Tembeassu marauna
Encyclopedia
Tembeassu marauna is a species
of weakly electric
knifefish
in the family
Apteronotidae and the only member of its genus
, known only from three specimens collected from the upper Paraná River
, Brazil
, in 1965. This fish can be identified by fleshy extensions at the tips of its upper and lower jaws, with the upper extension bearing a patch of extra teeth. The function of these unique structures is unknown, but may relate to feeding. Apparently a specialized inhabitant of deep riverine environments, T. marauna may be endangered by extensive dam
construction in the upper Paraná region.
Revue française d'Aquariologie. In 2001, James S. Albert referred this species to a monophyletic group he termed "Apteronotus
sensu stricto", which placed Tembeassu in synonymy
with Apteronotus. However, a subsequent re-examination of the original specimens by Ricardo Campos-da-Paz in 2005 found that this species does not share the derived
characters of Apteronotus; Campos-da-Paz thus returned T. marauna to its own genus
until its phylogenetic relationships can be better investigated.
and São Paulo
in 1965, during the construction of the coffer dam for the Ilha Solteira
reservoir
. These records suggest that this species inhabits deep waters in large rivers.
appendage on its back, and no dorsal
or pelvic fins. The head is long and low, with a rounded snout and a straight dorsal profile. The teeth are elongated and conical, numbering around 15 on the premaxillary bone (at the front of the upper jaw) and around 30 on the dentary bone (the lower jaw). The most distinctive feature of T. marauna is a prominent fleshy (possibly cartilaginous) extension at the tip of the upper jaw, in which approximately 15 slender teeth are loosely embedded. Another, toothless, extension is present at the tip of the lower jaw. T. marauna is mostly light brown to gray-brown.
). An alternate possibility is that they are used in feeding; similar structures in the stegophiline
catfish
es are used to gather mucus
and scales
. In common with other South America
n knifefishes, T. marauna is likely capable of generating a weak electric field
for navigation and communication.
has been extensively altered by dam construction. Thus, this species may be endangered.
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...
of weakly electric
Electric fish
An electric fish is a fish that can generate electric fields. It is said to be electrogenic; a fish that has the ability to detect electric fields is said to be electroreceptive. Most electrogenic fish are also electroreceptive. Electric fish species can be found both in the sea and in freshwater...
knifefish
Gymnotiformes
The Gymnotiformes are a group of teleost bony fishes commonly known as the Neotropical or South American knifefishes. They have long bodies and swim using undulations of their elongated anal fin...
in 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...
Apteronotidae and the only member of its genus
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...
, known only from three specimens collected from the upper Paraná River
Paraná River
The Paraná River is a river in south Central South America, running through Brazil, Paraguay and Argentina for some . It is second in length only to the Amazon River among South American rivers. The name Paraná is an abbreviation of the phrase "para rehe onáva", which comes from the Tupi language...
, 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...
, in 1965. This fish can be identified by fleshy extensions at the tips of its upper and lower jaws, with the upper extension bearing a patch of extra teeth. The function of these unique structures is unknown, but may relate to feeding. Apparently a specialized inhabitant of deep riverine environments, T. marauna may be endangered by extensive dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
construction in the upper Paraná region.
Taxonomy
Brazilian ichthyologist Mauro Luís Triques described T. marauna in a 1998 volume of the scientific journalScientific journal
In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...
Revue française d'Aquariologie. In 2001, James S. Albert referred this species to a monophyletic group he termed "Apteronotus
Apteronotus
Apteronotus is a genus of weakly electric knifefish in the family Apteronotidae, distinguished by the presence of a tiny caudal fin.-Species:* Black ghost knifefish, Apteronotus albifrons ....
sensu stricto", which placed Tembeassu in synonymy
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
with Apteronotus. However, a subsequent re-examination of the original specimens by Ricardo Campos-da-Paz in 2005 found that this species does not share the derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
characters of Apteronotus; Campos-da-Paz thus returned T. marauna to its own genus
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...
until its phylogenetic relationships can be better investigated.
Distribution and habitat
The three known specimens of T. marauna, two male and one female, were collected from the upper Paraná River at the border between the Brazilian states of Mato Grosso do SulMato Grosso do Sul
Mato Grosso do Sul is one of the states of Brazil.Neighboring Brazilian states are Mato Grosso, Goiás, Minas Gerais, São Paulo and Paraná. It also borders the countries of Paraguay and Bolivia to the west. The economy of the state is largely based on agriculture and cattle-raising...
and São Paulo
São Paulo (state)
São Paulo is a state in Brazil. It is the major industrial and economic powerhouse of the Brazilian economy. Named after Saint Paul, São Paulo has the largest population, industrial complex, and economic production in the country. It is the richest state in Brazil...
in 1965, during the construction of the coffer dam for the Ilha Solteira
Ilha Solteira
Ilha Solteira is a municipality in the state of São Paulo in Brazil. The population in 2004 is 25,168 and the area is 661.34 km². The elevation is 335 m. This city was named after the nearby Ilha Solteira Dam....
reservoir
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...
. These records suggest that this species inhabits deep waters in large rivers.
Description
The largest specimen of T. marauna measures 19.6 cm (7.7 in) long. Like other members of its family, this fish is knife-shaped with a long anal fin extending the length of its body, an electroreceptiveElectroreception
Electroreception is the biological ability to perceive natural electrical stimuli. It has been observed only in aquatic or amphibious animals, since water is a much better conductor than air. Electroreception is used in electrolocation and for electrocommunication.- Overview :Electroreception is...
appendage on its back, and no dorsal
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
or pelvic fins. The head is long and low, with a rounded snout and a straight dorsal profile. The teeth are elongated and conical, numbering around 15 on the premaxillary bone (at the front of the upper jaw) and around 30 on the dentary bone (the lower jaw). The most distinctive feature of T. marauna is a prominent fleshy (possibly cartilaginous) extension at the tip of the upper jaw, in which approximately 15 slender teeth are loosely embedded. Another, toothless, extension is present at the tip of the lower jaw. T. marauna is mostly light brown to gray-brown.
Biology and ecology
Virtually nothing is known of the natural history of T. marauna, including the function of its unique jaw extensions and extra teeth. These structures are found in both sexes, suggesting that they are not involved in reproductive behaviors as in other knifefishes with accessory teeth (e.g. Sternarchogiton nattereriSternarchogiton nattereri
Sternarchogiton nattereri is a species of weakly electric knifefish in the family Apteronotidae. It is native to the Amazon River system and feeds on sponges. Unlike other members of the genus Sternarchogiton, there is pronounced sexual dimorphism in S. nattereri, with reproductively mature males...
). An alternate possibility is that they are used in feeding; similar structures in the stegophiline
Stegophilinae
Stegophilinae is a subfamily of catfishes of the family Trichomycteridae.It includes twelve genera, Acanthopoma, Apomatoceros, Haemomaster, Henonemus, Homodiaetus, Megalocentor, Ochmacanthus, Parastegophilus, Pareiodon, Pseudostegophilus, Schultzichthys, and Stegophilus...
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 are used to gather mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
and scales
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
. In common with other South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
n knifefishes, T. marauna is likely capable of generating a weak electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
for navigation and communication.
Human interactions
The conservation status of T. marauna has not been evaluated by the International Union for Conservation of Nature (IUCN). No new specimens of T. marauna have surfaced in the forty-some years since its initial discovery, during which time its native habitatHabitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
has been extensively altered by dam construction. Thus, this species may be endangered.