Western clawed frog

The western clawed frog (Xenopus tropicalis) is a species of frog in the family Pipidae, also known as tropical clawed frog.[2] It is the only species in the genus Xenopus to have a diploid genome.[3][4] Its genome has been sequenced,[5][6] making it a significant model organism for genetics that complements the related species Xenopus laevis (the African clawed frog),[7] a widely used vertebrate model for developmental biology. X. tropicalis also has a number of advantages over X. laevis in research, such as a much shorter generation time (<5 months), smaller size (4–6 cm (1.6–2.4 in) body length), and a larger number of eggs per spawn.[8]

Western clawed frog
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Pipidae
Genus: Xenopus
Species:
X. tropicalis
Binomial name
Xenopus tropicalis
(Gray, 1864)
Synonyms
  • Silurana tropicalis
    Gray, 1864

It is found in Benin, Burkina Faso, Cameroon, Ivory Coast, Equatorial Guinea, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Nigeria, Senegal, Sierra Leone, Togo, and possibly Mali. Its natural habitats are subtropical or tropical moist lowland forests, moist savanna, rivers, intermittent rivers, swamps, freshwater lakes, intermittent freshwater lakes, freshwater marshes, intermittent freshwater marshes, rural gardens, heavily degraded former forests, water storage areas, ponds, aquaculture ponds, and canals and ditches.

Description

The western clawed frog is a medium-sized species with a somewhat flattened body and a snout-vent length of 28 to 55 mm (1.1 to 2.2 in), females being larger than males. The eyes are bulging and situated high on the head and there is a short tentacle just below each eye. A row of unpigmented dermal tubercles runs along the flank from just behind the eye, and are thought to represent a lateral line organ. The limbs are short and plump, and the fully webbed feet have horny claws. The skin is finely granular. The dorsal surface varies from pale to dark brown and has small grey and black spots. The ventral surface is dull white or yellowish with some dark mottling.[9]

Distribution and habitat

The western clawed frog is an aquatic species and is found in the West African rainforest belt with a range stretching from Senegal to Cameroon and eastern Zaire. It is generally considered a forest-dwelling species and inhabits slow-moving streams, but it is also found in pools and temporary ponds in the northern Guinea and Sudan savannas.[9]

Biology

In the dry season, this frog lives in shallow streams and hides under tree roots, under flat stones, or in holes in the riverbank. It feeds primarily on earthworms, insect larvae and tadpoles. When the rainy season starts it migrates across the forest floor at night to find temporary pools. Spawning may take place in large pools with much vegetation, but tadpoles are also sometimes found in muddy pools with no vegetation. Single eggs may be attached to plants or they may float. The tadpoles have broad mouths and no jaws, but have long tentacles on their upper lips. The ventral fins of their tails are broader than the dorsal ones. Their body colour is generally orange and the tail transparent but in darker locations the tail may be blackish. The tadpoles feed by filtering zooplankton from the water. In large water bodies, they may form dense swarms. Metamorphosis takes place when the tadpoles measure about 5 cm (2 in) in length.[9]

Status

The IUCN lists the western clawed frog as "Least Concern" because it has a wide distribution and is an adaptable species living in a range of habitats, and the population trend seems to be steady.[1]

Use as a genetic model system
See also Xenopus - Model organism for biomedical research

Xenopus embryos and eggs are a popular model system for a wide range of biomedical research.[3][10] This animal is widely used because of its powerful combination of experimental tractability and close evolutionary relationship with humans, at least compared to many model organisms.[10]

Unlike its sister species X. laevis, X. tropicalis is diploid and has a short generation time, facilitating genetic studies.[3] The complete genome of X. tropicalis has been sequenced. [5] This species has n=10 chromosomes. [11]

Online Model Organism Database

Xenbase[12] is the Model Organism Database (MOD) for both Xenopus laevis and Xenopus tropicalis.[13]

References
  1. Richard Tinsley; Mark-Oliver Rödel; John Measey (2004). "Xenopus tropicalis". IUCN Red List of Threatened Species. 2004. Retrieved 2013-12-06.CS1 maint: ref=harv (link)
  2. Frost, Darrel R. (2014). "Xenopus tropicalis (Gray, 1864)". Amphibian Species of the World: an Online Reference. Version 6.0. American Museum of Natural History. Retrieved 3 March 2015.
  3. Harland, R. M. and Grainger, R. M. 2011. Trends in Genetics vol. 27, p. 507–15
  4. Enrique Amaya, Martin F. Offield, and Robert M. Grainger. "Frog genetics: Xenopus tropicalis jumps into the future". Trends in Genetics. Volume 14, Issue 7, 1 July 1998, pages 253–255.
  5. Hellstein U; Harland RM; Gilchrist MJ; et al. (2010-04-30). "The genome of the Western clawed frog Xenopus tropicalis". Science. 328 (5978): 633–636. Bibcode:2010Sci...328..633H. doi:10.1126/science.1183670. PMC 2994648. PMID 20431018.
  6. JGI X. tropicalis v4.1
  7. Bowes; et al. (2008). "Xenbase: a Xenopus biology and genomics resource". Nucleic Acids Res. 36: D761. doi:10.1093/nar/gkm826.
  8. "Bringing Genetics To Xenopus: Half The Genome, Twice As Fast". University of Virginia. Retrieved 2009-10-24.
  9. M. O. Roedel; Vance Vredenburg; M. J. Mahoney; Tate Tunstall; Kellie Whittaker (2010-05-01). "Xenopus tropicalis". AmphibiaWeb. Retrieved 2013-12-06.
  10. Wallingford, J., Liu, K., and Zheng, Y. 2010.Current Biology vol. 20, p. R263–4
  11. "Xenopus tropicalis (ID 80) - Genome - NCBI". www.ncbi.nlm.nih.gov. Retrieved 2020-12-01.
  12. Karimi K, Fortriede JD, Lotay VS, Burns KA, Wang DZ, Fisher ME, Pells TJ, James-Zorn C, Wang Y, Ponferrada VG, Chu S, Chaturvedi P, Zorn AM, Vize PD (2018). "Xenbase: a genomic, epigenomic and transcriptomic model organism database". Nucleic Acids Research. 46 (D1): D861–D868. doi:10.1093/nar/gkx936. PMC 5753396. PMID 29059324.
  13. "Xenopus model organism database". Xenbase.org.
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