Tupaia (genus)

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Tupaia
Tupaia minor.jpg
Pygmy treeshrew
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Scandentia
Family: Tupaiidae
Genus: Tupaia
Raffles, 1821
Synonyms

Chladobates Schinz, 1824
Cladobates F. Cuvier, 1825
Gladobates Schinz, 1824
Glipora Jentink, 1888
Glirisorex Scudder, 1882
Glisorex Desmarest, 1822
Glisosorex Giebel, 1855
Hylogale Temminck, 1827
Hylogalea Schlegel and Mueller, 1843
Lyonogale Conisbee, 1953
Palaeotupaia Chopra and Vasishat, 1979
Sorex-glis É. Geoffroy and F. Cuvier, 1822
Tana Lyon, 1913
Tapaia Gray, 1860
Tupaja Haeckel, 1866
Tupaya É. Geoffroy and F. Cuvier, 1822

Tupaia is a treeshrew genus in the Tupaiidae family that was first described by Thomas Stamford Raffles in 1821.[1][2] The name of this genus derives from the Malay word tupai meaning squirrels or small animals that resemble squirrels.[3]

Characteristics[edit]

Raffles described the genus as having an elongated snout, 8 to 10 incisors, well developed limbs, five-toed naked feet, and the sole furnished with projecting pads and sharp claws, with a habit and tail of a squirrel.[2]

Marcus Ward Lyon published a revision of the genus in 1913, and also noted the squirrel-like appearance of Tupaia species, which only lack the long black whiskers and have smaller ears. They don’t have any markings on the face, the naked area of the nose is finely reticulated, an oblique stripe on the shoulder is more or less distinct, and the tail is haired but not tufted. The braincase is about as wide as the maxillary tooth row is long. The temporal fossa is smaller than the orbit. The dental formula is 2.1.3.33.1.3.3. The first pair of upper incisors is longer than the second, while the second pair of lower incisors is slightly larger than the first and third pairs. The lower canines are better developed than the upper ones and stand high above the adjacent premolars. The size of head, body and tail varies between species.[4]

One outstanding characteristic of Tupaia species is their color vision. They have rod and cone visual receptors similar to primates and humans.[5]

Classification and taxonomic history[edit]

When Diard and Duvaucel described the first specimen of the common treeshrew Tupaia glis in 1820, they considered it a species of Sorex.[6]

Subsequent to Raffles description of the genus, the following additional Tupaia species were described:[1]

In the past, various authors proposed to place treeshrews in the ordinal rank Insectivora, or considered them close relatives of primates. Since 1972, the treeshrew families Tupaiidae and Ptilocercidae are grouped in the order Scandentia.[20][21][22]

Distribution and habitat[edit]

Tupaia species range from northeastern India, Burma, and Nicobar Islands eastward to members of the Philippine Islands, and from central China south to Java, Borneo and Sumatra, including islands on the southwest coast. They do not occur on Celebes, nor on islands to the east of Java, with the possible exception of Bali.[4] They inhabit the dense undergrowth of tropical forests. With the exception of Tupaia minor, they are primarily terrestrial and forage on the forest floor, usually below 1.5 m (4.9 ft). Since they are rarely seen crossing wide roads, it is likely that populations are negatively affected by fragmentation of forests caused by logging operations.[23]

Ecology and behaviour[edit]

Early naturalists described wild-caught captive Tupaia specimens as restless, nervous and rapidly reacting to sounds and movements.[4] Their auditory sensitivity is highly developed as the broad frequency range of their hearing reaches far into the ultrasonic.[24]

The shape of the cheek-teeth of Tupaia species indicate that they are foremost insectivores. Captive specimens were reported to hunt ants, flies, crickets, grasshoppers, cockroaches and small beetles. They hold their food between the forelegs while sitting on their haunches. After feeding they smooth the head and face with both forepaws, and lick the lips and palms. They are also fond of water, both to drink and to bathe in.[4] They fortify their diet with soft fruits that are mostly dispersed by birds. They swallow the pulp but reject fibrous components, which they cannot digest due to their long and small intestine and rudimentary cecum.[25]

The well developed olfactory perception of treeshrews enables them to easily detect food among the leaf litter on the forest floor. Their sensitivity for odours coupled with scent-marking of their territories is important in their interaction with conspecifics.[26][27]

Observations of Tupaia species in their natural habitat suggest that they usually form monogamous pairs. Social behaviour differs between species and the available food resources in their territories. Where food is adequate and sufficient, they tolerate conspecifics without engaging in territorial disputes.[23] Common treeshrews observed in the Bukit Timah Nature Reserve defended diminishing food resources by chasing away residents of adjacent areas.[27]

Birds of prey, snakes, and small carnivores are known to hunt treeshrews. Humans have no interest in killing them for food because of their unpleasant taste, and they are rarely seen as pests.[28]

Reproduction and Development[edit]

Treeshrews share more similarity with rodents and squirrels than with primates in regards to their reproduction and development. In contrast to primates, who produce one baby with longer gestation periods, treeshrews generally have litters of 2-3 young and are only in utero for about 45 days. Female treeshrews give birth in nests made of many dry leaves, and are known to leave the young unattended while returning occasionally to give them milk. Parental care of Tupaia is relatively limited.[29] The young remain in the nest for 33 days on average, developing gradually before they exit the nest. There are ten identified embryonic developmental stages in Tupaia.[30] Baby tree shrews are sexually immature until about 90 days after birth.[21]

Medical Research[edit]

Their morphological similarity to primates makes them an important model organism in human medical research. A study investigating the effects of the Borna disease virus on tree shrews has given new insight into neurological disease.[31] Since Tupaia share so many similarities with primates yet are more abundant and have more plentiful progeny than them, there is increasing interest in using them as an alternative model for use as a model in human medical research. Successful psychosocial studies were carried out, and it was found that dramatic behavioral, neuroendocrinal, and physiological changes occurred in subordinate male Tupaia, similar to depressed human patients. Their susceptibility to viruses has also piqued interest in using them to study immune responses to infections such as hepatitis B.[32] Tupaia have been used to overcome the limitations of using rodent models in the study of human biology and disease mechanisms, as well as the development of new drugs and diagnostic tools. Recent studies have utilized tree shrews to study infectious, metabolic, neurological, and psychiatric diseases as well as cancers.[33]

In 2013, the Virology Journal published an article that documents the use of the Tupaia belangeri as medical models for the H1N1 influenza virus. This was advantageous because other possible candidates such as guinea pigs, rats, mice, and other rodents leave gaps in the information especially regarding clinical symptoms and transmission. Tupaia, on the other hand, display moderate systemic and respiratory symptoms as well as pathological changes in the respiratory tract, supporting its use as a beneficial model in H1N1 research.[34]

As knowledge increases regarding the use of treeshrews as medical research models, so do the ethical implications regarding the care of these animals for research purposes.

References[edit]

  1. ^ a b Helgen, K. M. (2005). "Tupaia". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 104. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  2. ^ a b c Raffles, T. S. (1821). "Descriptive Catalogue of a Zoological Collection made on account of the Honourable East India Company, in the Island of Sumatra and its Vicinity, under the Direction of Sir Thomas Stamford Raffles, Lieutenant-Governor of Fort Marlborough; with additional Notices illustrative of the Natural History of those Countries.". The Transactions of the Linnean Society of London (Linnean Society of London) XIII: 239–340. 
  3. ^ Wilkinson, R. J. (1901). A Malay-English dictionary Kelly & Walsh Limited, Hongkong, Shanghai and Yokohama.
  4. ^ a b c d e Lyon, M. W., Jr. (1913). Tree shrews: An account of the mammalian family Tupaiidae. Proceedings of the United States National Museum, 45:1–188.
  5. ^ Shriver, J .G., Noback, C. R. (1967). Color Vision in the Tree Shrew (Tupaia glis). Folia Primatologia 6: 161−169.
  6. ^ Diard, P.M., Duvaucel, A. (1820). "Sur une nouvelle espèce de Sorex — Sorex Glis". Asiatick researches, or, Transactions of the society instituted in Bengal, for inquiring into the history and antiquities, the arts, sciences, and literature of Asia, Volume 14: 470–475.
  7. ^ Horsfield, T. (1824). Zoological researches in Java, and the neighbouring islands. London: Kingsbury, Parbury, & Allen. 
  8. ^ Wagner, J. A. (1841). Das peguanische Spitzhörnchen. In: Die Säugethiere in Abbildungen nach der Natur mit Beschreibungen. Supplementband 2. Erlangen: Expedition des Schreber'schen Säugethier- und des Esper'schen Schmetterlingswerkes. Pp. 42–43.
  9. ^ Schlegel, H. (1857). Tana dorsalis. In: Handleiding Tot de Beoefening der Dierkunde, Ie Deel. Boekdrukkerij van Nys, Breda. Page 59.
  10. ^ Gray, J. E. (1865). Notice of a Species of Tupaia from Borneo, in the Collection of the British Museum. Proceedings of the general meetings for scientific business of the Zoological Society of London: 322.
  11. ^ Zelebor, J. (1868). Cladobates Nicobaricus. In: Reise der österreichischen Fregatte Novara um die Erde. Zoologischer Theil, Band 1 Säugethiere. Wien: Kaiserliche Akademie der Wissenschaften. Pp. 17–19.
  12. ^ Günther, A. G. (1876). Remarks on some Indian and, more especially, Bornean Mammals. Proceedings of the general meetings for scientific business of the Zoological Society of London: 424–428.
  13. ^ a b Thomas, O. (1892). On some new Mammalia from the East-Indian Archipelago. The Annals and Magazine of Natural History 6 (9): 250–254.
  14. ^ Thomas, O. (1893). On some new Bornean Mammalia. The Annals and Magazine of Natural History, 6 (11): 341–347.
  15. ^ Thomas, O. (1893). Description of a new Bornean Tupaia. The Annals and Magazine of Natural History 6 (12): 53–54.
  16. ^ Thomas, O. (1894). On the Palawan Representative of Tupaia ferruginea. The Annals and Magazine of Natural History 6 (13): 367.
  17. ^ Matschie, P. (1898). Säugethiere von den Philippinen. Sitzungsbericht der Gesellschaft Naturforschender Freunde zu Berlin: 38–43.
  18. ^ Miller, G. S. Jr. (1903). Seventy New Malayan Mammals. Smithsonian Miscellaneous Collections 45: 1–73.
  19. ^ Mein, P. and Ginsburg, L. (1997). Les mammifères du gisement miocène inférieur de Li Mae Long, Thaïlande : systématique, biostratigraphie et paléoenvironnement. Geodiversitas 19(4): 783–844.
  20. ^ Butler, P. M. (1972). The problem of insectivore classification. In: K. A. Joysey and T. S. Kemp (eds.) Studies in vertebrate evolution. Oliver and Boyd, Edinburgh. Pp. 253−265.
  21. ^ a b Martin, R. D. (1968). Reproduction and Ontogeny in tree-shrews (Tupaia belangeri), with reference to their general behaviour and taxonomic relationships. Zeitschrift für Tierpsychologie 25(4): 409–495.
  22. ^ McKenna, M. C., Bell, S. K. (1997). Classification of mammals above the species level. Columbia University Press, New York.
  23. ^ a b Emmons, L. (2000). Tupai: A field study of Bornean treeshrews. Berkeley and Los Angeles: University of California Press.
  24. ^ Peterson, E. A., Wruble, S. D., Ponzoli, V. I. (1968). Auditory responses in tree shrews and primates. Journal of Auditory Research 8(3): 345–355.
  25. ^ Emmons, L. H. (1991). Frugivory in Treeshrews (Tupaia). The American Naturalist. 138(3): 642–649.
  26. ^ Gould, E. (1978). The behavior of the moonrat, Echinosorex gymnurus (Erinaceidae) and the pentail shrew, Ptilocercus lowi (Tupaiidae) with comments on the behavior of other insectivora. Zeitschrift für Tierpsychologie 48(1): 1–27.
  27. ^ a b Kawamichi, T. and Kawamichi, M. (1979). Spatial Organization and Territory of Tree Shrews (Tupaia glis). Animal Behavior 27(2): 381–393.
  28. ^ Cisneros, L. (2005). "Tupaia glis" (On-line), Animal Diversity Web.
  29. ^ Collins, P. M. and Tsang, W. N. (1987). Growth and reproductive development in the male treeshrew (Tupaia belangeri) from birth to sexual maturity. Biology of reproduction 37(2): 261–267.
  30. ^ Kuhn, H, and Schwaier, A. (1973). Implantation, early placentation, and the chronology of embryogenesis in Tupaia belangeri. Zeitschrift für Anatomie und Entwicklungsgeschichte 142(3): 315–340.
  31. ^ Sprankel, H., Richarz, K., Ludwig, H. and Rott, R. (1978). Behavior Alterations in Tree Shrews Induced by Borna Disease Virus. Medical Microbiology and Immunology 165(1): 1–18.
  32. ^ Cao, J., Yang, E. B., Su, J. J., Li, Y., Chow, P. (2003). The Tree Shrew: Adjuncts and Alternatives to Primates as Models for Biomedical Research. Journal of Medical Primatology. 32(3): 123–130.
  33. ^ Xu, L., Zhang, Y., Liang, B., Lü, L. B., Chen, C. S., Chen, Y. B., Yao, Y. G. (2013). Tree shrews under the spot light: emerging model of human diseases. Dongwuxue Yanjiu 34(2): 59–69. (in Chinese)
  34. ^ Yang, Z. F., Zhao, J., Zhu, Y. T., Wang, Y. T., Liu, R., Zhao, S. S., Li, R. F., Yang, C., Li, J., Zhong, N. S. (2013). The tree shrew provides a useful alternative model for the study of influenza H1N1 virus. Virology Journal 10 (1): 111.