Aspredinidae

The Aspredinidae are a small South American family of catfishes (order Siluriformes) also known as the banjo catfishes, with about 42 species. Aspredinids are found throughout the major tropical rivers of South America (e.g., Magdalena, Orinoco, Amazon, São Francisco, Paraguay-Paraná, and Uruguay). Bunocephalus is the only genus found in rivers west of the Andes including the Atrato, San Juan, and Patía Rivers. Of the 13 genera in the family Aspredinidae, a few genera have been described relatively recently, including Acanthobunocephalus in 1995, Micromyzon in 1996, and Pseudobunocephalus in 2008. These genera are categorized into three subfamilies. The Aspredinidae are often recognized as a part of the primarily Asian superfamily Sisoroidea as the sister group to the family Erethistidae. However, other authors find that they are sister to the superfamily Doradoidea, which includes Doradidae, Auchenipteridae, and perhaps Mochokidae. The common name of the family 'banjo catfishes' refers to their overall body shape, with a depressed head and slender caudal peduncle, that in some species gives the appearance of a banjo. Banjo catfishes lack an adipose fin. Most species lack the dorsal spine-locking mechanism. Though their bodies are scaleless, their skin is completely keratinized and is covered by large, unculiferous tubercles arranged in longitudinal rows; the entire outer layer of skin may be shed. Size ranges from less than 2.0 centimetres (.79 in) SL in Hoplomyzon papillatus to Aspredo aspredo at about 38 centimetres (15 in) SL, though most are less than 15 cm. Most species exhibit cryptic coloration. Aspredinids have a loss of alarm cells and the fright reaction that is present in other ostariophysans. Sexual dimorphism is exhibited in most species in that mature females are typically larger than males; this is, however, reversed in Hoplomyzon sexpapilostoma. Also, in Aspredo and Platystacus the dorsal fin spine is much longer in males than in females. Aspredinids live in a variety of habitats ranging from shallow backwaters to deep river channels to tidal estuaries. Some aspredinids appear to be semifossorial, during the day often resting slightly buried in leaf litter or other soft substrates. Members of the subfamily Aspredininae inhabit coastal rivers and brackish water habitats such as mangrove swamps. In general, most species are cryptically pigmented, benthic, and rather sluggish unless disturbed. Like most fish, they are able to swim by undulating their bodies; however, they also propel themselves by pumping water through their gill openings to skip along the substrate. Some species are able to produce sounds by moving their pectoral fin spines back and forth when they are agitated. Most aspredinids are generalized omnivores that feed on aquatic and terrestrial invertebrates and organic debris; however, members of Amaralia appear to specialize in feeding on the eggs of other catfishes.