''Corydoras pygmaeus'', or the pygmy corydoras or pygmy catfish is a

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 ...

and

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 ...

fish belonging to the subfamily Corydoradinae of 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 ...

. It originates in tropical inland waters 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 ...

, and is found in the

Madeira River The Madeira River ( pt, Rio Madeira, link=no ) is a major waterway in South America. It is estimated to be in length, while the Madeira-Mamoré is estimated near or in length depending on the measuring party and their methods. The Madeira is ...

basin in

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

Taxonomy

The first scientific description of the pygmy corydoras was published in 1966 by German biologist and physician

Joachim Knaack Joachim (; ''Yəhōyāqīm'', "he whom Yahweh has set up"; ; ) was, according to Christian tradition, the husband of Saint Anne and the father of Mary, the mother of Jesus. The story of Joachim and Anne first appears in the Biblical apocryphal ...

, in ''Aquarien und Terrarien-Zeitschrift''. One specimen was designated the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

and one additional specimen was collected as a

paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype nor a syntype). Of ...

. The scientific name uses the Latin word ''pygmaeus'', meaning dwarf or pygmy. A species of Corydoras with a similar appearance, ''

Corydoras hastatus The dwarf corydoras (''Corydoras hastatus''), dwarf catfish, tail spot pygmy catfish, or micro catfish is a tropical freshwater fish belonging to the subfamily Corydoradinae of the family Callichthyidae. It originates in inland waters in South Am ...

'' was described in the 1880s, and many specimens that were described as ''Corydoras hastatus'' between the 1920s and 1950s were subsequently found to be misidentified specimens of the pygmy corydoras. In older literature, the pygmy corydoras is frequently mislabeled due to ''Corydoras hastatus'' being the only miniature ''Corydoras'' species known at the time.

Description

The pygmy corydoras is a silver-colored fish, with an unbroken black line that runs horizontally along the center of the sides of the fish from the tip of its snout to its caudal peduncle. It has a second thin black line along the lower part of the side of the body, from behind the ventral fins and continuing into the tail. The top part of the body has a light black or dark gray shading that starts on the top of its snout and ends at the tail. Newly hatched fry have vertical stripes along the sides of their bodies that fade by the end of their first month, when the horizontal stripes of the adult fish begin to appear. The maximum length of the species is about , but typical adult sizes are for males and for females. In addition to their larger length, females are also rounder and broader than males, especially when they have eggs. Young fry grow rapidly after hatching, reaching in six to eight weeks.

Distribution and habitat

The pygmy corydoras is widely distributed in inland waters in Peru in tributaries of the

Nanay River The Nanay River is a river in northern Peru. It is a tributary of the Amazon River, merging into this river at the city of Iquitos. The lower part of the Nanay flows to the north and west of the city, while the Itaya River flows to the south and ...

, in Ecuador in tributaries of the

Aguarico River The Aguarico River ( es, Río Aguarico, meaning "rich water") is a river in northeastern Ecuador. It is the main river of the Sucumbíos province. In the last part of its course it is the Ecuadorian-Peruvian border. It empties into the Napo Riv ...

, and in western Brazil in tributaries of the

. The holotype was obtained from Calama, Brazil, along the Madeira River near the mouth of the

Ji-Paraná River The Ji-Paraná River (Machado River), sometimes spelled Jiparaná, is a river in Rondônia state in western Brazil. It is a tributary of the Madeira River in the Amazon Basin. For much of its length it runs roughly parallel with the northeastern ...

. The pygmy corydoras lives in a

climate in water with a 6.0 - 8.0 pH, a water hardness of 2 – 25 dGH, and a temperature range of . It feeds on

worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete wor ...

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

s, and

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

matter.

Breeding

The pygmy corydoras lays approximately 100 eggs at a time. The female holds 2–4 eggs at a time in a pouch formed by her pelvic fins while they are fertilized by the male, which takes about 30 seconds. The female swims to a safe location with the fertilized eggs, where she attaches the sticky eggs to a surface, where they will remain.

In captivity

It is a peaceful fish, shoaling fish and can be kept in a

community aquarium Community aquaria are tanks that are designed to contain more than one species of fish. Most commonly they include a variety of species that do not normally occur together in nature, for example angelfish from Brazil, swordtails from Mexico, and ...

of smaller fish species such as ember tetras. It can be fed most sinking foods, flakes, frozen food and sinking wafers. It can be kept with small shrimp and snails. In aquariums, they are often kept on fine grained substrate, such as sand. This enables them to dig through the substrate without injury to their

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 ...

, which can often be lost in sharp substrates. They are often kept at a pH of between 6.5 and 7.0. They are schooling fish that are usually kept in groups of at least four and will also behave much more naturally in larger groups (10 or more). Unlike the larger more common ''Corydoras'', they often swim in shoals around the mid water and lower regions of the tank. ''C. pygmaeus'' are peaceful fish which will not thrive with aggressive tankmates. They are perhaps best kept in a planted species tank, or with shrimp such as ''Neocaridina'' spp. They seem to do best when offered live foods in addition to prepared food items. Appropriate foods include

microworm The free-living nematode ''Panagrellus redivivus'' (sour paste nematode, or beer mat nematode from its occurrence in constantly moist felt beer mats), is known to many aquarium enthusiasts and fish keepers as the microworm. It is a tiny roundwor ...

s or similar

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

s, as well as ''

Artemia ''Artemia'' is a genus of aquatic crustaceans also known as brine shrimp. It is the only genus in the family Artemiidae. The first historical record of the existence of ''Artemia'' dates back to the first half of the 10th century AD from Urmia La ...

'' nauplii (newly hatched brine shrimp).

References

{{Taxonbar, from=Q244281 Corydoras Taxa named by Joachim Knaack Fish described in 1966 Fish of South America