Tenrecidae

Tenrecidae
Temporal range: Early Miocene–Recent
[1]
Tenrec ecaudatus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Afrosoricida
Suborder: Tenrecomorpha
Butler, 1972
Family: Tenrecidae
Gray, 1821
Subfamilies

Tenrecidae (common name tenrecs) is a family of mammals found on Madagascar and parts of Africa. Tenrecs are widely diverse, resembling hedgehogs, shrews, opossums, mice and even otters, as a result of convergent evolution. They occupy aquatic, arboreal, terrestrial and fossorial environments. Some of these species can be found in the Madagascar dry deciduous forests, including the Greater Hedgehog Tenrec.

Contents

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 centimetres (1.8 in), and weighing just 5 grams (0.18 oz), while the largest, the Common Tenrec, is 25 to 39 centimetres (9.8 to 15 in) in length, and can weigh over 1 kilogram (2.2 lb).[2] Although they may resemble such animals as shrews, hedgehogs, or otters, they are not closely related to any of these groups, their closest relatives being other African, insectivoran-grade 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.[3] Continuing work on the molecular[4][5] and morphological[6][7][8][9] 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 most other mammals do.[2]

All species appear to be at least somewhat omnivorous, with invertebrates forming the largest part of the diet. The three species found on the African mainland (Potamogale velox, Micropotamogale lamottei, M. ruwenzorii) have a more specialized diet, centered on their habitat in fast-running streams of the African tropics, from Liberia in the west to Lake Victoria in the east. One species from Madagascar, Limnogale mergulus, is also semiaquatic.[10] All of the species from Madagascar, semiaquatic or not, appear to have evolved from a single, common ancestor, with the mainland tenrecs comprising the next, most-closely related mammalian species.[11][12] 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,[13] 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 anything from 32 to 42 teeth in total. Unusually for mammals, the permanent dentition in tenrecs tends not to completely erupt until well after adult body size has been reached.[14] 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 from 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 Common Tenrec can have as many as 32, and females possess up to 29 teats, more than any other mammal.[2] At least some species of tenrec are social, living in multi-generational family groups with over a dozen individuals.

Use

In the island nation of Mauritius, some of the inhabitants eat tenrec meat even 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

There are four subfamilies, 10 genera, and 34 species of tenrecs.

FAMILY TENRECIDAE

See also

References

  1. ^ Savage, RJG, & Long, MR (1986). Mammal Evolution: an illustrated guide. New York: Facts on File. pp. 53. ISBN 0-8160-1194-X. 
  2. ^ a b c Nicholl, Martin (1984). Macdonald, D.. ed. The Encyclopedia of Mammals. New York: Facts on File. pp. 744–747. ISBN 0-87196-871-1. 
  3. ^ Stanhope, M.J. et al. (1998) Molecular evidence for multiple origins of Insectivora and for a new order of endemic African insectivore mammals. Proc. Natl. Acad. Sci. U. S. A. 95, 9967–9972
  4. ^ Springer MS, Stanhope MJ, Madsen O, de Jong WW: Molecules consolidate the placental mammal tree. Trends Ecol Evol 2004, 19(8):430-438.
  5. ^ 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- ROYAL SOCIETY OF LONDON B. 271(1547): 1477-1484
  6. ^ Asher RJ, Bennet N, Lehmann T. 2009. The new framework for understanding placental mammal evolution. BioEssays 31:853–864
  7. ^ Tabuce, R., Marivaux, L., Adaci,M., Bensalah,M., Hartenberger, J. L., et al. Early tertiary mammals from north Africa reinforce the molecular afrotheria clade. Proc Royal Soc B-Biol Sci 2007. 274: 1159–1166.
  8. ^ Seiffert, E., A new estimate of afrotherian phylogeny based on simultaneous analysis of genomic, morphological, and fossil evidence. BMC Evol Biol 2007. 7: 13.
  9. ^ Sanchez-Villagra, M. R., Narita, Y. and Kuratani, S., Thoracolumbar vertebral number: the first skeletal synapomorphy for afrotherian mammals. Syst Biodivers 2007. 5: 1–17.
  10. ^ Benstead, J. P., and L. E. Olson. 2003. Limnogale mergulus, web-footed tenrec or aquatic tenrec. Pages 1267–1273 in The natural history of Madagascar (S. M. Goodman and J. P. Benstead, eds.). University of Chicago Press, Chicago.
  11. ^ Olson LE, Goodman SM: Phylogeny and biogeography of tenrecs. In The Natural History of Madagascar Edited by: Goodman SM, Benstead JP. Chicago: Chicago University Press; 2003:1235-1242.
  12. ^ 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
  13. ^ Asher RJ, Hofreiter M: Tenrec phylogeny and the noninvasive extraction of nuclear DNA. Syst Biol 2006, 55:181-194.
  14. ^ Asher, R. J. and Lehmann, T. 2008. Dental eruption in afrotherian mammals. BMC Biol 6: 14.

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