''Homodiaetus'' 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 pencil catfishes native to

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 ...

Species

There are currently four recognized species in this genus: * '' Homodiaetus anisitsi''

Eigenmann Eigenmann is a surname. Notable persons with that surname include: * Andi Eigenmann (born 1990), Filipino actress * Carl H. Eigenmann (1863–1927), German–American ichthyologist, husband of Rosa Eigenmann * Eduardo de Mesa Eigenmann, birth name ...

& Ward, 1907 * '' Homodiaetus banguela'' Koch, 2002 * '' Homodiaetus graciosa'' Koch, 2002 * '' Homodiaetus passarellii'' ( Miranda-Ribeiro, 1944)

Distribution

The distribution of ''Homodiaetus'' is restricted you southeastern

, from

Uruguay Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...

Paraguay River The Paraguay River (Río Paraguay in Spanish, Rio Paraguai in Portuguese, Ysyry Paraguái in Guarani) is a major river in south-central South America, running through Brazil, Bolivia, Paraguay and Argentina. It flows about from its headwaters in ...

s in the west to the coastal drainages of the

Rio de Janeiro State Rio de Janeiro () is one of the 27 federative units of Brazil. It has the second largest economy of Brazil, with the largest being that of the state of São Paulo. The state, which has 8.2% of the Brazilian population, is responsible for 9.2% of ...

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 ...

. ''H. anisitsi'' originates from the Paraná-Paraguay River basin. ''H. banguela'' inhabits the São João River and ''H. passarellii'' is known from coastal basins in the State of Rio de Janeiro. ''H. graciosa'' is distributed in coastal basins of southeastern Brazil in states of Paraná and

São Paulo São Paulo (, ; Portuguese for 'Saint Paul') is the most populous city in Brazil, and is the capital of the state of São Paulo, the most populous and wealthiest Brazilian state, located in the country's Southeast Region. Listed by the GaWC a ...

Description

''Homodiaetus'' is currently distinguished from other genera of

Stegophilinae The Stegophilinae are a subfamily of catfishes (order Siluriformes) of the family Trichomycteridae. It includes 12 genera: '' Acanthopoma'', '' Apomatoceros'', '' Haemomaster'', '' Henonemus'', '' Homodiaetus'', '' Megalocentor'', ''Ochmacanthus ...

by the combination of the origin of the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

midlength between the tip of the snout and the caudal-fin origin, the

opercle The operculum is a series of bones found in bony fish and chimaeras that serves as a facial support structure and a protective covering for the gills; it is also used for respiration and feeding. Anatomy The opercular series contains four bon ...

with three or more odontodes, and the

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

membranes confluent with the isthmus. ''Homodiaetus'' species are small and grow up to 42 millimetres (1.7 in) SL. They are transparent with the except of the head and abdomen. ''Homodiaetus'' species have a thin body and depressed head that is almost as wide as the head is long. The dorsal and ventral profiles are straight except for a convex head. The mouth is inferior. ''H. anisitsi'' has three dark bands on its caudal fin, while dark lines are irregular or absent in the other three species. Among the other three species, ''H. graciosa'' has 5–6 rows of teeth in the dentary (vs. 6–7 in the other two species). ''H. graciosa'' has 7–9 (usually 8) opercular odontodes, ''H. passarellii'' has 6–7, and ''H. banguella'' has 9.

Ecology

''Homodiaetus'' species are found in

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') a ...

s and arenaceous rivers of little depth. These fish are known to be

lepidophagous Lepidophagy is a specialised feeding behaviour in fish that involves eating the scales of other fish. Lepidophagy is widespread, having evolved independently in at least five freshwater families and seven marine families. A related feeding behavi ...

, meaning they feed upon scales.

References

{{Taxonbar, from=Q5891083 Trichomycteridae Fish of South America Fauna of Brazil Freshwater fish genera Catfish genera Taxa named by Carl H. Eigenmann