Tarsier

Tarsiers[1]
Temporal range: 45–0 Ma
Late Eocene to Recent
Philippine Tarsier (Tarsius syrichta)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorrhini
Infraorder: Tarsiiformes
Family: Tarsiidae
Gray, 1825
Genus: Tarsius
Storr, 1780
Type species
Tarsius tarsier
Erxleben, 1777
Species

See text
Synonyms
  • Cephalopachus Swainson, 1835
  • Hypsicebus Lesson, 1840
  • Macrotarsus Link, 1795
  • Rabienus Gray, 1821

Tarsiers are haplorrhine primates of the genus Tarsius, a genus in the family Tarsiidae, which is itself the lone extant family within the infraorder Tarsiiformes. Although the group was once more widespread, all the species living today are found in the islands of Southeast Asia.

Contents

Evolutionary history

Fossil record

Fossils of tarsiiform primates are found in Asia, Europe, and North America, and there are disputed fossils from Africa, but extant tarsiers are restricted to several Southeast Asian islands including the Philippines, Sulawesi, Borneo, and Sumatra. The fossil record indicates that their dentition has not changed much, except in size, in the past 45 million years.

Within the family Tarsiidae, there are two extinct genera, Xanthorhysis and Afrotarsius. However, the placement of Afrotarsius is not certain,[2] and is sometimes listed in its own family, Afrotarsiidae, within the infraorder Tarsiiformes,[3] or considered an anthropoid primate.[4]

So far three fossil species of the genus Tarsius are known from the fossil record:

The genus Tarsius has a longer fossil record than any other primate genus, but the assignment of the Eocene and Miocene fossils to the genus is questionable.[7]

Classification

The phylogenetic position of extant tarsiers within the order Primates has been debated for much of the past century, and tarsiers have alternately been classified with strepsirrhine primates in the suborder Prosimii, or as the sister group to the simians (=Anthropoidea) in the infraorder Haplorrhini. Analysis of SINE insertions, a type of macromutation to the DNA, is argued to offer very persuasive evidence for the monophyly of Haplorrhini, where other lines of evidence, such as DNA sequence data, remain ambiguous. Thus, some systematists argue that the debate is conclusively settled in favor of a monophyletic Haplorrhini. In common with simians, tarsiers have a mutation in the L-gulonolactone oxidase (GULO) gene which confers need for vitamin C in the diet. Since the strepsirrhines do not have this mutation and have retained the ability to make vitamin C, the genetic trait which confers the need for it in the diet would tend to place tarsiers with haplorrhines.[8]

At a lower phylogenetic level, it has been indicated that the tarsiers, currently all placed in the genus Tarsius, actually should be placed in two (a Sulawesi and a Philippine-Western group) or three separate genera (a Sulawesi, Philippine and Western group).[1][9] Species level taxonomy is complex, with morphology often being of limited use compared to vocalizations. Several "vocal morphs" may represent undescribed taxa, taxonomically separable from T. tarsier (=spectrum) (such as Minahasa and a tarsier from the Togian Islands), and many others from Sulawesi and surrounding islands (Shekelle & Leksono 2004). This may also be the case for a number of poorly known isolated Philippine populations (such as the Basilan, Leyte and Dinagat populations of the T. syrichta group). Further confusion exists over the validity of certain names. Among others, the widely used T. dianae has been shown to be a junior synonym of T. dentatus, and comparably T. spectrum is now considered a junior synonym of T. tarsier.[1]

In 2010, Colin Groves and Myron Shekelle suggested splitting the genus Tarsius into three genera, the Philippine tarsiers (genus Carlito), the western tarsiers (genus Cephalopachus), and the eastern tarsiers (genus Tarsius). This was based on differences in dentition, eye size, limb and hand length, tail tufts, tail sitting pads, the number of mammae, chromosome count, socioecology, vocalizations, and distribution. Their classification, which includes several newly described species, is as follows:[12]

Anatomy and physiology

Tarsiers are small animals with enormous eyes; each eyeball is approximately 16 mm in diameter and is as large as their entire brain.[13] Tarsiers also have very long hind limbs. In fact, their feet have extremely elongated tarsus bones, from which the animals get their name. The head and body range from 10 to 15 cm in length, but the hind limbs are about twice this long (including the feet), and they also have a slender tail from 20 to 25 cm long. Their fingers are also elongated, with the third finger being about the same length as the upper arm. Most of the digits have nails, but the second and third toes of the hind feet bear claws instead, which are used for grooming. Tarsiers have very soft, velvety fur, which is generally buff, beige, or ochre in color.[14]

Unlike other prosimians, tarsiers lack any toothcomb, and their dental formula is also unique:Upper: 2.1.3.3, lower: 1.1.3.3

Vision

All tarsier species are nocturnal in their habits, but like many nocturnal organisms some individuals may show more or less activity during the daytime. Unlike many nocturnal vertebrates, however, tarsiers lack a light-reflecting area (tapetum lucidum) of the eye and have a fovea.

The tarsier's brain is different from other primates in terms of the arrangement of the connections between the two eyes and the lateral geniculate nucleus, which is the main region of the thalamus that receives visual information. The sequence of cellular layers receiving information from the ipsilateral (same side of the head) and contralateral (opposite side of the head) eyes in the lateral geniculate nucleus distinguishes tarsiers from lemurs, lorises, and monkeys, which are all similar in this respect.[15] Some neuroscientists suggested that "this apparent difference distinguishes tarsiers from all other primates, reinforcing the view that they arose in an early, independent line of primate evolution."[16]

Behavior

Tarsiers are the only extant entirely carnivorous primates: they are primarily insectivorous, and catch insects by jumping at them. They are also known to prey on birds, snakes, lizards, and bats.[14] As they jump from tree to tree, tarsiers can even catch birds in motion.

Gestation takes about six months,[17] and tarsiers give birth to single offspring. Young tarsiers are born furred, and with open eyes, and are able to climb within a day of birth. They reach sexual maturity by the end of their second year. Sociality and mating system varies, with tarsiers from Sulawesi living in small family groups, while Philippine and Western tarsiers are reported to sleep and forage alone.

Tarsiers tend to be extremely shy animals.

Conservation

Tarsiers have never formed successful breeding colonies in captivity. This may be partly due to their special feeding requirements.[18][19][20][21][22]

The sanctuary near the town of Corella, on the Philippine island of Bohol is having some success restoring tarsier populations. The Philippines Tarsier Foundation (PTFI) has developed a large semi-wild enclosure known as the Tarsier Research and Development Center. Lito Pizarras, also known as the "Tarsier man" founded this sanctuary where visitors can watch tarsiers up close in the wild (naturally without touching them). As of 2011, the sanctuary was taken care of by him and his brother. The trees in the sanctuary are populated with nocturnal insects that make up the tarsier's diet.[23]

The 2008 described Siau Island Tarsier is regarded as Critically Endangered and was listed among The World's 25 Most Endangered Primates by Conservation International and the IUCN/SCC Primate Specialist Group in 2008.[24] Malaysian government protects tarsiers by listing them in the Totally Protected Animals of Sarawak, the Malaysian state in Borneo where they are commonly found.[25]

References

  1. ^ a b c d Groves, C. (2005). Wilson, D. E., & Reeder, D. M, eds. ed. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 127–128. OCLC 62265494. ISBN 0-801-88221-4. http://www.bucknell.edu/msw3. 
  2. ^ a b c Gunnell, G.; Rose, K. (2002). "Tarsiiformes: Evolutionary History and Adaptation". In Hartwig, W.C.. The Primate Fossil Record. Cambridge University Press. ISBN 0-521-66315-6. 
  3. ^ McKenna, M.C., and Bell, S.K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 337–340 pp. ISBN 0-231-11013-8
  4. ^ a b Chiamanee, Y., Lebrun, R., Yamee, C., and Jaeger, J.-J. (2010). "A new Middle Miocene tarsier from Thailand and the reconstruction of its orbital morphology using a geometric–morphometric method". Proceedings of the Royal Society B: Biological Sciences: –. doi:10.1098/rspb.2010.2062. 
  5. ^ Rossie, J.B.; Ni, X.; Beard, K.C. (2006). "Cranial remains of an Eocene tarsier" (PDF). PNAS 102 (12): 4381–4385. http://www.pnas.org/content/103/12/4381.full.pdf. 
  6. ^ Nowak, R.M. (1999). Walker's Mammals of the World (6th ed.). Johns Hopkins University Press. pp. 94–97. ISBN 0801857899. 
  7. ^ Simons, E.L. (2003). "The Fossil Record of Tarsier Evolution". In Wright, P.C.; Simons, E.L.; Gursky, S.. Tarsiers: past, present, and future. ISBN 978-0813532363. 
  8. ^ Pollock, J. I. & Mullin, R. J. (1986). "Vitamin C biosynthesis in prosimians: Evidence for the anthropoid affinity of Tarsius". American Journal of Physical Anthropology 73 (1): 65–70. doi:10.1002/ajpa.1330730106. PMID 3113259. http://www3.interscience.wiley.com/journal/110488482/abstract?CRETRY=1&SRETRY=0. 
  9. ^ Brandon-Jones, D.; et al. (2004). "Asian primate classification". International Journal of Primatology 25 (1): 97–164. doi:10.1023/B:IJOP.0000014647.18720.32. 
  10. ^ Shekelle, Myron; Groves, Colin; Merker, Stefan; Supriatna, Jatna (2008). "Tarsius tumpara: A New Tarsier Species from Siau Island, North Sulawesi". Primate Conservation (23): 55–64. http://www.tarsier.org/media_pdf_files/2008-Shekelleetal-PC23-Tarsius%20tumpara.pdf. Retrieved January 2010. 
  11. ^ http://www.springerlink.com/content/l6g2818052rn7r20/fulltext.html
  12. ^ Groves, C.; Shekelle, M. (2010). "The Genera and Species of Tarsiidae" (PDF). International Journal of Primatology 31 (6): 1071–1082. doi:10.1007/s10764-010-9443-1. http://www.springerlink.com/content/j3712t1357863121/fulltext.pdf. 
  13. ^ Shumaker, Robert W.; Benjamin B. Beck (2003). Primates in Question. Smithsonian Books. ISBN 1-58834-151-8. 
  14. ^ a b Niemitz, Carsten (1984). Macdonald, D.. ed. The Encyclopedia of Mammals. New York: Facts on File. pp. 338–339. ISBN 0-87196-871-1. 
  15. ^ Rosa, M. G.; Pettigrew J. D.; Cooper H. M. (1996). "Unusual pattern of retinogeniculate projections in the controversial primate Tarsius". Brain Behavior and Evolution 48 (3): 121–129. doi:10.1159/000113191. 
  16. ^ Collins, C. E.; Hendrickson, A.; Kaas, J. H. (2005). "Overview of the visual system of tarsius". The Anatomical Record Part A 287 (1): 1013–1025. doi:10.1002/ar.a.20263. PMID 16200648. 
  17. ^ Izard, Kay M.; Wright, Simons (1985). "Gestation length in Tarsius bancanus". Am J Primatology 4 (4): 327–331. doi:10.1002/ajp.1350090408. 
  18. ^ Roberts, M.; Kohn, F. (1993). "Habitat Use, Foraging Behavior, and Activity Patterns in Reproducing Western Tarsiers, Tarsius bancanus, in Captivity: A Management Synthesis" (PDF). Zoo Biology 12 (2): 217–232. doi:10.1002/zoo.1430120207. http://si-pddr.si.edu/dspace/bitstream/10088/503/1/Roberts1993.pdf. 
  19. ^ Shekelle, M.; Nietsch, A. (2008). "Tarsier Longevity: Data from a Recapture in the Wild and from Captive Animals". In Shekelle, M.; Maryano, T.; Groves, C. et al. (PDF). Primates of the Oriental Night. LIPI Press. pp. 85–89. ISBN 978-979-799-263-7. http://tarsier.org/products_files/2008-POTON-p85-ShekelleNietsch-Longevity.pdf. 
  20. ^ Severn, K.; Dahang, D.; Shekelle, M. (2008). "Eastern Tarsiers in Captivity, Part I: Enclosure and Enrichment". In Shekelle, M.; Maryano, T.; Groves, C. et al. (PDF). Primates of the Oriental Night. LIPI Press. pp. 91–96. ISBN 978-979-799-263-7. http://www.tarsier.org/products_files/2008-POTON-p91-Severnetal-CaptivityEnclosure.pdf. 
  21. ^ Severn, K.; Dahang, D.; Shekelle, M. (2008). "Eastern Tarsiers in Captivity, Part II: A Preliminary Assessment of Diet". In Shekelle, M.; Maryano, T.; Groves, C. et al. (PDF). Primates of the Oriental Night. LIPI Press. pp. 97–103. ISBN 978-979-799-263-7. http://www.tarsier.org/products_files/2008-POTON-p97-Dahangetal-CaptiveDiet.pdf. 
  22. ^ Fitch-Snyder, H. (2003). "History of Captive Conservation of Tarsiers". In Wright, P.C.; Simons, E.L.; Gursky, S.. Tarsiers: Past, Present, and Future. Rutgers University Press. pp. 227–295. ISBN 0-8135-3236-1. 
  23. ^ Jachowski, David S.; Pizzaras, Carlito (2005). "Introducing an innovative semi-captive environment for the Philippine tarsier (Tarsius syrichta)". Zoo Biology 24 (1): 101–109. doi:10.1002/zoo.20023. 
  24. ^ Shekelle, Myron; Salim, Agus. "Siau Island Tarsier". IUCN/SSC Primate Specialist Group. http://www.primate-sg.org/siau07.htm. Retrieved January 2010. 
  25. ^ "Totally Protected Animals of Sarawak". Forestry Department of Sarawak. http://www.forestry.sarawak.gov.my/forweb/wildlife/mgmt/tpa/tprotsp.htm. Retrieved January 2010. 
General references

External links

Extant primate families by suborder
Kingdom Animalia · Phylum Chordata · Class Mammalia · Infraclass Eutheria · Superorder Euarchontoglires
Strepsirrhini
Haplorhini
Extant species of family Tarsiidae
Kingdom: Animalia · Phylum: Chordata · Class: Mammalia · Order: Primates · Suborder: Haplorrhini
Tarsius
(Tarsiers)
Category