Characterized by a robust, scaleless, and elongated body, this siluriform fish exhibits a smooth skin covered in protective mucus. Its coloration is typically silvery-gray or bluish-white on the dorsal region, transitioning to an immaculate white on the abdominal surface. A key diagnostic feature is the presence of three pairs of highly developed barbels, with the maxillary pair being remarkably long, frequently extending past the origin of the caudal fin. The head is broad and dorsoventrally flattened, hosting medium-sized eyes in a late-superior position. The dorsal and pectoral fins are armed with formidable, serrated, and sharp spines, which are connected to venom glands capable of inflicting painful wounds upon potential predators or handlers. Adult individuals commonly attain standard lengths of 30 to 50 centimeters, with maximum recorded lengths reaching up to 60 centimeters and weights surpassing 2 to 3 kilograms in fully mature specimens.

Geographical distribution: Endemic to the vast La Plata River basin in southern South America. Its geographic range encompasses major river systems within Argentina, Brazil, Paraguay, and Uruguay. It is a particularly dominant species throughout the Paraná River, Paraguay River, and Uruguay River, as well as within the estuarine waters of the Río de la Plata, where its physiological tolerance allows it to adapt to fluctuating oligohaline and mixohaline conditions.

Habitat: Inhabits primarily lotic freshwater environments, demonstrating a clear preference for the main channels of large rivers, deep river bends, and slow-moving secondary channels. It is highly associated with benthic zones characterized by muddy, sandy, or clayey substrates, where turbidity is high and light penetration is minimal. It also colonizes floodplain lakes and artificial reservoirs, displaying high ecological plasticity to tolerate fluctuations in water temperature, dissolved oxygen levels, and flow velocity.

Feeding: Behaves as an opportunistic omnivore with carnivorous tendencies, adapting its diet dynamically according to seasonal prey availability. Its trophic spectrum is exceptionally broad, consisting of benthic invertebrates such as bivalve mollusks and gastropods—notably preying on the invasive golden mussel Limnoperna fortunei—aquatic insect larvae, decapod crustaceans like freshwater crabs and shrimps, organic detritus, and plant debris. Larger individuals frequently engage in piscivory, targeting small teleost fish and establishing themselves as prominent benthic predators within their native food webs.

Behavior: Displays primarily crepuscular and nocturnal activity patterns, during which it actively roams the river bottom in search of food. It relies heavily on its highly sensitive tactile and chemical barbels to navigate and locate prey in turbid or dark waters. During daylight hours, it remains inactive, seeking shelter in deep pools or underneath submerged structures. It is a gregarious species that forms dense schools, especially during seasonal migratory movements. The sharp dorsal and pectoral spines serve as a potent active defense mechanism against larger aquatic predators.

Reproduction: Operates as a broadcast spawner with external fertilization, offering no parental care to its progeny. This species engages in potamodromous migration, traveling upstream in large schools during the spring and summer months (typically from October to March) to locate suitable spawning grounds in open, flowing river channels. Females release high quantities of small, non-adhesive eggs into the water column, where they are fertilized by males. The pelagic eggs and developing larvae drift downstream with the currents toward shallow, nutrient-rich marginal lagoons and floodplains that serve as nursery areas.

Conservation status: Classified as a species of Least Concern (LC) on global and regional conservation lists due to its wide distribution and high relative abundance. However, local populations face persistent anthropic pressures, including intense commercial and recreational fishing, habitat fragmentation caused by hydroelectric dams that block migratory routes, and environmental degradation from agricultural and industrial runoff entering the major South American river basins.