''Pygidianops'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

pencil catfish Trichomycteridae is a family of catfishes commonly known as pencil catfishes or parasitic catfishes. This family includes the candiru fish (''Vandellia cirrhosa''), feared by some people for its alleged habit of entering into the urethra of hum ...

native to

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

Species

There are four recognized species in this genus: * '' Pygidianops amphioxus''

de Pinna De Pinna was a high-end clothier for men and women founded in New York City in 1885, by Alfred De Pinna (1831–1915), a Sephardic Jew born in England. They also sold menswear-inspired clothing for women that was finely tailored. The flagship sto ...

& Kirovsky, 2011 * '' Pygidianops cuao''

Schaefer Schaefer is an alternative spelling and cognate for the German word ''schäfer'', meaning 'shepherd', which itself descends from the Old High German '' scāphare''. Variants "Shaefer", "Schäfer" (a standardized spelling in many German-speaking ...

, Provenzano,

& Baskin, 2005 * '' Pygidianops eigenmanni''

Myers Myers as a surname has several possible origins, e.g. Old French ("physician"), Old English ("mayor"), and Old Norse ("marsh"). People * Abram F. Myers (1889–after 1960), chair of the Federal Trade Commission and later general counsel and b ...

, 1944 * '' Pygidianops magoi''

, Provenzano,

& Baskin, 2005

Distribution

''P. eigenmanni'' is from the Rio Negro basin in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. ''P. cuao'' is known only from

Cuao River Cuao River is a river of Venezuela. It is part of the Orinoco River basin. See also *List of rivers of Venezuela This is a list of rivers in Venezuela. By drainage basin This list is arranged by drainage basin, with respective tributaries inden ...

drainage basin. ''P. magoi'' is known only from lower

Orinoco The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers approximately 1 million km2, with 65% of it in Venezuela and 35% in Colombia. It is the List of rivers by discharge, f ...

mainstem between

Ciudad Bolívar Ciudad Bolívar (; Spanish for "Bolivar City"), formerly known as Angostura and St. Thomas de Guyana, is the capital of Venezuela's southeastern Bolívar, Venezuela, Bolívar State. It lies at the spot where the Orinoco River narrows to about ...

and Barrancas in

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

Description

Species of ''Pygidianops'' share the extreme reduction of pigmentation, loss of the

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

, the loss or extreme reduction of

pectoral fins Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only b ...

, a reduced

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelia ...

, and the reduction or complete loss of eyes in some species. These fish are markedly miniaturized, yet retain a relatively well-ossified skeleton comparable in both bone differentiation and degree of calcification to that observed in larger trichomycterids. ''P. cuao'' is distinguished from congeners by the presence of diminutive eyes (vs. eyes absent in both other species), posterior naris absent (vs. nares bilaterally paired), and the presence of a triangular skin flap at mouth corner (vs. skin flap absent). ''P. magoi'' is distinguished from all congeners by the absence of pectoral and anal fins (vs. fins present), posterior naris absent (vs. present, nares bilaterally paired), four laterosensory pores on the head (vs. six), and by the presence of 9–10 caudal fin rays (vs. 12–13). With all of its fins lost except the caudal fin, ''P. magoi'' represents the most extreme fin loss among ostariophysans. ''P. eigenmanni'' lacks eyes but has its anal and pectoral fins.

References

{{Taxonbar, from=Q7262999 Trichomycteridae Catfish of South America Freshwater fish genera Catfish genera Taxa named by George S. Myers