Plains viscacha rat

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Plains viscacha rat
Tympanoctomys barrerae.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Octodontidae
Genus: Tympanoctomys
Species:
T. barrerae
Binomial name
Tympanoctomys barrerae
(B. Lawrence, 1941) [2]
Tympanoctomys barrerae range.png

The plains viscacha rat, plains vizcacha rat, red viscacha rat, or red vizcacha rat (Tympanoctomys barrerae) is a species of rodent in the family Octodontidae native to Argentina. It is one of three species in the genus Tympanoctomys . [3] [4]

Contents

Description

The plains viscacha rat is a moderately-sized rat, with a large head, long tail, and short ears. Adults measure about 13 cm (5.1 in) in total length, with a 15 cm (5.9 in) tail, and weigh an average of 90 g (3.2 oz), with males being slightly larger than females. The rat has buff-yellow fur with white underparts, fading to dark brown at the tip of the tail. [5]

Distribution and habitat

The plains viscacha rat is endemic to central western Argentina, where it has a fragmented range in Mendoza Province and western La Pampa. Its natural habitat is desert scrubland, dunes and salt flats, between 300 and 1,400 m (980 and 4,590 ft). There are no recognised subspecies. [1] [5]

The species is threatened by destruction of its fragmented and restricted habitat. [1]

Biology and behaviour

Plains viscacha rats are solitary, and nocturnal. They construct complex burrow systems within large artificial mounds. [6] Typical mounds are 13.6 by 8.7 m (45 by 29 ft) across, and 1.25 m (4 ft 1 in) in height, and have an average of 23 burrow entrances. Within the mound, the burrow system has up to three levels and contains numerous chambers and dead-end tunnels. [5]

The rats are herbivorous, feeding primarily on halophytic vegetation, such as Atriplex and Suaeda , [7] although they will occasionally eat other plants such as grass. [5] The rats scrape off and discard salt from the leaves of Atriplex saltbushes with their teeth and bristles around their mouths before eating them. [8] Although this reduces their salt intake, they still produce highly concentrated urine to help maintain their water balance. [9]

The young are born blind, and weighing about 4 g (0.14 oz). Their eyes open at about six days, and they begin to take solid food at ten days. [5]

Genetics

Plains viscacha rat chromosomes Metaphase spread of the Viscacha rat (Tympanoctomys barrerae).jpg
Plains viscacha rat chromosomes

This species of rodent has (as of 2023) the third highest number of chromosomes of any known mammal (2n = 102), [10] behind the tree pangolin (2n = 113/114) [11] and the Bolivian bamboo rat (2n = 118). [12]

It was described as the first known tetraploid (4x = 2n) mammal, thought to have arisen by hybridization and chromosome doubling from an ancestor (very possibly closely related to the mountain vizcacha rat, Octomys mimax, chromosome count 2x = 2n = 56). Some later studies have cast doubt on its tetraploid nature, [13] [14] while others have reasserted it. [15] The doubling of its chromosome number was presumably by errors in mitosis or meiosis within the animal's reproductive organs. [15] A comparison of the chromosomes of the plains viscacha rat and the mountain viscacha rat suggested that the chromosomes of the plains viscacha rat increased relatively rapidly (in evolutionary terms) due to a diverse set of highly repetitive elements. [16] The animal's spermatozoa are roughly twice normal size, thought to be by virtue of having twice as many sets of chromosomes. [17]

The rodent is not a rat, but a caviomorph, kin to guinea pigs and chinchillas.

Related Research Articles

<span class="mw-page-title-main">Ploidy</span> Number of sets of chromosomes in a cell

Ploidy is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively, in each homologous chromosome pair, which chromosomes naturally exist as. Somatic cells, tissues, and individual organisms can be described according to the number of sets of chromosomes present : monoploid, diploid, triploid, tetraploid, pentaploid, hexaploid, heptaploid or septaploid, etc. The generic term polyploid is often used to describe cells with three or more sets of chromosomes.

<span class="mw-page-title-main">Polyploidy</span> Condition where cells of an organism have more than two paired sets of chromosomes

Polyploidy is a condition in which the cells of an organism have more than one pair of (homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one from each of two parents; each set contains the same number of chromosomes, and the chromosomes are joined in pairs of homologous chromosomes. However, some organisms are polyploid. Polyploidy is especially common in plants. Most eukaryotes have diploid somatic cells, but produce haploid gametes by meiosis. A monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid. Males of bees and other Hymenoptera, for example, are monoploid. Unlike animals, plants and multicellular algae have life cycles with two alternating multicellular generations. The gametophyte generation is haploid, and produces gametes by mitosis; the sporophyte generation is diploid and produces spores by meiosis.

<span class="mw-page-title-main">Viscacha</span> Group of rodents

Viscacha or vizcacha are rare rodents of two genera in the family Chinchillidae. They are native to South America and convergently resemble rabbits.

Kirchner, a surname of German origin, from the Middle High German word, 'kirchenaere'. Kirchner originated as an occupational surname for a church worker, such as a priest, church assistant or a church property administrator. Notable people with the name include:

The golden viscacha rat or golden vizcacha rat is the single species of the genus Pipanacoctomys of the rodent family Octodontidae. It has 92 chromosomes and has been regarded as tetraploid. This octodontid and its sister-species, the plains viscacha rat, may have arisen from the diploid mountain viscacha rat, as a result of the doubling and subsequent loss of some chromosomes. However, some genetic studies have rejected any polyploidism in mammals as unlikely, and suggest that amplification and dispersion of repetitive sequences best explain the large genome size.

The aquatic rat, Ecuador fish-eating rat, fish-eating rat or Ecuadoran ichthyomyine is a South American species of semiaquatic rodent in the family Cricetidae. It is the only species in the genus Anotomys. This species is currently considered endangered. It is thought to be nocturnal and feeds on aquatic arthropods and insects. It is found in small ranges along the Andes.

Pittier's crab-eating rat is a species of semiaquatic rodent in the family Cricetidae. It is endemic to Venezuela. The natural habitats of this species are rivers and swamps. Its karyotype has 2n = 92 and FNa = 98. This was previously thought to be the highest chromosome number known for a mammal, but it has since been found that the plains viscacha rat or red viscacha rat has 4x = 2n = 102.

<span class="mw-page-title-main">Plains viscacha</span> Species of rodent

The plains viscacha or plains vizcacha is a species of viscacha, a rodent in the family Chinchillidae. It is the only living species within the genus Lagostomus. It is found in Argentina, Bolivia, and Paraguay. The plains viscacha is the largest species in its family. They construct elaborate burrows that house successive colonies for decades.

The mountain viscacha rat or mountain vizcacha rat, historically viscacha rat or vizcacha rat, is a species of rodent in the family Octodontidae. It is endemic to Argentina.

<i>Tympanoctomys</i> Genus of rodents

Tympanoctomys is a genus of rodent in the family Octodontidae. There are three extant species in the genus: T. barrerae, T. kirchnerorum and T. loschalchalerosorum. T. loschalchalerosorum was formerly considered to be monotypic within the genus Salinoctomys, but has been shown by genetic analysis to nest within the variation of T. barrerae.

Viscacha rats are a group of rodents in the family Octodontidae. All species are found in Argentina. They are placed in the following genera:

<span class="mw-page-title-main">Octodontidae</span> Family of rodents

Octodontidae is a family of rodents, restricted to southwestern South America. Fourteen species of octodontid are recognised, arranged in seven genera. The best known species is the common degu, Octodon degus.

The Chalchalero viscacha rat or Chalchalero vizcacha rat is a species of caviomorph rodent in the family Octodontidae. It was formerly considered to be monotypic within the genus Salinoctomys, but has been shown by genetic analysis to nest within Tympanoctomys, and in particular, within the variation of T. barrerae. The species is endemic to a small area of northwestern Argentina, where it lives in shrublands bordering the salt flats of the Salinas Grandes. Its diet consists of halophyte plants. It is named after an Argentine musical group, Los Chalchaleros, whose songs were popular with its discoverers.

Bridges's degu is a species of rodent in the family Octodontidae. It is found in southern Chile. The species was named after Thomas Bridges.

The 2000s witnessed an explosion of genome sequencing and mapping in evolutionarily diverse species. While full genome sequencing of mammals is rapidly progressing, the ability to assemble and align orthologous whole chromosomal regions from more than a few species is not yet possible. The intense focus on the building of comparative maps for domestic, laboratory and agricultural (cattle) animals has traditionally been used to understand the underlying basis of disease-related and healthy phenotypes.

Kirchner's viscacha rat or Kirchner's vizcacha rat is a species of rodent in the family Octodontidae described in 2014. It is one of three species in the genus Tympanoctomys. That species is endemic to Chubut Province in the central western Argentina, where it has a fragmented range. Its natural habitat is desert scrubland, dunes and salt flats, where it eats halophyte plants. It is a solitary, nocturnal rodent that constructs large mounds with complex burrows. The species was named in honor of both Cristina Fernández de Kirchner and Néstor Kirchner, presidents of Argentina.

<span class="mw-page-title-main">High Monte</span>

The High Monte is a montane grasslands and shrublands ecoregion in Argentina.

<span class="mw-page-title-main">Michael A. Mares</span> American zoologist, academic, and author

Michael A. Mares is an American zoologist, academic, and author. He is the Emeritus Director and Curator at the Sam Noble Museum, as well as a Professor Emeritus in the Department of Biology at the University of Oklahoma.

References

  1. 1 2 3 Roach, N. (2016). "Tympanoctomys barrerae". IUCN Red List of Threatened Species . 2016: e.T22586A78323698. doi: 10.2305/IUCN.UK.2016-2.RLTS.T22586A78323698.en . Retrieved 12 November 2021.
  2. ↑ Lawrence, B. (1941), "A new species of Octomys from Argentina", Proceedings of the New England Zoological Club, 18: 43–46
  3. ↑ Woods, C.A.; Kilpatrick, C.W. (2005). "Infraorder Hystricognathi". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 1573. ISBN   978-0-8018-8221-0. OCLC   62265494.
  4. ↑ Pablo Teta; Ulyses F. J. Pardiñas; Daniel E. Udrizar Sauthier i Milton H. Gallardo (2014), "A new species of the tetraploid vizcacha rat Tympanoctomys (Caviomorpha, Octodontidae) from central Patagonia, Argentina", Journal of Mammalogy , 95 (1): 60–71, doi: 10.1644/13-MAMM-A-160
  5. 1 2 3 4 5 Diaz, G.B.; et al. (2000). "Tympanoctomys barrerae" (PDF). Mammalian Species. 646: 1–4. doi:10.1644/1545-1410(2000)646<1:tb>2.0.co;2. Archived from the original (PDF) on 2016-03-04. Retrieved 2015-07-11.
  6. ↑ Mares, Michael A. (1 November 2003). "Desert dreams: seeking the secret mammals of the salt pans - Naturalist at Large" (PDF). Natural History : 29–34.
  7. ↑ Torres-Mura, J.C. (1989). "Herbivorous specialization of the South American desert rodent Tympanoctomys barrerae". Journal of Mammalogy. 70 (3): 646–648. doi:10.2307/1381442. JSTOR   1381442.
  8. ↑ Mares, M.A.; et al. (1997). "How desert rodents overcome halophytic plant defenses". BioScience. 47 (11): 699–704. doi:10.2307/1313210. JSTOR   1313210.
  9. ↑ Diaz, G.B. & Ojeda R.A. (1999). "Kidney structure and allometry of Argentine desert rodents". Journal of Arid Environments. 41 (4): 453–461. Bibcode:1999JArEn..41..453D. doi:10.1006/jare.1998.0472.
  10. ↑ Evans, Ben J.; Upham, Nathan S.; Golding, Brian G.; Ojeda, Ricardo A.; Ojeda, Agustina A. (2017). "Evolution of the largest mammalian genome". Genome Biology and Evolution. 9 (6): 1711–1724. doi:10.1093/gbe/evx113. PMC   5569995 . PMID   28854639.
  11. ↑ Houck, Marlys L.; Koepfli, Klaus-Peter; Hains, Taylor; Khan, Ruqayya; Charter, Suellen J.; Fronczek, Julie A.; Misuraca, Ann C.; Kliver, Sergei; Perelman, Polina L.; Beklemisheva, Violetta; Graphodatsky, Alexander; Luo, Shu-Jin; O’Brien, Stephen J.; Lim, Norman T.-L.; Chin, Jason S. C. (2023-04-12). "Chromosome-length genome assemblies and cytogenomic analyses of pangolins reveal remarkable chromosome counts and plasticity". Chromosome Research. 31 (2): 13. doi:10.1007/s10577-023-09722-y. ISSN   1573-6849.
  12. ↑ Dunnam, J. L.; Salazar-Bravo, J.; Yates, T. L. (2001). "The Bolivian Bamboo Rat, Dactylomys boliviensis (Rodentia: Echimyidae), a new record for chromosome number in a mammal". Mammalian Biology. 66 (2): 121–126 – via Springer.
  13. ↑ Svartman, Marta; Stone, Gary; Stanyon, Roscoe (2005). "Molecular cytogenetics discards polyploidy in mammals". Genomics. 85 (4): 425–30. doi:10.1016/j.ygeno.2004.12.004. PMID   15780745.
  14. ↑ Graphodatsky, Alexander S.; Trifonov, Vladimir A.; Stanyon, Roscoe (12 October 2011). "The genome diversity and karyotype evolution of mammals". Molecular Cytogenetics. 4 (1): 22. doi: 10.1186/1755-8166-4-22 .
  15. 1 2 Gallardo, M.H.; González, CA; Cebrián, I (2006), "Molecular cytogenetics and allotetraploidy in the red vizcacha rat, Tympanoctomys barrerae (Rodentia, Octodontidae)", Genomics (published August 2006), vol. 88, no. 2, pp. 214–221, doi: 10.1016/j.ygeno.2006.02.010 , PMID   16580173
  16. ↑ "New analysis of rare Argentinian rat unlocks origin of the largest mammalian genome". PhysOrg. 2017-07-12. Retrieved 2017-07-17.
  17. ↑ Gallardo, M.H.; et al. (1999). "Discovery of tetraploidy in a mammal". Nature. 401 (6751): 341. Bibcode:1999Natur.401..341G. doi: 10.1038/43815 . PMID   10517628. S2CID   1808633.
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