Callichthyidae
Encyclopedia
Callichthyidae is a family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of 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...

es (order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Siluriformes), called armored catfishes due to the two rows of bony plates (or scutes) running down the length of the body. This family contains some of the most popular freshwater aquarium fish, such as the Corydoras
Corydoras
Members of the South American Corydoras genus are freshwater temperate and tropical catfish in the armored catfish family , and are commonly referred to as corydorases, cories, or cory catfish.-Taxonomy:...

.

Taxonomy

The family derives its name from the Greek words kallis (beautiful) and ichthys (fish). Callichthyidae is one of six families in the superfamily Loricarioidea
Loricarioidea
Loricarioidea is a superfamily of catfishes . It contains the six families Trichomycteridae, Nematogenyiidae, Callichthyidae, Scoloplacidae, Astroblepidae, and Loricariidae. Some schemes also include Amphiliidae...

. It is sister to a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 formed by Scoloplacidae, Astroblepidae, and Loricariidae
Loricariidae
Loricariidae is the largest family of catfish , with almost 700 species and new species being described each year. Loricariids originate from fresh water habitats of Costa Rica, Panama, and tropical and subtropical South America. These fish are noted for the bony plates covering their bodies and...

. Within the family Callichthyidae, there are two subfamilies with eight genera and about 177 species. They account for about 7% of all catfish. Most of these species are in the genus Corydoras, the largest catfish genus.

The subfamily Corydoradinae includes about 90% of the species in the family Callichthyidae and is one of the most diverse siluriform assemblages in the Neotropics, with approximately 170 valid species. It includes two tribes, Aspidoradini and Corydoradini. Aspidoradini contains Aspidoras
Aspidoras
Aspidoras is a genus of catfishes of the family Callichthyidae.-Taxonomy:The type species for this genus is Aspidoras rochai...

and Scleromystax
Scleromystax
Scleromystax is a genus of catfishes of the family Callichthyidae. It includes several species including, S. barbatus, S. macropterus, S. prionotos, and S. salmacis.-Taxonomy:...

, while Corydoradini contains Corydoras
Corydoras
Members of the South American Corydoras genus are freshwater temperate and tropical catfish in the armored catfish family , and are commonly referred to as corydorases, cories, or cory catfish.-Taxonomy:...

and Brochis
Brochis
Brochis is a genus of freshwater catfish in the Corydoradinae sub-family of the Callichthyidae family in order Siluriformes. The type species is the emerald catfish, Brochis splendens. The name Brochis is derived from the Greek word "brogchia", meaning "throat" or "trachea".These fish are often...

. Some believe that the genus Brochis should be synonymized
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...

 with Corydoras.

The subfamily Callichthyinae contains Callichthys
Callichthys
Callichthys is a small genus of freshwater catfish in the Callichthyinae subfamily of the armored catfish family, and consists of 4 species from South America. The genus Callichthys is distributed in most freshwater drainages of South America....

, Dianema
Dianema
Dianema is a small genus of freshwater catfish in the Callichthyinae subfamily of the armored catfish family, and consists of two species, D. longibarbis and D. urostriatum. The type species for this genus is Dianema longibarbis. The name is derived from the Greek di, meaning "two", and nema,...

, Hoplosternum
Hoplosternum
Hoplosternum is a small genus of freshwater catfish in the Callichthyinae subfamily of the armored catfish family, and consists of 3 species from South America, H. littorale, H. magdalenae, and H...

, Lepthoplosternum
Lepthoplosternum
Lepthoplosternum is a small genus of freshwater catfish in the Callichthyinae subfamily of the armored catfish family, and consists of six species.-Taxonomy:...

, and Megalechis
Megalechis
Megalechis is a small genus of freshwater catfish in the Callichthyinae subfamily of the armored catfish family, and consists of 2 species.-Taxonomy:The type species for this genus is Callichthys thoracatus...

. According to a 1997 paper, 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. In a 2004 study, different relationships among the callichthyines were found: Dianema + Hoplosternum form the most basal clade, and Callichthys is sister
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

 to Lepthoplosternum + Megalechis.

Fossil record

The first known fossil species of callichthyid is Corydoras revelatus
Corydoras revelatus
Corydoras revelatus is an extinct species of callichthyid known from a single specimen found in Late Paleocene strata of the Mais Gordo Formation in Salta, Argentina. According to chronological dating of the strata, the fossil specimen is about 58.2–58.5 million years old.Compared to modern...

from Salta
Salta
Salta is a city in northwestern Argentina and the capital city of the Salta Province. Along with its metropolitan area, it has a population of 464,678 inhabitants as of the , making it Argentina's eighth largest city.-Overview:...

, Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 of the late Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...

. This species is tentatively placed in Corydoras, but is unambiguously a member of the subfamily Corydoradinae. It indicates that the lineages leading to the two callichthyid subfamilies occurred at least by the late Paleocene. It also suggests an earlier differentiation of loricarioids
Loricarioidea
Loricarioidea is a superfamily of catfishes . It contains the six families Trichomycteridae, Nematogenyiidae, Callichthyidae, Scoloplacidae, Astroblepidae, and Loricariidae. Some schemes also include Amphiliidae...

 in comparison to other catfishes, or a lack of older fossils of other Neotropical groups.

A fossil identified as a Hoplosternum sp. has also been identified from the middle Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 in the La Venta
La Venta
La Venta is a pre-Columbian archaeological site of the Olmec civilization located in the present-day Mexican state of Tabasco. Some of the artifacts have been moved to the museum "Parque - Museo de La Venta", which is in Villahermosa, the capital of Tabasco....

 formation, Magdalena River
Magdalena River
The Magdalena River is the principal river of Colombia, flowing northward about through the western half of the country. It takes its name from the biblical figure Mary Magdalene. It is navigable through much of its lower reaches, in spite of the shifting sand bars at the mouth of its delta, as...

 basin, Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

.

Distribution

The Neotropical family Callichthyidae is found in most 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...

n river drainages (Paraná
Paraná River
The Paraná River is a river in south Central South America, running through Brazil, Paraguay and Argentina for some . It is second in length only to the Amazon River among South American rivers. The name Paraná is an abbreviation of the phrase "para rehe onáva", which comes from the Tupi language...

-Paraguay
Paraguay River
The Paraguay River is a major river in south central South America, running through Brazil, Bolivia, Paraguay, and Argentina...

, São Francisco
São Francisco River
The São Francisco is a river in Brazil. With a length of , it is the longest river that runs entirely in Brazilian territory, and the fourth longest in South America and overall in Brazil...

, Atlantic Coastal basins in Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

, Amazon
Amazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...

, Orinoco
Orinoco
The Orinoco is one of the longest rivers in South America at . Its drainage basin, sometimes called the Orinoquia, covers , with 76.3% of it in Venezuela and the remainder in Colombia...

, Maracaibo
Lake Maracaibo
Lake Maracaibo is a large brackish bay in Venezuela at . It is connected to the Gulf of Venezuela by Tablazo Strait at the northern end, and fed by numerous rivers, the largest being the Catatumbo. It is commonly considered a lake rather than a bay or lagoon, and at 13,210 km² it would be the...

, Magdalena
Magdalena River
The Magdalena River is the principal river of Colombia, flowing northward about through the western half of the country. It takes its name from the biblical figure Mary Magdalene. It is navigable through much of its lower reaches, in spite of the shifting sand bars at the mouth of its delta, as...

), as well as in a few rivers in Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...

. They present highest diversity in the headwaters of the Amazonas drainage and those rivers draining the Guiana Shield.

The subfamily Corydoradinae has a predominantly cis
Cis
Cis may have the following meanings:* "Cis-" as a prefix of Latin origin, meaning "on the same side [as]" or "on this side [of]", with several derived usages:** In chemistry, cis- refers to cis-trans isomerism...

-Andean
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

 distribution north of the Rio de La Plata
Río de la Plata
The Río de la Plata —sometimes rendered River Plate in British English and the Commonwealth, and occasionally rendered [La] Plata River in other English-speaking countries—is the river and estuary formed by the confluence of the Uruguay River and the Paraná River on the border between Argentina and...

 system, in Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

. Representatives of the Corydoradinae are found in several freshwater environments, ranging from fast-flowing piedmont streams with sandy or rocky bottom to lowland pools with muddy bottom.

Description

Callichthyids are fairly small catfish, and range in size from some tiny Corydoras species that do not exceed 2 centimetre (0.78740157480315 in) to Hoplosternum littorale
Hoplosternum littorale
Hoplosternum littorale a species of catfish belonging to the Callichthyinae subfamily of the family Callichthyidae. It is known as tamuatá in Brazil, atipa in French Guiana, hassar in Guyana, kwi kwi in Suriname, cascadu in Trinidad, and busco or currito in Venezuela.-Description:H...

, which some sources list as growing to a length of up to 24 centimetres (9.4 in) TL
Fish measurement
Fish measurement refers to the measuring of the length of individual fish and of various parts of their anatomy. These data are used in many areas of ichthyology, including taxonomy and fisheries biology.-Overall length:...

. The mouth is small and ventral with one or two pairs of well-developed barbels. The dorsal
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

 and pectoral fins have strong spines, and there is a spine at the anterior border of the adipose fin.

The scutes that give these fish their namesake are one of the most obvious characteristics of these fish. The body has two rows of overlapping bony plates on each side. These plates are arranged so they overlap along the rows, as well as between the rows, giving full protection, but at the same time allowing some freedom of movement. These scutes connect with the solid bones of the head, and the head itself may be covered with bony plates. The upper row of lateral scutes may either meet on the back or there may be a narrow bare area that may be filled in with small oval or roundish bony platelets.

Species of the Corydoradinae are of small size (maximum about 9 centimetres (3.5 in) in standard length
Fish measurement
Fish measurement refers to the measuring of the length of individual fish and of various parts of their anatomy. These data are used in many areas of ichthyology, including taxonomy and fisheries biology.-Overall length:...

) and are easily distinguished from other callichthyids by their deep bodies and short maxillary barbels
Barbel (anatomy)
A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...

.

Ecology

Living habits are varied; the family includes both bottom-foraging and mid-water species. Callichthyids inhabit a wide range of habitats, from small, swift, oxygen-rich creeks to big rivers and flooded areas. Their habitats may even include swampy and muddy habitats where oxygen may be virtually absent. Callichthyids survive in these conditions by breathing air; air is collected at the water surface and swallowed. The intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...

s are used to absorb oxygen, and the air is expelled from the anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...

. The anterior digestive intestine packages digesta into a string of slightly compressed bolus
Bolus (digestion)
In digestion, a bolus is a mass of food that has been chewed at the point of swallowing. Once a bolus reaches the stomach, digestion begins....

es, creating an air channel in the digestive intestine, thus allowing air to pass unimpeded. The posterior intestine is modified for respiration into a thin-walled and highly vascularized structure by reduction of the thickness of the epithelium, submucosa and muscle layers; though highly modified to absorb air, it is inefficient for digestive purposes. Air moving through the digestive tract facilitates the movement of digesta to the rectum
Rectum
The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...

. Unlike other catfish such as loricariids
Loricariidae
Loricariidae is the largest family of catfish , with almost 700 species and new species being described each year. Loricariids originate from fresh water habitats of Costa Rica, Panama, and tropical and subtropical South America. These fish are noted for the bony plates covering their bodies and...

 or trichomycterids
Trichomycteridae
Trichomycteridae is a family of catfishes commonly known as the pencil or parasitic catfishes. This family includes the infamous candiru fish, feared by some people for its alleged habit of entering into the urethra of humans....

 that may breathe air only under hypoxic
Hypoxia (environmental)
Hypoxia, or oxygen depletion, is a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system...

 conditions, callichthyids breathe air under all water conditions. Some callichthyids are able to absorb air through their hindgut to move short distances on land. Air stored in their digestive tracts also accounts for 75% of the necessary air for neutral buoyancy
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...

.

Breeding habits are also variable. Corydoradines breed over the substrate (such as rocks, logs, or leaves) as most catfish. However, the members of the subfamily Callichthyinae are known for building and guarding floating foam bubble nest
Bubble nest
Bubblenests, also spelled bubble nests or bubble-nests, created by some fish species, are floating masses of bubbles blown with an oral secretion, saliva bubbles, and occasionally aquatic plants, or an area for egg deposit attached at the bottom. Fish that build and guard bubble nests are known as...

s; Hoplosternum littorale
Hoplosternum littorale
Hoplosternum littorale a species of catfish belonging to the Callichthyinae subfamily of the family Callichthyidae. It is known as tamuatá in Brazil, atipa in French Guiana, hassar in Guyana, kwi kwi in Suriname, cascadu in Trinidad, and busco or currito in Venezuela.-Description:H...

is reported to have the most complex nest structure. These floating nests are made of foam and vegetal 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 sperms, 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. Some callichthyids, especially species of Corydoras, are popular as ornamental fish in the fishkeeping
Fishkeeping
Fishkeeping is a popular hobby concerned with keeping fish in a home aquarium or garden pond. There is also a fishkeeping industry, as a branch of agriculture.-Types of fishkeeping systems:...

 hobby
Hobby
A hobby is a regular activity or interest that is undertaken for pleasure, typically done during one's leisure time.- Etymology :A hobby horse is a wooden or wickerwork toy made to be ridden just like a real horse...

.
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