Lithoxus
Encyclopedia
Lithoxus is a genus
of catfish
es (order
Siluriformes) of the family
Loricariidae
. It includes eight species
, L. boujardi, L. bovallii, L. jantjae, L. lithoides, L. pallidimaculatus, L. planquettei, L. stocki, and L. surinamensis.
sister to Exastilithoxus
. Together, these two genera form a well-supported clade
.
drainage along the border between Brazil
and French Guiana
, through Suriname
west to the Tacutu River along the border between Guyana
and Brazil and south to the Uatama
and Trombetas
rivers of Brazil. L. boujardi originates from the Approuague
and Oyapock River basins in French Guiana. L. bovallii inhabits the Ireng River
basin in the upper Negro River drainage in Guyana
. L. lithoides is distributed in the Essequibo in Guyana and the upper Corantijn River basin in Suriname. L. pallidimaculatus is from the Suriname River
basin in Suriname. L. planquettei is known from Atlantic coastal drainages from the Maroni
to the Kaw River basins in French Guiana. L. stocki originates from the Maroni and Mana River
basins in French Guiana. L. surinamensis inhabits the Gran Rio River basin in the upper Suriname River drainage in Suriname.
In 2008, the discovery of L. jantjae spread the known distribution of the genus to include the Orinoco River; this species is restricted to the Ventuari River
above Tencua Falls.
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
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 gonad
s.
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
s on the leading edge of the pectoral fin spine.
Lithoxus species grow to about 4.1–8.6 centimetres (1.6–3.4 in
) SL
.
, 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. L. boujardi frequently occurs in fast flowing waters of principal rivers or creeks where the substrate is rock or sand. L. bovallii, L. lithoides, and L. surinamensis live in stony rivulets. L. lithoides clings to rocks in the rapids. L. planquettei has been found in little forest tributaries (3–4 metres or 9–13 ft wide) with shallow depth, a rocky bottom, and a strong current, often with cascades. In the dry season, L. planquettei has been found in a split brook with very little water input, suggesting that it is a pioneer species
which is capable of colonizing difficult environments which are nutritionally poor.
Lithoxus have a unique air-holding stomach. Lithoxus (along with its sister, Exastilithoxus) are fairly unique 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.
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 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...
es (order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Siluriformes) of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Loricariidae
Loricariidae
Loricariidae is the largest family of catfish , with almost 700 species and new species being described each year. Loricariids originate from fresh water habitats of Costa Rica, Panama, and tropical and subtropical South America. These fish are noted for the bony plates covering their bodies and...
. It includes eight species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, L. boujardi, L. bovallii, L. jantjae, L. lithoides, L. pallidimaculatus, L. planquettei, L. stocki, and L. surinamensis.
Taxonomy
Lithoxus is supported as a monophyleticMonophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
sister to Exastilithoxus
Exastilithoxus
Exastilithoxus is a small genus of catfish of the family Loricariidae. It includes two species, E. fimbriatus and E. hoedemani.-Distribution and habitat:...
. Together, these two genera form a well-supported clade
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
.
Distribution
Lithoxus range from the OyapockOyapock River
The Oyapock or Oiapoque River is a 370-km long river in South America that forms most of the border between French Guiana and the Brazilian state of Amapá...
drainage along the border between 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...
and French Guiana
French Guiana
French Guiana is an overseas region of France, consisting of a single overseas department located on the northern Atlantic coast of South America. It has borders with two nations, Brazil to the east and south, and Suriname to the west...
, through Suriname
Suriname
Suriname , officially the Republic of Suriname , is a country in northern South America. It borders French Guiana to the east, Guyana to the west, Brazil to the south, and on the north by the Atlantic Ocean. Suriname was a former colony of the British and of the Dutch, and was previously known as...
west to the Tacutu River along the border between Guyana
Guyana
Guyana , officially the Co-operative Republic of Guyana, previously the colony of British Guiana, is a sovereign state on the northern coast of South America that is culturally part of the Anglophone Caribbean. Guyana was a former colony of the Dutch and of the British...
and Brazil and south to the Uatama
Uatumã River
The Uatumã River is a river flowing through the state of Amazonas in the Manaus area of Brazil.A tributary of the Amazon River, it is known for its extensive peacock population. ....
and Trombetas
Trombetas
The Trombetas is a river on the northern side of the Amazon River. Its confluence with the Amazon is just north of the town of Óbidos, Pará in Brazil. It has its sources in the Guyana highlands, but its long course is frequently interrupted by violent currents, rocky barriers, and rapids...
rivers of Brazil. L. boujardi originates from the Approuague
Approuague River
The Approuague river is a major river in French Guiana. Itruns north from the Tumuk Humak Mountains to the Atlantic Ocean, almost parallel with the Oiapoque, with its mouth in Pointe Béhague or Cumarumã....
and Oyapock River basins in French Guiana. L. bovallii inhabits the Ireng River
Ireng River
The Ireng River forms part of Guyana's western border with Brazil. It flows through the valleys of the Pakaraima Mountains for most of its length. It is the only major river in Guyana which flows from North to South. It is one of the northernmost tributaries of the Amazon river system.It is...
basin in the upper Negro River drainage in Guyana
Guyana
Guyana , officially the Co-operative Republic of Guyana, previously the colony of British Guiana, is a sovereign state on the northern coast of South America that is culturally part of the Anglophone Caribbean. Guyana was a former colony of the Dutch and of the British...
. L. lithoides is distributed in the Essequibo in Guyana and the upper Corantijn River basin in Suriname. L. pallidimaculatus is from the Suriname River
Suriname River
The Suriname River is 480 km long and flows through the country Suriname. Its sources are located in the Guiana Highlands on the border between the Wilhelmina Mountains and the Eilerts de Haan Mountains...
basin in Suriname. L. planquettei is known from Atlantic coastal drainages from the Maroni
Maroni River
The Maroni or Marowijne is a river in South America. It originates in the Tumuk Humak Mountains and forms the border between French Guiana and Suriname...
to the Kaw River basins in French Guiana. L. stocki originates from the Maroni and Mana River
Mana River
Mana is a river in the Krasnoyarsk Krai making a confluence with the Yenisey River in 16 km from the Krasnoyarsk city. It is the second largest river in the Krasnoyarsk neighborhood after Yenisey....
basins in French Guiana. L. surinamensis inhabits the Gran Rio River basin in the upper Suriname River drainage in Suriname.
In 2008, the discovery of L. jantjae spread the known distribution of the genus to include the Orinoco River; this species is restricted to the Ventuari River
Ventuari River
The Ventuari River is a river in the Orinoco basin in Venezuela. The Ventuari flows from eastern Venezuela in the Guiana Highlands southwest into the Orinoco River. It is 520 km long and its major tributary is the Manapiare River.-References:...
above Tencua Falls.
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
Pylorus
The pylorus is the region of the stomach that connects to the duodenum . It is divided into two parts:* the pyloric antrum, which connects to the body of the stomach.* the pyloric canal, which connects to the duodenum....
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 gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
s.
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
Odontode
Odontodes, or dermal teeth, are hard structures found on the external surfaces of animals or near internal openings. They comprise a soft pulp surrounded by dentine and covered by a mineralized substance such as enamel, a structure similar to that of teeth. They generally do not have the same...
s on the leading edge of the pectoral fin spine.
Lithoxus species grow to about 4.1–8.6 centimetres (1.6–3.4 in
Inch
An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...
) 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:...
.
Ecology
Lithoxus species are rheophilicRheophile
A rheophile is an organism that prefers to live in fast moving water.-Insects:*Many aquatic insects living in riffles require current to survive.*Epeorus sylvicola, a rheophilic mayfly species .-Fish:...
, 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. L. boujardi frequently occurs in fast flowing waters of principal rivers or creeks where the substrate is rock or sand. L. bovallii, L. lithoides, and L. surinamensis live in stony rivulets. L. lithoides clings to rocks in the rapids. L. planquettei has been found in little forest tributaries (3–4 metres or 9–13 ft wide) with shallow depth, a rocky bottom, and a strong current, often with cascades. In the dry season, L. planquettei has been found in a split brook with very little water input, suggesting that it is a pioneer species
Pioneer species
Pioneer species are species which colonize previously uncolonized land, usually leading to ecological succession. They are the first organisms to start the chain of events leading to a livable biosphere or ecosystem...
which is capable of colonizing difficult environments which are nutritionally poor.
Lithoxus have a unique air-holding stomach. Lithoxus (along with its sister, Exastilithoxus) are fairly unique 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.