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Tenrec

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A tenrec (/ˈtɛnrɛk/) is a mammal belonging to any species within the afrotherian family Tenrecidae, which is endemic to Madagascar.[2] Tenrecs are a very diverse group; as a result of convergent evolution,[3] some resemble hedgehogs, shrews, opossums, rats, and mice. They occupy aquatic, arboreal, terrestrial, and fossorial environments. Some of these species, including the greater hedgehog tenrec, can be found in the Madagascar dry deciduous forests. However, the speciation rate in this group has been higher in humid forests.[4]

Tenrecidae
Temporal range: Bartonian–Recent [1]
Tailless tenrec (Tenrec ecaudatus)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Afrosoricida
Suborder: Tenrecomorpha
Family: Tenrecidae
Gray, 1821
Type genus
Tenrec
Subfamilies
Gray: Tenrecinae ; Blue: Tenrecinae and Oryzorictinae ; Red: Geogalinae and Tenrecinae ; Purple: Geogalinae , Oryzorictinae and Tenrecinae
A taxidermy mount of a tenrec in defensive mode, Horniman Museum and Gardens, London

All tenrecs are believed to descend from a common ancestor that lived 29–37 million years ago[4][5][6] after rafting over from Africa.[7][8] The split from their closest relatives, African otter shrews, is estimated to have occurred about 47–53 million years ago.[4][5][6]

Etymology

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The word tenrec is borrowed, via French,[9] from the Malagasy word tandraka (variant of trandraka[10]), which refers to the tailless tenrec (Tenrec ecaudatus); it has been speculated that the Malagasy word is related to Malay: landak, lit. 'porcupine'.[11]

Evolution

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Tenrecs are believed to have evolved from a single species that colonized Madagascar between 42 and 25 million years ago. The question of how this family reached Madagascar is still unresolved, but the leading hypothesis suggests a small number of individuals may have found themselves on floating vegetation and crossed the Mozambique Channel, which separates Madagascar from southeastern Africa.[2] The Tenrecidae family is one of only four extant terrestrial mammal lineages to have colonized and diversified on Madagascar.[12]

Once established on Madagascar, tenrecs diversified to occupy various niches on the island. Many evolved resemblances to familiar but unrelated mammals that are not found on Madagascar. For instance, the two species of hedgehog tenrec possess coats of hardened spines and the ability to roll into a ball when threatened, characteristics similar to those of true hedgehogs. This example, along with others, demonstrates convergent evolution; it has provided evolutionary biologists with opportunities to study adaptation over evolutionary timescales.[2]

Characteristics

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Tenrecs are small mammals of variable body form. The smallest species are the size of shrews, with a body length of around 4.5 cm (1.8 in), and weighing just 5 g (0.18 oz), while the largest, the common or tailless tenrec, is 25 to 39 cm (9.8 to 15.4 in) in length, and can weigh over 1 kilogram (2.2 lb).[13] Although they may resemble shrews, hedgehogs, or opossums, they are not closely related to any of these groups, their closest relatives being the otter shrews, and after that other African insectivorous mammals including golden moles and elephant shrews. The common ancestry of these animals, which are classified together in the clade Afrotheria, was not recognized until the late 1990s.[14] Continuing work on the molecular[15][16] and morphological[17][18][19][20] diversity of afrotherian mammals has provided ever increasing support for their common ancestry.

Tenrecs are among the few terrestrial mammals that echolocate.[21] Unusual among placental mammals, the rectum and urogenital tracts of tenrecs share a common opening, or cloaca which is a feature more commonly seen in birds, reptiles, and amphibians. They have a low body temperature, sufficiently low that they do not require a scrotum to cool their sperm as do most other mammals.[13][22]

All species appear to be at least somewhat omnivorous, with invertebrates forming the largest part of their diets. One species, Microgale mergulus, is semiaquatic (similar to the lifestyle of their closest relatives, the otter shrews).[23] All of the species, semiaquatic or not, appear to have evolved from a single, common ancestor with the otter shrews comprising the next, most-closely related mammalian species.[24][25] While the fossil record of tenrecs is scarce, at least some specimens from the early Miocene of Kenya show close affinities to living species from Madagascar,[26] such as Geogale aurita.

Most species are nocturnal and have poor eyesight. Their other senses are well developed, however and they have especially sensitive whiskers. As with many of their other features, the dental formula of tenrecs varies greatly between species; they can have from 32 to 42 teeth in total. Unusual for mammals, the permanent dentition in tenrecs tends not to completely erupt until well after adult body size has been reached.[27] This is one of several anatomical features shared by elephants, hyraxes, sengis, and golden moles (but apparently not aardvarks), consistent with their descent from a common ancestor.[citation needed]

Tenrecs have a gestation period of 50 to 64 days, and give birth to a number of relatively undeveloped young. While the otter shrews have just two young per litter, the tailless tenrec can have as many as 32, and females possess up to 29 teats, more than any other mammal.[13] Some tenrec species are social, living in multigenerational family groups with over a dozen individuals.[citation needed]

Interaction with humans

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In the island nation of Mauritius, and also on the Comoran island of Mayotte, some of the inhabitants eat tenrec meat, although it is difficult to obtain (as it is not sold in shops or markets) and difficult to prepare correctly.[citation needed]

The lesser hedgehog tenrec (Echinops telfairi) is one of 16 mammalian species that will have its genome sequenced as part of the Mammalian Genome Project. It is increasingly popular in the pet trade, and in the future may serve as an important model organism in biomedicine, as it is only distantly related to the mice, rats, guinea pigs, and rhesus macaques which comprise the most common research animals.[citation needed]

Threats

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Of the 31 species assessed, 24 (77%) are categorized by the IUCN Red List as Least Concern, 1 species as Data Deficient, 4 species as Vulnerable, and 2 species as Endangered.[28]

The conservation status of many tenrec species is of concern due to an increase of threats within the last 50 years. The main threats facing tenrecs include habitat loss due to deforestation, fragmentation and degradation, hunting, incidental capture, and climate change. Slash-and-burn agriculture, as well as commercial logging and mining of metals is negatively affecting tenrec species that inhabit forests. Five of the six threatened Tenrec species are dependent on forest habitats.[28]

Conservation

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As of 2022, conservation of the tenrec population is not being prioritized. Because most tenrecs are dependent on forest habitats, conservation efforts would need to include a focus on reduction in deforestation on Madagascar as well as habitat restoration.[28] Current conservation efforts include that of the Madagascar Ankizy Fund, started by a paleontological team from Stony Brook University to improve access to health care and education facilities for villagers in remote areas of Madagascar. A healthy and educated local human population will, in the long term, benefit the Malagasy fauna, such as tenrecs.[29]

Species

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See also: List of afrosoricids

The three subfamilies, eight genera, and 31 extant species of tenrecs are[30]

FAMILY TENRECIDAE

See also

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References

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  1. ^ Pickford, Martin (2015). "Late Eocene Potamogalidae and Tenrecidae (Mammalia) from the Sperrgebiet, Namibia" (PDF). Communications of the Geological Survey of Namibia. 16: 114–152.
  2. ^ a b c Olson, Link E. (2013). "Tenrecs". Current Biology. 23 (1): R5–R8. Bibcode:2013CBio...23...R5O. doi:10.1016/j.cub.2012.11.015. PMID 23305671.
  3. ^ Olson, Link E. (2013). "Tenrecs". Current Biology. 23 (1): R5–R8. Bibcode:2013CBio...23...R5O. doi:10.1016/j.cub.2012.11.015. PMID 23305671.
  4. ^ a b c d e Everson, K. M.; Soarimalala, V.; Goodman, S. M.; Olson, L. E. (2016). "Multiple Loci and Complete Taxonomic Sampling Resolve the Phylogeny and Biogeographic History of Tenrecs (Mammalia: Tenrecidae) and Reveal Higher Speciation Rates in Madagascar's Humid Forests". Systematic Biology. 65 (5): 890–909. doi:10.1093/sysbio/syw034. PMID 27103169.
  5. ^ a b Douady, C. J.; Catzeflis, F.; Kao, D. J.; Springer, M. S.; Stanhope, M. J. (2002). "Molecular Evidence for the Monophyly of Tenrecidae (Mammalia) and the Timing of the Colonization of Madagascar by Malagasy Tenrecs". Molecular Phylogenetics and Evolution. 22 (3): 357–363. Bibcode:2002MolPE..22..357D. doi:10.1006/mpev.2001.1055. PMID 11884160.
  6. ^ a b Poux, C.; Madsen, O.; Glos, J.; de Jong, W. W.; Vences, M. (2008). "Molecular phylogeny and divergence times of Malagasy tenrecs: Influence of data partitioning and taxon sampling on dating analyses". BMC Evolutionary Biology. 8 (1): 102. Bibcode:2008BMCEE...8..102P. doi:10.1186/1471-2148-8-102. PMC 2330147. PMID 18377639.
  7. ^ Kinver, M. (2010-01-20). "Mammals 'floated to Madagascar'". BBC News web site. BBC. Retrieved 2010-01-20.
  8. ^ Ali, J. R.; Huber, M. (2010-01-20). "Mammalian biodiversity on Madagascar controlled by ocean currents". Nature. 463 (4 Feb. 2010): 653–656. Bibcode:2010Natur.463..653A. doi:10.1038/nature08706. PMID 20090678. S2CID 4333977.
  9. ^ "tenrec". Merriam-Webster Dictionary. Merriam-Webster. 2021. Retrieved 4 December 2021.
  10. ^ "Rakibolana malagasy sy Rakipahalalana momba an' i Madagasikara : trandraka". mg.mondemalgache.org. Retrieved 2022-06-12.
  11. ^ Blench, Roger; Walsh, Martin (2011), "Faunal names in Malagasy: their etymologies and implications for the prehistory of the East African coast", 11th International Conference on Austronesian Linguistics, Aussois, France, CiteSeerX 10.1.1.467.8453{{citation}}: CS1 maint: location missing publisher (link)
  12. ^ Everson, Kathryn M.; Soarimalala, Voahangy; Goodman, Steven M.; Olson, Link E. (2016-04-21). "Multiple Loci and Complete Taxonomic Sampling Resolve the Phylogeny and Biogeographic History of Tenrecs (Mammalia: Tenrecidae) and Reveal Higher Speciation Rates in Madagascar's Humid Forests". Systematic Biology. 65 (5): 890–909. doi:10.1093/sysbio/syw034. ISSN 1063-5157. PMID 27103169.
  13. ^ a b c Nicholl, Martin (1984). Macdonald, D. (ed.). The Encyclopedia of Mammals. New York: Facts on File. pp. 744–747. ISBN 978-0-87196-871-5.
  14. ^ Stanhope, M.J.; Waddell, V.G.; Madsen, O.; et al. (1998). "Molecular evidence for multiple origins of Insectivora and for a new order of endemic African insectivore mammals". PNAS. 95 (17): 9967–9972. Bibcode:1998PNAS...95.9967S. doi:10.1073/pnas.95.17.9967. PMC 21445. PMID 9707584.
  15. ^ Springer, M.S.; Stanhope, M.J.; Madsen, O.; de Jong, W.W. (2004). "Molecules consolidate the placental mammal tree". Trends Ecol Evol. 19 (8): 430–438. doi:10.1016/j.tree.2004.05.006. PMID 16701301. S2CID 1508898.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  16. ^ Robinson, T. J.; Fu, B.; Ferguson-Smith, M. A.; Yang, F. (2004). "Cross-species chromosome painting in the golden mole and elephant-shrew: support for the mammalian clades Afrotheria and Afroinsectiphillia but not Afroinsectivora". Proceedings of the Royal Society B. 271 (1547): 1477–1484. doi:10.1098/rspb.2004.2754. PMC 1691750. PMID 15306319.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  17. ^ Asher, R.J.; Bennet, N.; Lehmann, T. (2009). "The new framework for understanding placental mammal evolution". BioEssays. 31 (8): 853–864. doi:10.1002/bies.200950053. PMID 19582725. S2CID 46339675.
  18. ^ Tabuce, R.; Marivaux, L.; Adaci, M.; et al. (2007). "Early tertiary mammals from North Africa reinforce the molecular Afrotheria clade". Proceedings of the Royal Society B. 274 (1614): 1159–1166. doi:10.1098/rspb.2006.0229. PMC 2189562. PMID 17329227.
  19. ^ Seiffert, E. (2007). "A new estimate of afrotherian phylogeny based on simultaneous analysis of genomic, morphological, and fossil evidence". BMC Evolutionary Biology. 7 (224): 13. Bibcode:2007BMCEE...7..224S. doi:10.1186/1471-2148-7-224. PMC 2248600. PMID 17999766.
  20. ^ Sanchez-Villagra, M. R., Narita, Y. and Kuratani, S. (2007). "Thoracolumbar vertebral number: the first skeletal synapomorphy for afrotherian mammals". Syst Biodivers. 5 (1): 1–17. Bibcode:2007SyBio...5Q...1S. doi:10.1017/S1477200006002258. S2CID 85675984.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  21. ^ Gould, Edwin (1965). "Evidence for echolocation in the Tenrecidae of Madagascar". Proceedings of the American Philosophical Society. 109 (6): 352–360. JSTOR 986137.
  22. ^ Yin, Steph (29 June 2018). "The Evolutionary Origin of Descending Testicles". The New York Times. Retrieved 2018-07-10.
  23. ^ Benstead, J. P.; Olson, L. E. (2003). "Limnogale mergulus, web-footed tenrec or aquatic tenrec". In S. M. Goodman; J. P. Benstead (eds.). The natural history of Madagascar. Chicago: University of Chicago Press. pp. 1267–1273. ISBN 978-0-226-30307-9.
  24. ^ Olson, L. E.; Goodman, S. M. (2003). "Phylogeny and biogeography of tenrecs". In Goodman, S. M.; Benstead J. P. (eds.). The Natural History of Madagascar. Chicago: Chicago University Press. pp. 1235–1242. ISBN 978-0-226-30307-9.
  25. ^ Poux, C.; Madsen, O.; Glos, J.; de Jong, W.W.; Vences, M. (2008). "Molecular phylogeny and divergence times of Malagasy tenrecs: influence of data partitioning and taxon sampling on dating analyses". BMC Evolutionary Biology. 8 (1): 102. Bibcode:2008BMCEE...8..102P. doi:10.1186/1471-2148-8-102. PMC 2330147. PMID 18377639.
  26. ^ Asher, R.J.; Hofreiter, M. (2006). "Tenrec phylogeny and the noninvasive extraction of nuclear DNA". Systematic Biology. 55 (2): 181–194. doi:10.1080/10635150500433649. PMID 16522569.
  27. ^ Asher, R. J.; Lehmann, T. (2008). "Dental eruption in afrotherian mammals". BMC Biology. 6: 14. doi:10.1186/1741-7007-6-14. PMC 2292681. PMID 18366669.
  28. ^ a b c Stephenson, P. J.; Soarimalala, Voahangy; Goodman, Steven M.; et al. (Jan 2021). "Review of the status and conservation of tenrecs (Mammalia: Afrotheria: Tenrecidae)". Oryx. 55 (1): 13–22. doi:10.1017/S0030605318001205. hdl:20.500.11850/445760. ISSN 0030-6053. S2CID 155184737.
  29. ^ "Afrotherian Conservation | IUCN Afrotheria Specialist Group". www.afrotheria.net. Retrieved 2022-04-23.
  30. ^ Bronner, G.N.; Jenkins, P.D. (2005). "Order Afrosoricida". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. pp. 72–77. ISBN 978-0-8018-8221-0. OCLC 62265494.


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