About Gymnocorymbus ternetzi (Boulenger, 1895)
The black tetra, scientifically named Gymnocorymbus ternetzi, has several common names including petticoat tetra, high-fin black skirt tetra, black skirt tetra, black widow tetra, and blackamoor. It is a species of freshwater ray-finned fish that belongs to Acestrorhamphidae, the family of American characins. This species is native to the Paraguay River basin, which includes the mainly Pantanal region of south-central Brazil, Paraguay, and northeast Argentina. Populations found in the upper Paraná and Paraíba do Sul Rivers are most likely introduced. While this species was formerly recorded from the Guapore River, that population is now classified as G. flaviolimai, a species described in 2015 that occurs across the Madeira River basin. Black tetra is a species commonly kept in aquariums. It can reach a maximum length of 7.5 cm (3.0 in). It has an approximately tetragonal body shape, with a greyish body color that fades from near-black at the tail to lighter towards the snout. Two distinct, black vertical bars are located just behind the gills. It can be easily told apart from all other species in its genus by a dense, evenly spread patch of dark chromatophores that covers the posterior half of its body; all other members of the genus lack this pigmentation. The black tetra, also called black widow tetra, is a shoaling species that feeds on small crustaceans, insects, and worms.
