Lithoxus

Taxobox
name = "Lithoxus"
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Siluriformes
familia = Loricariidae
subfamilia = Hypostominae
tribus = Ancistrini
genus = "Lithoxus"
genus_authority = Eigenmann, 1910
type_species = "Lithoxus lithoides"
type_species_authority = Eigenmann, 1910
subdivision_ranks = Binomial name
subdivision =
"Lithoxus boujardi"
Muller & Isbrücker, 1993
"Lithoxus bovallii"
(Regan, 1906)
"Lithoxus jantjae"
Lujan, 2008
"Lithoxus lithoides"
Eigenmann, 1910
"Lithoxus pallidimaculatus"
Boeseman, 1982
"Lithoxus planquettei"
Boeseman, 1982
"Lithoxus stocki"
Nijssen & Isbrücker, 1990
"Lithoxus surinamensis"
Boeseman, 1982


synonyms = "Paralithoxus" Boeseman, 1982

"Lithoxus" is a genus of catfishes (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".cite journal|journal=Neotropical Ichthyology|volume=6|issue=3|pages=413-418|year=2008|title=Description of a new "Lithoxus" (Siluriformes: Loricariidae) from the Guayana Highlands with a discussion of Guiana Shield biogeography|first=Nathan K.|last=Lujan] cite journal|url=http://silurus.acnatsci.org/ACSI/library/biblios/2007_Ferraris_Catfish_Checklist.pdf|title=Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types|first=Carl J., Jr.|last=Ferraris|journal=Zootaxa|volume=1418|pages=1–628|year=2007|format=PDF]

Taxonomy

"Lithoxus" is supported as a monophyletic sister to "Exastilithoxus". Together, these two genera form a well-supported clade.

Distribution

"Lithoxus" range from the Oyapock 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.

Description

"Lithoxus" contains some of the most dorsoventrally flattened fishes in the world.cite web|url=http://www.auburn.edu/academic/science_math/res_area/loricariid/fish_key/Lithoxus/lithoxus.html|title="Lithoxus" Eigenmann, 1910|first=Jonathan W.|last=Armbruster|accessdate=2007-07-24] 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 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.cite journal|url=http://www.auburn.edu/academic/science_math/res_area/loricariid/fish_key/Air.pdf|title=Modifications of the Digestive Tract for Holding Air in Loricariid and Scoloplacid Catfishes|journal=Copeia|year=1998|issue=3|pages=663–675|format=PDF]

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 odontodes 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.FishBase species|genus=Lithoxus|species=boujardi|year=2007|month=July] FishBase species|genus=Lithoxus|species=bovallii|year=2007|month=July] FishBase species|genus=Lithoxus|species=lithoides|year=2007|month=July] FishBase species|genus=Lithoxus|species=pallidimaculatus|year=2007|month=July] FishBase species|genus=Lithoxus|species=planquettei|year=2007|month=July] FishBase species|genus=Lithoxus|species=stocki|year=2007|month=July] FishBase species|genus=Lithoxus|species=surinamensis|year=2007|month=July]

Ecology

"Lithoxus" species are rheophilic, 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".

References