The Corydoras genus includes more than 142 species, all of which live in South America. Together with a number of other genera, they form the family Callachtidae or Armored Catfish.
The genus name Corydoras consists of two parts: ‘Cory’ means ‘helmet’ and ‘doras’ means ‘skin’. The name is a reference to the double row of bony plates under the skin on the flank of this genus. These bony plates act as a kind of armour, hence the common collective name for this group of fish: Armored Catfish. By possessing the bony plates, they do not need any further protection, so they do not have scales.
Together with the spiky anterior dorsal ray and pectoral fin rays, they make a tricky bite for predators.
All Corydoras species can also survive in deoxygenated water. They then shoot to the surface and take a gulp of air that is forced through the intestines. The intestines then absorb oxygen from the water.
Sexing Corydoras is sometimes a bit difficult. Usually, the female is a bit bigger and plumper than the male. Also, the dorsal fin is often slightly different in shape. The dorsal fin is somewhat pointed in the male and somewhat rounded in the female.