Atretochoana

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Atretochoana
Atretochoana eiselti.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Gymnophiona
Clade: Apoda
Family: Typhlonectidae
Genus: Atretochoana
Nussbaum and Wilkinson, 1995
Species:
A. eiselti
Binomial name
Atretochoana eiselti
(Taylor, 1968)
Atretochoana eiselti Range.jpg

Atretochoana eiselti is a species of caecilian originally known only from two preserved specimens discovered by Sir Graham Hales in the Brazilian rainforest, while on an expedition with Sir Brian Doll in the late 1800s, but rediscovered in 2011 by engineers working on a hydroelectric dam project in Brazil. Until 1998, it was known only from the type specimen in the Naturhistorisches Museum, Vienna. [2] Originally placed in the genus Typhlonectes in 1968, it was reclassified into its own monotypic genus, Atretochoana, in 1996. It was also found to be more closely related to the genus Potamotyphlus than Typholonectes. [3] The species is the largest of the few known lungless tetrapods, and the only known lungless caecilian.

Contents

Description

A. eiselti is the largest tetrapod to lack lungs, double the size of the next largest. [4] Caecilians such as Atretochoana are limbless amphibians with snake-like bodies, marked with rings like those of earthworms. [5] It has significant morphological differences from other caecilians, even the genera most closely related to it, even though those genera are aquatic. [3] The skull is very different from those of other caecilians, giving the animal a broad, flat head. [4] Its nostrils are sealed, [3] and it has an enlarged mouth with a mobile cheek. [6] Its body has a fleshy dorsal fin. [4]

Most caecilians have a well-developed right lung and a vestigial left lung. Some, such as Atretochoana's relatives, have two well-developed lungs. Atretochoana, however, entirely lacks lungs, and has a number of other features associated with lunglessness, including sealed choanae, and an absence of pulmonary arteries. [7] Its skin is filled with capillaries that penetrate the epidermis, allowing gas exchange. Its skull shows evidence of muscles not found in any other organism. [6] The Vienna specimen of Atretochoana is a large caecilian at a length of 72.5 cm (28.5 in), [7] while the Brasília specimen is larger still at 80.5 cm (31.7 in). [8] By comparison, caecilians in general range in length from 11 to 160 cm (4.3 to 63.0 in). [7]

Although it is not a snake, it has been called various common names in the media such as "penis snake", "man-aconda", and "floppy snake", owing to its visual similarity to the human penis. [9] [10]

History

The specimen in the Vienna museum was known only to have originated from somewhere in South America, at least before 1945, most likely in the 19th century. [11] Its lack of lungs was not known at this time, and the specimen was assigned to the species Typhlonectes compressicauda . [12] The Vienna specimen was the holotype for this species when it was first described by Edward Harrison Taylor in his 1968 monograph Caecilians of the World. He named it Typhlonectes eiselti, in honour of Viennese herpetologist Josef Eiselt. [13] Taylor considered it to be similar to the aquatic caecilians of the genus Typhlonectes and Potamotyphlus , and placed it in the former genus, taking much note only of its large size and high number of splenial teeth. [12]

Taylor did not inform the curators of the Naturhistorisches Museum that he designated the specimen a holotype, so it was not mentioned in the museum's catalogue of type specimens, and was placed beneath glass in a public display. There, it was noticed by the visiting English herpetologist Mark Wilkinson, who then borrowed the specimen to examine it with his American colleague Ronald A. Nussbaum. Examination of the specimen showed it to have a number of unusual features, including the large number of splenial teeth observed by Taylor, but most unusually, closed choanae, which showed it could not fill any lungs it might have. [12]

Because of these and other distinctive features, Nussbaum and Wilkinson gave this species its own genus when they reported on the results of their research in a 1995 issue of the Proceedings of the Royal Society B . The name they gave this genus was Atretochoana, from the Greek word atretos, meaning "imperforate", and the Greek word choana, referring to a funnel or tube. [7] Nussbaum and Wilkinson published further studies in 1997 describing in detail the caecilian's anatomy and morphology. In 1998, they discovered the second specimen in the University of Brasília, [14] although the origin of this specimen was also unknown. [1] In 1999, they determined Atretochoana was a sister taxon of Potamotyphlus, and in 2011, grouped it in the family Typhlonectidae. [14] Both of these specimens are mature females. [11]

Biology

Most caecilians are burrowers, but some, including Atretochoana's relatives, are largely aquatic. [12] Atretochoana is thought to be aquatic since its relatives and lungless salamanders, some of the few other lungless tetrapods, are aquatic as well. [13] It was postulated to inhabit fast-flowing water. [6]

Due to the lack of information, it is classified as Data Deficient by the International Union for Conservation of Nature. It is thought to be uncommon, with a limited distribution. [2] It is likely a predator or scavenger, [6] and is thought to be viviparous. [1]

In June 2011, an amphibian was photographed near Praia de Marahú on the island of Mosqueiro (near Belém, Brazil) that appeared to be A. eiselti, but was not positively identified. In 2011, six individual organisms were found in the Madeira River. Neither have cold, fast-flowing water, as was originally thought, as there is less oxygen in warmer water. This makes its lack of lungs even more unusual, and the question of how it breathes has not yet been resolved. [14] [15] [16]

Related Research Articles

<span class="mw-page-title-main">Caecilian</span> Order of amphibians

Caecilians are a group of limbless, vermiform (worm-shaped) or serpentine (snake-shaped) amphibians with small or sometimes nonexistent eyes. They mostly live hidden in soil or in streambeds, and this cryptic lifestyle renders caecilians among the least familiar amphibians. Modern caecilians live in the tropics of South and Central America, Africa, and southern Asia. Caecilians feed on small subterranean creatures such as earthworms. The body is cylindrical and often darkly coloured, and the skull is bullet-shaped and strongly built. Caecilian heads have several unique adaptations, including fused cranial and jaw bones, a two-part system of jaw muscles, and a chemosensory tentacle in front of the eye. The skin is slimy and bears ringlike markings or grooves and may contain scales.

<span class="mw-page-title-main">Rhinatrematidae</span> Family of amphibians

Rhinatrematidae is a family of caecilians, also known as the Neotropical tailed caecilians, American tailed caecilians. or beaked caecilians. They are found in the equatorial countries of South America.

<i>Uraeotyphlus</i> Genus of amphibians

Uraeotyphlus is a genus of caecilians in the family Ichthyophiidae. There are seven species in this genus, all of which are endemic to the Western Ghats of southwestern India. Previously, the genus has also been placed in its own monotypic family Uraeotyphlidae.

<span class="mw-page-title-main">Scolecomorphidae</span> Family of amphibians

The Scolecomorphidae are a family of caecilians also known as tropical caecilians, buried-eyed caecilians, or African caecilians. They are found in Cameroon in West Africa, and Malawi and Tanzania in East Africa. Caecilians are legless amphibians which superficially resemble worms or snakes.

<span class="mw-page-title-main">Caeciliidae</span> Family of amphibians

Caeciliidae is the family of common caecilians. They are found in Central and South America. Like other caecilians, they superficially resemble worms or snakes.

<span class="mw-page-title-main">Typhlonectidae</span> Family of amphibians

Typhlonectidae, also known as aquatic caecilians or rubber eels, are a family of caecilians found east of the Andes in South America.

<span class="mw-page-title-main">Caecilians of the Western Ghats</span>

The Western Ghats in India are home to several species of caecilians (Gymnophiona). Caecilians are legless, burrowing amphibians which mostly live in leaf litter, loose soil, under rocks and decaying logs. They are also found in agricultural fields and only surface during the monsoon. The body is elongated and smooth with a slimy skin. The smaller caecilians superficially resemble earthworms while the larger ones are often mistaken for snakes. However, they can be told apart from earthworms by the presence of eyes, teeth and skeleton and from snakes by the lack of scales on skin. The eyes in caecilians are not well developed which is most likely to be because of their burrowing life style. They are considered as rare which is apparently due to their subterranean habits. To see them one has to search carefully and be at the right place and at the right time. There are few places where they are common, but, at least one species was reported to be abundant in agricultural fields in Kerala. The larger caecilians can resemble snakes, but their skin is smooth, not scaly.

Brasilotyphlus is a genus of caecilians in the family Siphonopidae. It was considered monotypic, containing only the species Brasilotyphlus braziliensis. However, two recently described species, Brasilotyphlus guarantanus and Brasilotyphlus dubium, have been placed in this same genus. All three species are endemic to Brazil. This genus has also been suggested as paraphyletic to Microcaecilia.

<i>Chthonerpeton exile</i> Species of amphibian

Chthonerpeton exile is a species of caecilian in the family Typhlonectidae. It is endemic to Brazil, and only known from its imprecise type locality "Bahia". Only one specimen is known and now lost. The specific name exile, form Latin exilis, refers to the "relatively slender, delicate shape of the body and head." The common name Bahia caecilian has been coined for this species.

<i>Chthonerpeton indistinctum</i> Species of amphibian

Chthonerpeton indistinctum is a species of caecilian in the family Typhlonectidae. It is found in northeastern Argentina, Paraguay, Uruguay, and southeastern Brazil. The common name Argentine caecilian has been coined for it.

Chthonerpeton perissodus is a species of caecilian in the family Typhlonectidae. It is endemic to Minas Gerais, Brazil, and only known from its imprecise type locality, Rio Pandeiro. Only three specimens are known. The common name Minas Gerais caecilian has been coined for this species.

<i>Microcaecilia</i> Genus of amphibians

Microcaecilia is a genus of caecilians in the family Siphonopidae.

Mimosiphonops is a genus of caecilians in the family Siphonopidae. The genus is definitely known only from the state of Rio de Janeiro, Brazil. They are sometimes known as the worm patterned caecilians.

<i>Potamotyphlus kaupii</i> Genus of amphibians

Potamotyphlus kaupii is a species of amphibian in the family Typhlonectidae. It is monotypic within the genus Potamotyphlus. It is found widely in the Amazon Basin and the Guianas in South America, and is known to occur in Brazil, Colombia, Ecuador, Peru, Venezuela, and possibly Bolivia. It is an entirely aquatic species and typically ranges between 30 and 60 cm (12–24 in) in length.

<i>Schistometopum thomense</i> Species of amphibian

Schistometopum thomense is a species of amphibian in the family Dermophiidae, endemic to São Tomé and Ilhéu das Rolas. It is found in most soils on São Tomé, from tropical moist lowland forests to coastal coconut plantations. It is absent only from the driest northern areas of the island. It is typically around 30 cm (12 in) in length, and is often bright yellow. The size of S. thomense can vary throughout São Tomé, however, and it is the only known caecilian to follow Bergmann's rule, which states that a decreasing temperature due to factors such as increasing altitude will cause an increase in the body size of endothermic vertebrate species. The island of São Tomé is a massive shield volcano, and it therefore has differing altitudes throughout the island, potentially resulting in the size diversity of S. thomense. This species may be referred to as the São Tomé caecilian, as the Agua Ize caecilian, or as the island caecilian, or by the local name of cobra bobo.

<i>Typhlonectes compressicauda</i> Species of amphibian

Typhlonectes compressicauda, the Cayenne caecilian, is a species of amphibian in the family Typhlonectidae that lives in water. It is found in Amazonian Brazil, Peru, and Colombia as well as in Guyana and French Guiana, and likely Suriname, and according to some sources, Venezuela. It is an aquatic caecilian that inhabits permanent rivers and marshes mainly in the lowland forest zone.

Indotyphlus is a small genus of caecilians in the family Grandisoniidae. As caecilians in general, they superficially resemble earthworms. The genus is endemic to the Western Ghats, India. They are sometimes known as Battersby's caecilians.

Microcaecilia iwokramae is a species of caecilian in the family Siphonopidae. It is endemic to Guyana and only known from its type locality in the Iwokrama Forest. It was first described as Caecilita iwokramae in the monotypic genus Caecilita, before being recognised as belonging to Microcaecilia.

<span class="mw-page-title-main">Siphonopidae</span> Family of amphibians

The Siphonopidae are the family of common caecilians. They are found in Central and South America. Like other caecilians, they superficially resemble worms or snakes.

<span class="mw-page-title-main">Mosqueiro</span> Island in Pará State, Brazil

Mosqueiro is an island near the south bank of the Pará River in the Brazilian state of Pará. Since July 6, 1989, the northwest coast of the island has comprised an administrative district of the city of Belém, roughly 67 km (42 mi) north of the downtown area of the city. The island has 17 km (11 mi) of beaches with freshwater tides, which draw vacationers primarily in the dry season. The largest settlement on the island is the town of Vila on the westernmost part of the island.

References

  1. 1 2 3 Mark Wilkinson, John Measey, Marvalee Wake (2004). "Atretochoana eiselti". IUCN Red List of Threatened Species . 2004: e.T59493A11937533. doi: 10.2305/IUCN.UK.2004.RLTS.T59493A11937533.en . Retrieved 17 November 2021.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. 1 2 "Distribution and conservation". Natural History Museum. Retrieved 22 February 2012.
  3. 1 2 3 "Taxonomy". Natural History Museum. Retrieved 22 February 2012.
  4. 1 2 3 "Atretochoana eiselti". Natural History Museum. Retrieved 22 February 2012.
  5. ↑ Naskrecki, Piotr (2005). The Smaller Majority . London: Belknap. pp.  46–47. ISBN   978-0-647-02562-8.
  6. 1 2 3 4 "Biology". Natural History Museum. Retrieved 22 February 2012.
  7. 1 2 3 4 Nussbaum, Ronald A.; Wilkinson, Mark (1995). "A New Genus of Lungless Tetrapod: A Radically Divergent Caecilian (Amphibia: Gymnophiona)". Proceedings of the Royal Society B . 261 (1362): 331–339. Bibcode:1995RSPSB.261..331N. doi:10.1098/rspb.1995.0155. S2CID   84351569.
  8. ↑ Wilkinson, M.; Sebben, A.; Schwartz, E.N.F.; Schwartz, C.A. (1998). "The largest lungless tetrapod: report on a second specimen of Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae) from Brazil" (PDF). Journal of Natural History. 32 (4): 617–627. doi:10.1080/00222939800770321.
  9. ↑ "Penis Snake is neither penis nor snake, but looks like both". 4 August 2012.
  10. ↑ "'Penis snake' discovered in Brazil is actually a rare species of amphibian". August 2012.
  11. 1 2 Knapp, Michelle (3 February 2003). "Atretochoana eiselti". Information on amphibian biology and conservation. AmphibiaWeb. Retrieved 21 January 2010.
  12. 1 2 3 4 Nussbaum, Ronald A.; Wilkinson, Mark (1997). "Comparative morphology and evolution of the lungless caecilian Atretochoana eiselti (Taylor) (Amphibia: Gymnophiona: Typhlonectidae)" (PDF). Biological Journal of the Linnean Society. 62 (1): 39–109. doi: 10.1111/j.1095-8312.1997.tb01616.x .
  13. 1 2 Himstedt, Werner (2000). "Lungless Tetradodes". In Hofrichter, Robert (ed.). Amphibians: The World of Frogs, Toads, Salamanders and Newts. New York: Firefly. p.  81. ISBN   1-55209-541-X.
  14. 1 2 3 Hoogmoed, Marinus Steven; Maciel, Adriano Oliveira; Coragem, Juliano Tupan (2011). "Discovery of the largest lungless tetrapod, Atretochoana eiselti (Taylor, 1968) (Amphibia: Gymnophiona: Typhlonectidae), in its natural habitat in Brazilian Amazonia" (PDF). Boletim do Museu Paraense Emílio Goeldi - Ciências Naturais. 6 (3): 241–262. doi:10.46357/bcnaturais.v6i3.608. ISSN   1981-8114. S2CID   83940114. Archived from the original (PDF) on 13 August 2012. Retrieved 22 February 2011.
  15. ↑ Ximenes, Marcela (31 July 2012). "Anfíbio com formato de cobra é descoberto no Rio Madeira, em RO" [Snake-shaped amphibian found in the Rio Madeira, RO] (in Portuguese). Globo. Archived from the original on 3 August 2012. Retrieved 1 August 2012.
  16. ↑ Butler, Rhett (2 August 2012). "'Penis snake' discovered in Brazil is actually a rare species of amphibian". Mongabay. Retrieved 11 August 2013.
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