Callichthys is a small genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of freshwater

Freshwater

Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 catfish

Catfish

Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...

 in the Callichthyinae subfamily of the armored catfish

Callichthyidae

Callichthyidae is a family of catfishes , called armored catfishes due to the two rows of bony plates running down the length of the body. This family contains some of the most popular freshwater aquarium fish, such as the Corydoras.-Taxonomy:The family derives its name from the Greek words kallis...

 family, and consists of 4 species from South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

. The genus Callichthys is distributed in most freshwater drainages of South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

.

Taxonomy

The type species

Biological type

In biology, a type is one particular specimen of an organism to which the scientific name of that organism is formally attached...

 for this genus is Silurus callichthys

Callichthys callichthys

The cascarudo , armored catfish, bubblenest catfish, hassar, or mailed catfish is a subtropical freshwater fish belonging to the Callichthyinae sub-family of the Callichthyidae family.-Taxonomy:...

. The name Callichthys is derived from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 kallos (beautiful) and ichthys (fish). 3 of the 4 species were described only relatively recently.

The genus Callichthys is in need of taxonomic work, as it includes 13 nominal species but specimens of this genus are usually referred to as C. callichthys regardless of collecting locality.

Callichthys is the most basal

Basal (phylogenetics)

In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

 member of the subfamily Callichthyinae.

Description

The genus Callichthys can be readily distinguished from other callichthyids by having the coracoids covered by skin and not exposed ventrally, the infraorbital

Infraorbital

Infraorbital is an anatomical term which means, literally, inferior to the eye socket . Some examples of uses of the term are:* Infraorbital artery* Infraorbital foramen* Infraorbital canal* Infraorbital groove...

 bones also covered by skin, and the head highly depressed with less than 75% of the cleithral

Cleithrum

The cleithrum is a membrane bone which first appears as part of the skeleton in primitive bony fish, where it runs vertically along the scapula. Its name is derived from Greek κλειθρον = "key ", by analogy with "clavicle" from Latin clavicula = "little key".In modern fishes, the cleithrum is a...

 width (except sometimes in mature males).

Ecology

Callichthys is normally found in large schools on the muddy bottoms of slow-moving rivers, pools, drainage ditches, and swampy areas. In water with low oxygen content, the fish are capable of utilizing atmospheric air by taking in a gulp of air at the surface of the water and passing it back to the hind gut. The walls of the gut are lined with tiny blood vessels into which the oxygen from the air can pass, similar to the function of true lungs. The remaining gasses pass out through the anus. When there is a severe drought, these air breathers are able to traverse short stretches of land seeking better conditions. The fish is also capable of making sounds; both grunts and squeaks.

In the aquarium

Spawning has been accomplished in the aquarium. Callichthys is a builder of bubblenests from plant parts, some bottom materials, and bubbles formed by a mouth secretion and air. The male forms a mass of bubbles about 20 cm (8 in) in diameter and 10 cm (4 in) high. During the time of construction, the female is actively chased away or ignored. When the nest construction is complete, the male will accept the female. The eggs (up to several hundred) are deposited into the nest and the male or the pair will actively protect the nest for about four weeks until the fry come out of the nest at the size of 2.5 cm (1 in).