''Lithoxus'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of
suckermouth armored catfishes native 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 ...
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 sout ...
.
Taxonomy
''Lithoxus'' is supported as a
monophyletic sister
A sister is a woman or a girl who shares one or more parents with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a family, familial relationship, it is sometimes used endearingly to r ...
to ''
Exastilithoxus''. Together, these two genera form a well-supported
clade.
Species
There are currently eight recognized species in this genus:
* ''
Lithoxus boujardi''
So. Muller & Isbrücker, 1993
* ''
Lithoxus bovallii''
(Regan
The family name Regan, along with its cognates O'Regan, O Regan, Reagan, and O'Reagan, is an Anglicized form of the Irish surname Ó Riagáin or Ó Ríogáin, from Ua Riagáin. The meaning is likely to have originated in ancient Gaelic ''ri'' ...
, 1906)
* ''
Lithoxus jantjae''
Lujan, 2008
* ''
Lithoxus lithoides''
C. H. Eigenmann, 1912
* ''
Lithoxus pallidimaculatus''
Boeseman, 1982
* ''
Lithoxus planquettei''
Boeseman, 1982
* ''
Lithoxus stocki''
Nijssen & Isbrücker, 1990
* ''
Lithoxus surinamensis''
Boeseman, 1982
Distribution
''Lithoxus'' range from the
Oyapock
The Oyapock or Oiapoque (; ; ) is a long river in South America that forms most of the border between the French overseas department of French Guiana and the Brazilian state of Amapá.
Course
The Oyapock runs through the Guianan moist fores ...
drainage along the border between
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 ...
and
French Guiana
French Guiana ( or ; french: link=no, Guyane ; gcr, label=French Guianese Creole, Lagwiyann ) is an overseas department/region and single territorial collectivity of France on the northern Atlantic coast of South America in the Guianas. ...
, through
Suriname west to the
Tacutu River along the border between
Guyana and Brazil and south to the
Uatama and
Trombetas
The Trombetas is a large river on the northern side of the Amazon River.
Course
The Trombetas is long, and is navigable by 500 ton vessels for a stretch of . The Trombetas river gives birth to very many rivers, including the Anamu river.
It is ...
rivers of Brazil.
Description
''Lithoxus'' contains some of the most dorsoventrally flattened fishes in the world.
They can be distinguished from most loricariids by having a round instead of oval lower lip. The lower lip is large and round as in ''Exastilithoxus'' with the edge sometimes frilled, but not with the barbels seen in ''Exastilithoxus''.
''Lithoxus'' species have a unique, enlarged, thin-walled stomach from which the intestine exits dorsally.
The stomach is expanded, thin-walled, and clear and is used in breathing air. A thin, clear tube exits the main body of the stomach anterodorsally, terminating at the
pylorus
The pylorus ( or ), or pyloric part, connects the stomach to the duodenum. The pylorus is considered as having two parts, the ''pyloric antrum'' (opening to the body of the stomach) and the ''pyloric canal'' (opening to the duodenum). The ''pylori ...
just anterior to the posterior extent of the stomach. The intestine tends to have less coils than other members of Ancistrini. The expanded stomach is slightly larger in males; this is due to the males having more space due to a difference in the relative size of the
gonads.
Colouration in ''Lithoxus'' species is typically slate gray to tan with a few lighter markings on the body; there are occasionally bands in the pectoral and caudal fins. The ventral surface ranges from white to slightly lighter than the sides. The abdomen is naked (scaleless and unplated). The caudal fin is slightly forked.
Breeding males develop extremely long
odontode
Odontodes, or dermal teeth, are hard structures found on the external surfaces of animals or near internal openings. They consist of a soft pulp surrounded by dentine and covered by a mineralized substance such as enamel, a structure similar to th ...
s on the leading edge of the pectoral fin spine.
Ecology
''Lithoxus'' species are
rheophilic
A rheophile is an animal that prefers to live in fast-moving water.
Examples of rheophilic animals
Insects
*Many aquatic insects living in riffles require current to survive.
*'' Epeorus sylvicola'', a rheophilic mayfly species ( Ephemeropter ...
, meaning they prefer to inhabit fast-moving water.
''Lithoxus'' is said to inhabit both rivulets and medium-sized creeks. ''Lithoxus'' have been collected from riffles on the main-stem Essequibo River in Guyana. These peripheral habitats are among the first parts of the river to dry and the respiratory stomach may have evolved to handle this periodic drying.
The flattened morphology suggests that ''Lithoxus'' species live under rocks.
''Lithoxus'' have a unique air-holding stomach.
''Lithoxus'' (along with its sister, ''Exastilithoxus'') are fairly unusual among loricariids in that they subsist entirely on a diet of insect larvae.
The large size and small number of eggs suggest that parental care is well developed, but nothing is known of the breeding habits of ''Lithoxus''.
References
{{Taxonbar, from=Q5021407
Ancistrini
Fish of South America
Fish of Brazil
Fauna of the Guianas
Fish of French Guiana
Fish of Suriname
Catfish genera
Taxa named by Carl H. Eigenmann
Freshwater fish genera