Callichthyidae is a family of catfishes (order Siluriformes), called armored catfishes due to the two rows of bony plates (or scutes) along the lengths of their bodies. It contains some of the most popular freshwater aquarium fish, such as many species in the genus Corydoras.
Taxonomy
The family derives its name from the Greek words (, 'beautiful') and (, 'fish'). Callichthyidae is one of six families in the superfamily Loricarioidea, and is sister to a clade formed by Scoloplacidae, Astroblepidae, and Loricariidae.
Subdivisions
Callichthyidae is divided into two subfamilues and the following genera:
The following cladogram shows the position of the genera within the subfamily Corydoradinae.
The subfamily Callichthyinae contains Callichthys, Dianema, Hoplosternum, Lepthoplosternum, and Megalechis. According to a 1997 paper, Callichthys is the most basal member of the subfamily. In a 2004 study, different relationships among the callichthyines were found: Dianema and Hoplosternum form the most basal clade, and Callichthys is sister to Lepthoplosternum and Megalechis. In a 2013 study, Dianema is the sister group of all the remaining genera.
Fossil record
The first known fossil species of callichthyid is Corydoras revelatus from Salta, Argentina, of the late Paleocene. This species is tentatively placed in Corydoras, but is unambiguously a member of the subfamily Corydoradinae.
Description
thumb|right|Closeup photograph of Hoplosternum littorale showing overlapping bony plates
Callichthyids are fairly small catfish, and range in size from some tiny Corydoras species that do not exceed to Hoplosternum littorale, which some sources list as growing to a length of up to TL. The mouth is small and ventral with one or two pairs of well-developed barbels. The dorsal and pectoral fins have strong spines, and a spine is found at the anterior border of the adipose fin.
The scutes that give these fish their name are one of their most prominent characteristics. The body has two rows of overlapping bony plates on each side. Unlike other catfish such as loricariids or trichomycterids that may breathe air only under hypoxic conditions, callichthyids breathe air under all water conditions. These floating nests are made of foam and plant debris. Spawning and caring for the eggs and larvae takes place in these nests. Parental care in callichthyines is by the male. In Corydoras and Hoplosternum, fertilization of eggs involves 'sperm drinking'; the female and male form the "T-position" with the female's mouth over the male's genital opening, and then the female drinks the sperm, releasing the sperm and eggs simultaneously.
Relationship to humans
Some species are quite common in South America and are fished commercially. They are usually cooked in their bony armor.