Tenrec

A tenrec is any species of mammal within the afrotherian family Tenrecidae endemic to Madagascar.[2] Tenrecs are widely diverse; as a result of convergent evolution[3] some resemble hedgehogs, shrews, opossums, rats and/or 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]

For the species, see Tailless tenrec.

Tenrecidae
Temporal range: Bartonian–Recent [1]
Tailless tenrec (Tenrec ecaudatus)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Afrosoricida
Suborder: Tenrecomorpha
Family: Tenrecidae
Gray, 1821
Subfamilies
A taxidermy 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 (Ma) 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 Ma ago.[4][5][6]

Characteristics

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).[9] Although they may resemble shrews, hedgehogs, or opposums, they are not closely related to any of these groups, their closest relatives being the otter shrews, and after that, other African insectivorous mammals, such as golden moles and elephant shrews. The common ancestry of these animals, along with aardvarks, hyraxes, elephants, and sea cows in the group Afrotheria, was not recognized until the late 1990s.[10] Continuing work on the molecular[11][12] and morphological[13][14][15][16] diversity of afrotherian mammals has provided ever increasing support for their common ancestry.

Unusually among placental mammals, the anus and urogenital tracts of tenrecs share a common opening, or cloaca, a feature more commonly seen in birds, reptiles, and amphibians. They have a low body temperature, sufficiently so that they do not require a scrotum to cool their sperm as do most other mammals.[9][17]

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).[18] 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.[19][20] 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,[21] 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.[22] 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.

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.[9] At least some tenrec species are social, living in multigenerational family groups with over a dozen individuals.

Interaction with humans

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

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 that comprise the most common research animals.

Species

The three subfamilies, 8 genera, and 31 extant species of tenrecs are:[23]

FAMILY TENRECIDAE

See also

References
  1. Martin Pickford (2015). "Late Eocene Potamogalidae and Tenrecidae (Mammalia) from the Sperrgebiet, Namibia" (PDF). Communications of the Geological Survey of Namibia. 16: 114–152.
  2. Olson, Link E. (2013). "Tenrecs". Current Biology. 23 (1): R5–R8. doi:10.1016/j.cub.2012.11.015. PMID 23305671.
  3. Olson, Link E (2013). "Tenrecs". Current Biology. 23 (1): R5–R8. doi:10.1016/j.cub.2012.11.015. PMID 23305671.
  4. 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. 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. doi:10.1006/mpev.2001.1055. PMID 11884160.
  6. 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. 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. Nicholl, Martin (1984). Macdonald, D. (ed.). The Encyclopedia of Mammals. New York: Facts on File. pp. 744–747. ISBN 978-0-87196-871-5.
  10. Stanhope, MJ; Waddell, VG; Madsen, O; de Jong, W; Hedges, SB; Cleven, GC; Kao, D; Springer, MS (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.
  11. Springer MS, Stanhope MJ, Madsen O, de Jong WW (2004). "Molecules consolidate the placental mammal tree". Trends Ecol Evol. 19 (8): 430–438. doi:10.1016/j.tree.2004.05.006. PMID 16701301.
  12. 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.CS1 maint: multiple names: authors list (link)
  13. Asher RJ; Bennet N; Lehmann T. (2009). "The new framework for understanding placental mammal evolution". BioEssays. 31 (8): 853–864. doi:10.1002/bies.200900053. PMID 19582725. S2CID 46339675.
  14. Tabuce, R.; Marivaux, L.; Adaci, M.; Bensalah, M.; Hartenberger, J.-L.; Mahboubi, M.; Mebrouk, F.; Tafforeau, P.; Jaeger, J.-J. (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.
  15. Seiffert, E. (2007). "A new estimate of afrotherian phylogeny based on simultaneous analysis of genomic, morphological, and fossil evidence". BMC Evol Biol. 7 (224): 13. doi:10.1186/1471-2148-7-224. PMC 2248600. PMID 17999766.
  16. 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. doi:10.1017/S1477200006002258. S2CID 85675984.CS1 maint: multiple names: authors list (link)
  17. "The Evolutionary Origin of Descending Testicles". Retrieved 2018-07-10.
  18. Benstead, J. P.; L. E. Olson (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.
  19. Olson LE, Goodman SM (2003). "Phylogeny and biogeography of tenrecs". In Goodman SM, Benstead JP (eds.). The Natural History of Madagascar. Chicago: Chicago University Press. pp. 1235–1242. ISBN 978-0-226-30307-9.
  20. Poux C; Madsen O; Glos J; de Jong WW; Vences M. (2008). "Molecular phylogeny and divergence times of Malagasy tenrecs: influence of data partitioning and taxon sampling on dating analyses". BMC Evol Biol. 8: 102. doi:10.1186/1471-2148-8-102. PMC 2330147. PMID 18377639.
  21. Asher RJ, Hofreiter M (2006). "Tenrec phylogeny and the noninvasive extraction of nuclear DNA". Syst Biol. 55 (2): 181–194. doi:10.1080/10635150500433649. PMID 16522569.
  22. Asher, R. J.; Lehmann, T. (2008). "Dental eruption in afrotherian mammals". BMC Biol. 6: 14. doi:10.1186/1741-7007-6-14. PMC 2292681. PMID 18366669.
  23. 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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