Pilcomayo

This species is normally referred to as A. paraguayensis, but that name has been considered a synonym of A. nattereri since 2003. Confusion remains however, as the type locality for the latter is 'Villa Bella', now known as Parintins, a settlement on the main Amazon river channel between Manaus and Santarém and many kilometres away from the majority of confirmed localities.

It exhibits slightly different behaviour to the majority of congeners in that it tends to swim in midwater and spends a large proportion of its time away from the substrate. Its morphology exhibits corresponding adaptations towards a pelagic existence with a relatively large eye, a more terminal mouth position, more strongly-forked caudal-fin, and more symmetrical body shape than most other Corydoras species.

Widely-distributed throughout much of the Paraná and Uruguay river systems in Brazil, Paraguay, Argentina and Uruguay. Some records from Buenos Aires province, Argentina are now considered to refer to the congener H. togoi (Miquelarena and López, 2006) so the common vernacular name 'Buenos Aires tetra' may not...

Famed as a rapacious predator capable of rapidly stripping flesh from bone and a danger to any animal entering its native waters, P. nattereri is among the most notorious freshwater fishes in the world. As a result, displays featuring this “bloodthirsty” creature are found in most public aquaria, grisly Hollywood movies have been released, and the species has become popular in the aquarium trade. Little of this infamy is based on factual evidence, however.