Megalechis
Encyclopedia
Megalechis is a small genus
of freshwater
catfish
in the Callichthyinae subfamily of the armored catfish
family, and consists of 2 species.
for this genus is Callichthys thoracatus. The name is derived from the Greek
megas, meaning "great", and the Greek echis, meaning "viper".
No uniquely derived features are known for Megalechis.
A change in the synonymy
of the species of Megalechis occurred in 2005. It is especially confusing because the name M. thoracata remains valid, but applies to the species formerly known as M. personata, which becomes a new junior synonym of M. thoracata. On the other hand, the species formerly known as M. thoracata is now named M. picta.
in the northern portion of South America
, including the Amazonas
and Orinoco
rivers, as well as the coastal drainages of the Guyanas
. M. picta occurs east of the Andes in the Amazon, Orinoco, and upper Essequibo River
basins, and coastal rivers of northern Brazil
. M. thoracata is found east of the Andes in the Amazon, Orinoco, and upper Paraguay River
basins, as well as in the coastal rivers of the Guianas and northern Brazil. Recent introductions were recorded in the upper Paraná River
drainage.
spine, the anal fin with six (rarely five) branched rays instead of an anal fin with five, rarely four, branched rays, and the caudal fin dotted or dusky often with a clearer band at the base of rays versus a caudal fin with a conspicuous transverse dark band and
dark distal border. Megalechis species grow to about 12–15 centimetre
s SL
.
Reproductive males have an extremely developed pectoral fin spine, like that of Hoplosternum littorale
. In M. thoracata, males are also larger than females.
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 2 species.
Taxonomy
The type speciesBiological 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 Callichthys thoracatus. The name 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;...
megas, meaning "great", and the Greek echis, meaning "viper".
No uniquely derived features are known for Megalechis.
A change in the synonymy
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 the species of Megalechis occurred in 2005. It is especially confusing because the name M. thoracata remains valid, but applies to the species formerly known as M. personata, which becomes a new junior synonym of M. thoracata. On the other hand, the species formerly known as M. thoracata is now named M. picta.
Distribution
Both species of Megalechis are distributed east of the AndesAndes
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...
in the northern portion 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...
, including the Amazonas
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...
and 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...
rivers, as well as the coastal drainages of the Guyanas
Guyanas
Guyana is a country in South America.Guyana, Guayana, or Guiana may also refer to:*Guayana Esequiba, the territory of Guyana claimed by Venezuela*Guayana Region, an administrative region of Venezuela...
. M. picta occurs east of the Andes in the Amazon, Orinoco, and upper Essequibo River
Essequibo River
The Esequibo River is the largest river in Guyana, and the largest river between the Orinoco and Amazon. Rising in the Acarai Mountains near the Brazil-Guyana border, the Essequibo flows to the north for 1,010 km through forest and savanna into the Atlantic Ocean.-Geography:There are countless...
basins, and coastal rivers of northern 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...
. M. thoracata is found east of the Andes in the Amazon, Orinoco, and upper Paraguay River
Paraguay River
The Paraguay River is a major river in south central South America, running through Brazil, Bolivia, Paraguay, and Argentina...
basins, as well as in the coastal rivers of the Guianas and northern Brazil. Recent introductions were recorded in the upper Paraná River
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...
drainage.
Description
M. thoracata is distinguished from M. picta by a comparatively shorter dorsal finDorsal 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...
spine, the anal fin with six (rarely five) branched rays instead of an anal fin with five, rarely four, branched rays, and the caudal fin dotted or dusky often with a clearer band at the base of rays versus a caudal fin with a conspicuous transverse dark band and
dark distal border. Megalechis species grow to about 12–15 centimetre
Centimetre
A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...
s 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:...
.
Reproductive males have an extremely developed pectoral fin spine, like that of 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...
. In M. thoracata, males are also larger than females.