draw in a spawning partner (Ref. 10605). Mature females' EODs are of higher frequencies than mature males (Ref. 10645). Plasma androgens modulate the EOD frequency during the breeding season (Ref. 10767). Embryos hatch on day 4; larvae begin to feed on day 11. The electric organ and electroreceptors are both present in the larva at the time of first exogenous feeding (Ref. 10605). Seems to reach sexual maturity at 1 year of age, based on breeding experiments (Ref. 10011).

fisheries: commercial; aquarium: commercial