''Corydoras'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
freshwater
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
catfish
Catfish (or catfishes; order Siluriformes or Nematognathi) 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 three largest species alive, ...
in the family
Callichthyidae
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 ...
and subfamily
Corydoradinae
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 s ...
. The species usually have more restricted areas of
endemism
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
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 ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Cos ...
where ''Corydoras'' is not present.
''Corydoras'' species are distributed in
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
where they can be found from the east of the
Andes
The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
to the
Atlantic
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...
coast, from
Trinidad
Trinidad is the larger and more populous of the two major islands of Trinidad and Tobago. The island lies off the northeastern coast of Venezuela and sits on the continental shelf of South America. It is often referred to as the southernmos ...
to the
Río de la Plata drainage in northern
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
.
[ Species assigned to ''Corydoras'' display a broad diversity of body shapes and coloration.][ ''Corydoras'' are small fish, ranging from in SL.,][ and are protected from predators by their body armor and by their sharp, typically venomous spines.
]
Taxonomy
The name ''Corydoras'' is derived from the Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
''kory'' (helmet) and ''doras'' (skin). ''Corydoras'' is by far the largest genus of Neotropical
The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone.
Definition
In bioge ...
fishes with more than 160 species.[ It is the sole genus in the tribe Corydoradini.][ ''C. difluviatilis'' is recognized as the ]basalmost
In phylogenetics, basal is the direction of the ''base'' (or root) of a rooted phylogenetic tree or cladogram. The term may be more strictly applied only to nodes adjacent to the root, or more loosely applied to nodes regarded as being close to th ...
species of Corydoradini, exhibiting several plesiomorphic features compared to the other species of ''Corydoras''. The type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
for this genus is ''Corydoras geoffroy''.[ Several hundred species are not yet classified, but kept by ]aquarists
Fishkeeping is a popular hobby, practiced by aquarists, concerned with keeping fish in a home aquarium or garden pond. There is also a piscicultural fishkeeping industry, serving as a branch of agriculture.
Origins of fishkeeping
Fish have ...
. These species are given 'C-numbers', originally devised by Hans-Georg Evers for the German fishkeeping magazine '' DATZ'' in 1993. In 2006, 153 C-numbers had been assigned, of which 32 had been assigned appropriate scientific names.
The species ''C. barbatus'', ''C. macropterus'' and ''C. prionotos'' have been reclassified into the genus ''Scleromystax
''Scleromystax'' is a genus of fish in the family Callichthyidae endemic to small tributaries from several coastal river basins draining the southern and southeastern regions in Brazil. Most of the species of ''Scleromystax'' are highly sexually ...
''.[Britto, M.R. (2003)]
Phylogeny of the subfamily Corydoradinae Hoedeman, 1952 (Siluriformes: Callichthyidae), with a definition of its genera.
''Proceedings of the Academy of Natural Sciences of Philadelphia, 153 (1): 119-154.'' ''Brochis
''Corydoras'' is a genus of freshwater catfish in the family Callichthyidae and subfamily Corydoradinae. The species usually have more restricted areas of endemism than other callichthyids, but the area of distribution of the entire genus almo ...
'' had been differentiated from ''Corydoras'' due to the higher number of dorsal fin
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...
rays; however, ''Brochis'' has recently been suggested to be a synonym
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
of ''Corydoras''.[ This is contested and has not been universally accepted. The ]sixray corydoras
The sixray corydoras (''Aspidoras pauciradiatus'') or false corydoras is a tropical freshwater fish belonging to the Corydoradinae sub-family of the family Callichthyidae. It originates in inland waters in South America, and is found in the upper ...
belongs in ''Aspidoras
''Aspidoras'' is a genus of catfishes of the family Callichthyidae from Brazil.
Taxonomy
The type species for this genus is '' Aspidoras rochai''. The name ''Aspidoras'' is derived from the Greek ''aspis'' (shield) and ''dora'' (skin).
''Aspido ...
''.
''Brochis''
''Brochis'' is a formerly recognized genus of catfish. Between one and three fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
of the Callichthyidae
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 ...
in the Siluriformes
Catfish (or catfishes; order Siluriformes or Nematognathi) 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 three largest species alive, ...
order are referred to as ''Brochis'', however following recent classification these three species have been grouped in the genus ''Corydoras''. The genus is considered defunct by most scientific authorities, or as a junior synonym or subgenus of ''Corydoras''. Consequently, it is an example of Obsolete taxa
Despite being considered defunct, there are several morphological differences that fish formerly classified in the genus ''Brochis'' have. These include a noticeably larger body, a more lyre-like tail and most decisively, the extended dorsal fins that have more rays than those of ''Corydoras'' ''Corydoras'' have 7-10 rays on their dorsal fins, while Brochis have 10–18. ''Brochis'' are very large for their family, as all three species can exceed 8 centimetres in length.
In the ''Brochis'' stable, ''Corydras splendens'' is the largest. It is also the largest ''Corydoras'' attaining a maximum size of 9.9 centimetres and 40 grams
Ecology
''Corydoras'' are generally found in smaller-sized streams
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...
, along the margins of larger river
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...
s, in marsh
A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found at ...
es, and in pond
A pond is an area filled with water, either natural or artificial, that is smaller than a lake. Defining them to be less than in area, less than deep, and with less than 30% emergent vegetation helps in distinguishing their ecology from th ...
s.[ They are native to slow-moving and almost still (but seldom stagnant) streams and small rivers of ]South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
, where the water is shallow and very murky. 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 Corydoras are found. They inhabit a wide variety of water types but tend toward soft, neutral to slightly acidic or slightly alkaline pH and 5-10 degrees of ]hardness
In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...
. 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, these species are active during the daytime.][ ''Corydoras'' are capable of breathing both water and air, often swimming to the surface to quickly ingest air before re-submerging. The frequency of this air breathing behavior increases when Corydoras are exposed to water with low oxygen availability, allowing them to tolerate periods of aquatic hypoxia.
Their main food is bottom-dwelling insects and insect larvae and various worms, as well as some vegetable matter. Although no Corydoras are ]piscivorous
A piscivore () is a carnivorous animal that eats primarily fish. The name ''piscivore'' is derived . Piscivore is equivalent to the Greek-derived word ichthyophage, both of which mean "fish eater". Fish were the diet of early tetrapod evoluti ...
, they will eat flesh from dead fishes. Their feeding method is to search the bottom with their sensory barbels
In fish anatomy and turtle anatomy, a barbel is a slender, whiskerlike sensory organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the zebrafish, the black dragonfish and some s ...
and suck up food items with their mouth, often burying their snout up to their eyes.
In several species of ''Corydoras'', it has been observed that the fishes, after initial evasive reaction to threat, lie still; this is suggested to be a form of cryptic behavior. However, it is also argued that most species do not have cryptic coloration nor freezing behavior and continue to exist,[ likely due to their armor and venom. A few species of '']Otocinclus
''Otocinclus'' is a genus of catfish in the family Loricariidae native to South America, commonly known as "dwarf suckers" or "otos". This genus, like other loricariids, is characterized by rows of armour plating covering the body, as well as the ...
'': ('' O. affinis'', '' O. flexilis'', '' O. mimulus'' and '' O. xakriaba'') are considered to be Batesian mimic
Batesian mimicry is a form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species directed at a predator of them both. It is named after the English naturalist Henry Walter Bates, after his work on bu ...
s of certain ''Corydoras'' species (''C. diphyes'', ''C. garbei'', ''C. nattereri'' and ''C. paleatus'', respectively). These species have bony plates of armor and strong, frequently venomous spines as defenses, making them less palatable; by mimicking these species in size and coloration, ''Otocinclus'' avoid predation.[Axenrot, T.E. & Kullander, S.O. (2003)]
''Corydoras diphyes'' (Siluriformes: Callichthyidae) and ''Otocinclus mimulus'' (Siluriformes: Loricariidae), two new species of catfishes from Paraguay, a case of mimetic association.
''Ichthyological Exploration of Freshwaters, 14 (3): 249–272.''
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
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...
. 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 genus is well known among aquarists for its many ornamental species. They are well suited to tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
freshwater community aquariums, as they get along well with other species and are not aggressive. ''Corydoras'' are quite timid and are recommended to be kept in shoals of six or more. Corydoras 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 Corydoras 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
Nitrate is a polyatomic ion
A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
levels. This ion leads to the infection of the barbels
In fish anatomy and turtle anatomy, a barbel is a slender, whiskerlike sensory organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the zebrafish, the black dragonfish and some s ...
, which will shorten and become useless. The barbels may also be affected by constant contact with a sharp substrate. Contrary to popular belief, these fish can be kept in a tank with gravel, as long as there are no sharp edges on the gravel without affecting their barbels, although they do prefer sand substrate. 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. It is a myth that salt cannot be used on this species of fish as a means of parasite medication. Salt can be added to the water of the Corydoras catfish in order to rid the fish of ich. These fish are fairly easy to keep, being peaceful, 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
In zoology, a crepuscular animal is one that is active primarily during the twilight period, being matutinal, vespertine, or both. This is distinguished from diurnal and nocturnal behavior, where an animal is active during the hours of daylig ...
rather than nocturnal and activity can even peak at twilight. ''Corydoras'' are a very popular choice 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.
Species
There are currently 161 recognized extant
Extant is the opposite of the word extinct. It may refer to:
* Extant hereditary titles
* Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English
* Extant taxon, a taxon which is not extinct, ...
species in this genus, as well as one known extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
species:
See also
* List of ''Corydoras'' species
* List of freshwater aquarium fish species
References
{{Taxonbar, from=Q147894
Catfish genera
Freshwater fish genera
Fishkeeping
Callichthyidae
Paleocene fish
Taxa named by Bernard Germain de Lacépède
Extant Thanetian first appearances