WikipediaRead full entry
The tenrec is a mammal of the family Tenrecidae, found on Madagascar and in parts of the African mainland. Tenrecs are widely diverse; as a result of convergent evolution, they resemble hedgehogs, shrews, opossums, mice and even otters. 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.
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 in) in length, and can weigh over 1 kilogram (2.2 lb). Although they may resemble shrews, hedgehogs, or otters, they are not closely related to any of these groups, their closest relatives being 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. Continuing work on the molecular and morphological diversity of afrotherian mammals has provided ever increasing support for their common ancestry.
Unusual 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 low body temperatures, sufficiently so that they do not require a scrotum to cool their sperm as most other mammals do.
All species appear to be at least somewhat omnivorous, with invertebrates forming the largest part of their diets. The three species found on the African mainland (Potamogale velox, Micropotamogale lamottei, M. ruwenzorii) have more specialized diets, 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. 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. 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, 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. 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. At least some species of tenrecs are social, living in multigenerational family groups with over a dozen individuals.
Interaction with humans
In the island nation of Mauritius, 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.
There are four subfamilies, 10 genera, and 34 species of tenrecs:
- Subfamily Geogalinae
- Subfamily Oryzorictinae
- Genus Limnogale
- Web-footed tenrec (Limnogale mergulus)
- Genus Microgale
- Short-tailed shrew tenrec (Microgale brevicaudata)
- Cowan's shrew tenrec (Microgale cowani)
- Dobson's shrew tenrec (Microgale dobsoni)
- Drouhard's shrew tenrec (Microgale drouhardi)
- Dryad shrew tenrec (Microgale dryas)
- Pale shrew tenrec (Microgale fotsifotsy)
- Gracile shrew tenrec (Microgale gracilis)
- Microgale grandidieri
- Naked-nosed shrew tenrec (Microgale gymnorhyncha)
- Jenkins' shrew tenrec Microgale jenkinsae
- Northern shrew tenrec (Microgale jobihely)
- Lesser long-tailed shrew tenrec (Microgale longicaudata)
- Microgale macpheei (extinct)
- Major's long-tailed tenrec (Microgale majori)
- Montane shrew tenrec (Microgale monticola)
- Nasolo's shrew tenrec (Microgale nasoloi)
- Pygmy shrew tenrec (Microgale parvula)
- Greater long-tailed shrew tenrec (Microgale principula)
- Least shrew tenrec (Microgale pusilla)
- Shrew-toothed shrew tenrec (Microgale soricoides)
- Taiva shrew tenrec (Microgale taiva)
- Talazac's shrew tenrec (Microgale talazaci)
- Thomas's shrew tenrec (Microgale thomasi)
- Genus Oryzorictes
- Genus Limnogale
- Subfamily Potamogalinae
- Subfamily Tenrecinae
- Savage, RJG, & Long, MR (1986). Mammal Evolution: an illustrated guide. New York: Facts on File. p. 53. ISBN 0-8160-1194-X.
- Nicholl, Martin (1984). Macdonald, D., ed. The Encyclopedia of Mammals. New York: Facts on File. pp. 744–747. ISBN 0-87196-871-1.
- 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): 9967–72. doi:10.1073/pnas.95.17.9967. PMC 21445. PMID 9707584.
- 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.
- 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): 1477–84. doi:10.1098/rspb.2004.2754.
- Asher RJ, Bennet N, Lehmann T. (2009). "The new framework for understanding placental mammal evolution". BioEssays 31 (8): 853–64. doi:10.1002/bies.200900053. PMID 19582725.
- Tabuce, R., Marivaux, L., Adaci, M., Bensalah, M., Hartenberger (2007). "Early tertiary mammals from North Africa reinforce the molecular Afrotheria clade". Proceedings of the Royal Society B 274 (1614): 1159–66. doi:10.1098/rspb.2006.0229.
- 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.
- 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.
- Benstead, J. P.; L. E. Olson (2003). "Limnogale mergulus, web-footed tenrec or aquatic tenrec". In S. M. Goodman and J. P. Benstead. The natural history of Madagascar (Chicago: University of Chicago Press). pp. 1267–73. ISBN 9780226303079.
- Olson LE, Goodman SM (2003). "Phylogeny and biogeography of tenrecs". In Goodman SM, Benstead JP. The Natural History of Madagascar. Chicago: Chicago University Press. pp. 1235–42. ISBN 9780226303079.
- 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.
- Asher RJ, Hofreiter M (2006). "Tenrec phylogeny and the noninvasive extraction of nuclear DNA". Syst Biol 55 (2): 181–94. doi:10.1080/10635150500433649. PMID 16522569.
- Asher, R. J. and Lehmann, T. (2008). "Dental eruption in afrotherian mammals". BMC Biol 6: 14. doi:10.1186/1741-7007-6-14. PMC 2292681. PMID 18366669.
- Bronner, G. N.; Jenkins, P. D. (2005). "Order Afrosoricida". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. pp. 72–77. ISBN 978-0-8018-8221-0. OCLC 62265494.