Members of the South American Corydoras 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...

 are 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...

In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...

 and tropical 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 armored catfish
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 (Corydoradinae subfamily), and are commonly referred to as corydorases, cories, or cory catfish.


The name Corydoras 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;...

 kory (helmet) and doras (skin). Corydoras is by far the largest genus of Neotropical fishes with more than 142 species. In addition, many variants exist. It is the sole genus in the tribe Corydoradini. C. difluviatilis is recognized as the basalmost
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:...

 species of Corydoradini, exhibiting several plesiomorphic features compared to the other species of Corydoras. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 for this genus is Corydoras geoffroy
Corydoras geoffroy
Corydoras geoffroy is a tropical freshwater fish belonging to the Corydoradinae sub-family of the Callichthyidae family. It originates in coastal rivers in South America, and is found in Suriname and French Guiana...

. Several hundred Corydoras species are not yet classified, but kept by aquarists
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...

. These species are given C-Numbers, originally devised by Hans-Georg Evers for the German fishkeeping magazine DATZ in 1993. In 2006, there were 153 C-numbers assigned, of which 32 had been assigned appropriate scientific names.

The C. barbatus, C. macropterus, and C. prionotos have been reclassified into the genus 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:...

. Brochis had been differentiated from Corydoras due to the higher number of dorsal fin
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...

 rays; however, 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...

has recently been suggested to be a synonym
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...

 of Corydoras. This is contested and has not been universally accepted. The sixray corydoras
Sixray corydoras
The sixray corydoras or false corydoras is a tropical freshwater fish belonging to the Corydoradinae sub-family of the Callichthyidae family. It originates in inland waters in South America, and is found in the upper Araguaia River basin in Brazil...

 belongs in Aspidoras
Aspidoras is a genus of catfishes of the family Callichthyidae.-Taxonomy:The type species for this genus is Aspidoras rochai...



The species of Corydoras usually have more restricted areas of endemism than other callichthyids, but the area of distribution of the entire genus almost equals the area of distribution of the family, except for 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...

 where Corydoras is not present. Corydoras species are distributed east of the 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...

 to the Atlantic coast, from Trinidad
Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...

 to the Río 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...

 drainage in northern 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...

. The genus is also widely distributed in South America from the 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, in 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...

, and occurs in a variety of environments.


Species assigned to Corydoras display a broad diversity of body shapes and coloration. Corydoras are small fish, ranging from 25 to 120 millimetres (1.0–4.7 in) SL
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:...



Corydoras are generally found in smaller-sized streams, along the margins of larger rivers, in marshes and ponds. They are native to slow-moving and almost still (but seldom stagnant) streams and small rivers 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...

 where the water is shallow and very clear. Most species are bottom-dwellers, foraging in sand, gravel, or detritus. The banks and sides of the streams are covered with a dense growth of plants, and this is where the corys are found. They inhabit a wide variety of water types but tend toward soft, neutral to slightly acidic or slightly alkaline pH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 and 5-10 degrees of hardness
Hard water
Hard water is water that has high mineral content . Hard water has high concentrations of Ca2+ and Mg2+ ions. Hard water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling...

. They can tolerate only a small amount of salt (some species tolerate none at all) and do not inhabit environments with tidal influences. They are often seen in shoals. Most species prefer being in groups and many species are found in schools or aggregations of hundreds or even thousands of individuals, usually of a single species, but occasionally with other species mixed in. Unlike most catfishes which are nocturnal, Corydoras species are active during the daytime.

Their main food is bottom-dwelling insects and insect larvae and various worms, as well as some vegetable matter. Although no corys are piscivorous, they will eat flesh from dead fishes. Their feeding method is to search the bottom with their sensory barbels and suck up food items with their mouth, often burying their snout up to their eyes, one of the reasons a soft sand substrate is preferable.

In several species of Corydoras, it has been observed that the fishes, after initial evasive reaction to threat, lay still; this is suggested to be a form of cryptic behavior
In ecology, crypsis is the ability of an organism to avoid observation or detection by other organisms. It may be either a predation strategy or an antipredator adaptation, and methods include camouflage, nocturnality, subterranean lifestyle, transparency, and mimicry...

. However, it is also argued that most species do not have cryptic coloration nor freezing behavior and continue to exist.

A few Otocinclus
Otocinclus is a genus of catfish of the family Loricariidae commonly called "dwarf suckers" or "otos". Otocinclus originate from tropical, freshwater rivers in South America.-Taxonomy:...

species (O. mimulus, O. flexilis, O. affinis, and O. xakriaba) are considered to be Batesian mimic
In evolutionary biology, mimicry is the similarity of one species to another which protects one or both. This similarity can be in appearance, behaviour, sound, scent and even location, with the mimics found in similar places to their models....

s of certain Corydoras species (C. diphyes, C. paleatus
Corydoras paleatus
Corydoras paleatus is a species of catfish of the family Callichthyidae. Its common names include peppered cat, pepper cory or salt & pepper cory. It originates from the lower Paraná River basin and coastal rivers in Uruguay and Brazil.-Description:This fish species reaches about...

, C. nattereri, and C. garbei, respectively). These Corydoras species have bony plates of armor and strong spines as defenses, making them less palatable; by mimicking these species in size and coloration, Otocinclus avoid predation.

A unique form of insemination has been described in Corydoras aeneus. When these fish reproduce, the male will present his abdomen to the female. The female will attach her mouth to the male's genital opening, creating the well-known "T-position" many Corydoras exhibit during courtship. The female will then drink the sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...

. The sperm rapidly moves through her intestines and is discharged together with her eggs into a pouch formed by her pelvic fins. The female can then swim away and deposit the pouch somewhere else alone. Because the T-position is exhibited in other species than just C. aeneus, it is likely that this behavior is common in the genus.

In the aquarium

The Corydoras genus is well known among aquarists for its many ornamental species. They are well suited to tropical freshwater community aquariums, as they get along well with other species and are not at all aggressive. Some types of Corydoras are quite timid and are recommended to be kept in shoals of three upwards. Corys are mostly bottom feeders, so they should be offered sinking pellets as well as supplements of live and frozen foods. If flake foods are used, care should be taken to prevent all food from being eaten by faster moving fish at the higher levels of the tank.

Most corys prefer soft, acidic water. They can, however, tolerate a wide range of water conditions, including temperatures that are cooler than tropical. They do not do well in fish tanks with high nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

 levels. This ion leads to the infection of the barbels, which will shorten and become useless. The barbels may also be affected by constant contact with a sharp substrate
Substrate (aquarium)
The substrate of an aquarium refers to the material used on the tank bottom. It can affect water chemistry, filtration, and the well-being of the aquarium's inhabitants, and is also an important part of the aquarium's aesthetic appeal...

. They are more likely to thrive if there is an open area of substrate on the bottom of the tank where they can obtain submerged food.

These fish are easy to keep, being peaceful, small, hardy, active, and entertaining. Occasionally they will dart to the surface, sticking their snout above the water for an instant to take a "breath" of air. This behavior is perfectly normal and is not an indication that anything is wrong with the fish. However, If this is done in excess, it can indicate poor water conditions.

Where investigated Corydoras sp. have been shown to be diurnal and crepuscular
Crepuscular animals are those that are active primarily during twilight, that is during dawn and dusk. The word is derived from the Latin word crepusculum, meaning "twilight." Crepuscular is, thus, in contrast with diurnal and nocturnal behavior. Crepuscular animals may also be active on a bright...

rather than nocturnal and activity can even peak at twilight. Corydoras are very good choices for a community aquarium, and are widely kept throughout the world. Their longevity in the aquarium is noteworthy; C. aeneus is said to have lived 27 years in captivity and 20 years is not too uncommon.
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