Phreatobius
Encyclopedia
Phreatobius is a genus
of catfish
es (order
Siluriformes).
was the only species
in the genus. However, two new species were described relatively recently in 2007, Phreatobius dracunculus
and Phreatobius sanguijuela
.
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. The family
placement of the genus has remained problematic and thus it is not classified in any of the existing families.
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. Two additional quite distinctive species of Phreatobius, as yet undescribed, are known from the Río Negro of Brazil.
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.
, 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.
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).
Taxonomy
For quite some time Phreatobius cisternarumPhreatobius cisternarum
Phreatobius cisternarum is a species of catfish in the genus Phreatobius. This Brazilian fish is one of the few fish species that live underground in phreatic habitats. It has proved problematic in its classification, which remains uncertain....
was the only 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...
in the genus. However, two new species were described relatively recently in 2007, Phreatobius dracunculus
Phreatobius dracunculus
Phreatobius dracunculus is a species of catfish in the genus Phreatobius.P. dracunculus was discovered from an artificial well in the village of Rio Pardo, located in the drainage area of the Rio Branco ....
and Phreatobius sanguijuela
Phreatobius sanguijuela
Phreatobius sanguijuela is a species of catfish in the genus Phreatobius.This species was discovered in a hand-dug well in located within the Río Paraguá drainage, a tributary of the Río Iténez in Bolivia. This species is endangered by environmental degradation due to pollution, water extraction...
.
Phreatobius has been classified with a number of different families: Clariidae, Plotosidae, Trichomycteridae
Trichomycteridae
Trichomycteridae is a family of catfishes commonly known as the pencil or parasitic catfishes. This family includes the infamous candiru fish, feared by some people for its alleged habit of entering into the urethra of humans....
, Cetopsidae
Cetopsidae
Cetopsidae is a small family of catfishes , commonly called the whale catfishes.-Taxonomy:This family contains five genera. It is divided into two subfamilies, Cetopsinae and Helogeneinae. Helogeneinae was previously a family-level group, but now it has been reclassified as a subfamily of Cetopsidae...
, and Pimelodidae
Pimelodidae
Pimelodidae, commonly known as the long-whiskered catfishes, is a family of catfishes .-Taxonomy:Pimelodidae has undergone much revision. Currently, the family contains about 30 genera and about 90 recognized and known but unnamed species...
. Most recently, it has been classified in Heptapteridae
Heptapteridae
Heptapteridae is a family of catfish that originate from Mexico to South America. Heptapteridae is derived from Greek, hepta meaning seven and pteron meaning fin....
. Its phylogenetic
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
position remains uncertain. 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...
placement of the genus has remained problematic and thus it is not classified in any of the existing families.
An undescribed species of Phreatobius lives in leaf litter. Phreatobius walkeri, a nomen nudum
Nomen nudum
The phrase nomen nudum is a Latin term, meaning "naked name", used in taxonomy...
, is provided by the Guinness Book of World Records
Guinness World Records
Guinness World Records, known until 2000 as The Guinness Book of Records , is a reference book published annually, containing a collection of world records, both human achievements and the extremes of the natural world...
, to describe this fish that stays on land for extended periods of time. 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 RiverAmazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...
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
Branco River
The Rio Branco is the principal affluent of the Rio Negro from the north; it is enriched by many streams from the sierras which separate Venezuela and Guyana from Brazil. Its two upper main tributaries are the Urariquira and the Takutu...
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 finFish anatomy
Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does.- Body :...
, unbranched anal fin
Fish anatomy
Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does.- Body :...
rays, a projecting lower jaw, bright red coloration, a lack of the dorsal fin
Fish anatomy
Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does.- Body :...
spine locking mechanism, the first pectoral fin
Fish anatomy
Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does.- Body :...
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.