Phreatobius

Taxobox
name = "Phreatobius"
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Siluriformes
familia = "incertae sedis"
genus = "Phreatobius"
genus_authority = Goeldi, 1905
type_species = "Phreatobius cisternarum"
type_species_authority = Goeldi, 1905
subdivision_ranks = Species
subdivision = "P. cisternarum"
"P. dracunculus"
"P. sanguijuela"

"Phreatobius" is a genus of catfishes (order Siluriformes).

Taxonomy

For quite some time "Phreatobius cisternarum" was the only species in the genus. However, two new species were described relatively recently in 2007, "Phreatobius dracunculus" and "Phreatobius sanguijuela".cite journal|title=A new subterranean species of "Phreatobius" Goeldi, 1905 (Siluriformes, Incertae sedis) from the Southwestern Amazon basin|first=Oscar Akio|last=Shibatta|coauthors=Muriel-Cunha, Janice; de Pinna, Mário C.C.|journal=Papéis Avulsos de Zoologia|Volume=47|issue=17|pages=191-201|year=2007] cite journal|title=A new phreatic catfish of the genus "Phreatobius" Goeldi 1905 from groundwaters of the Iténez River, Bolivia (Siluriformes: Heptapteridae)|first=Luis|last=Fernandez|coauthors=Saucedo, Lisandro J.; Carvajal-Vallejos, Fernando M.; Schaefer, Scott A.|journal=Zootaxa|volume=1626|pages=51–58|year=2007]

"Phreatobius" has been classified with a number of different families: Clariidae, Plotosidae, Trichomycteridae, Cetopsidae, and Pimelodidae. Most recently, it has been classified in Heptapteridae. Its phylogenetic position remains uncertain.cite journal|url=http://www.scielo.br/pdf/paz/v45n26/a01v4526.pdf|title=New data on Cistern Catfish, "Phreatobius cisternarum", from subterranean waters at the mouth of the Amazon River (Siluriformes, Incertae Sedis)|last=Muriel-Cunha|first=Janice|coauthors=de Pinna, Mário|journal=Papéis Avulsos de Zoologia|format=PDF|publisher=Museu de Zoologia da Universidade de São Paulo|pages=327-339|volume=35|year=2005|id=ISSN: 1807-0205] The family placement of the genus has remained problematic and thus it is not classified in any of the existing families.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]

An undescribed species of "Phreatobius" lives in leaf litter. "Phreatobius walkeri", a "nomen nudum", is provided by the Guinness Book of World Records, to describe this fish that stays on land for extended periods of time. [cite web|url=http://www.planetcatfish.com/catelog/species.php?species_id=646|title=Cat-eLog: "Phreatobius sp."|publisher=PlanetCatfish.com|date=2004-12-20|accessdate=2007-04-09] Two additional quite distinctive species of "Phreatobius", as yet undescribed, are known from the Río Negro of Brazil.

Distribution and habitat

"Phreatobius" species all live underground and are known only from artificial wells penetrating near-surface aquifers of the Amazon River basin. The genus has one of the widest distribution of any hypogean fish genus, with "P. sanguijuela" from the upper Amazon, some 2000 km from reported locations of "P. cisternarum" near the Amazon River mouth, and "P. dracunculus" also approximately 1900 km from the Rio Branco drainage area.

Description

This genus can be recognized by the combination of characteristics, such as their dorsal and anal fins being continuous with a rounded caudal fin, unbranched anal fin rays, a projecting lower jaw, bright red coloration, a lack of the dorsal fin spine locking mechanism, the first pectoral fin ray being soft instead of spinous. Most of these traits are rare or unusual among vast groups of catfish.

All three species look extremely similar. However, in "P. cisternarum" the eyes are tiny, while "P. dracunculus" and "P. sanguijuela" lack eyes altogether. The two eyeless species can be differentiated by fin-ray and vertebrae counts. It is also described that "P. dracunculus" is lighter in color, while "P. cisternarum" and "P. sanguijuela" are described as bright red.

References