Xenopus gilli was first described by Rose and Hewitt (1927). It is a tetraploid species with a chromosome number of 36 (Tinsley and Kobel 1996). The females average 55 mm in length and can be as long as 60 mm, while the males are about 30% the length of females. X. gilli has a pointed head and contains a lower eyelid that covers almost half its eye. Furthermore, X. gilli has no subocular tentacle and has one less toe than most other Xenopus species. X. gilli has a dorsal color that is yellowish-brown and has two or four bands of dark spots behind the eyes. In addition, X. gilli tends to be heavily spotted ventrally, although several specimens have been found to be spotless. The clear and distinct markings on X. gilli make it easily distinguishable from other closely related Xenopus species such as X. laevis (Tinsley and Kobel 1996).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: South Africa
X. gilli is found in the highly acidic black lakes found in the Cape Floral Kingdom (fynbos biome) of South Africa. Except for a few exceptions, X. gilli is situated in coastal lowlands in the Cape Peninsula and Cape Agulhas. Geographically, it is restricted to acidic black-waters that facilitate the breakdown of phenolic-rich plant matter to organic acids such as hubic, fulvic, hymenomelanic, and humin, which are vital for the species (Tinsley and Kobel, 1996). Biome/Ecosystem: Freshwater, Terrestrial Habitat: Mediterranean-type Shrubby Vegetation Wetland - Permanent Freshwater Marshes/Pools Wetland - Seasonal/intermittent Freshwater Marshes/Pools Artificial/Aquatic - Ponds (below 8 ha). 
Life History, Abundance, Activity, and Special Behaviors
Life History/Abundance – X. gilli is a very rare species that was only known in eight locations in South Africa before 1970. Later in 1985, it was found in locations farther east and was believed to span 35 localities. Although X. gilli’s distribution is restricted by the necessity of an acidic environment, it was believed to once have occupied as 75 different localities in South Africa (Tinsley and Kobel 1996). However, by 2004, X. gilli was believed to occupy less than 5 locations in South Africa (ICUN Red List 2006). Special Behaviors – X. gilli has a call that resembles short trill that occur at a rate of 1-3 per second (Tinsley and Kobel 1996). X. gilli also interbreeds with X. laevis. The two species interbreed when X. laevis gains access to the ponds inhabited by X. gilli due to disturbances in the ponds. X. gilli and X. laevis are physically different in many ways including size, coloration, and morphological features. Based on these differences, the hybrids fall into two categories: X. gilli-like or X. laevis-like (Tinsley and Kobel 1996). X. laevis tend to greatly outnumber of X. gilli, which often leads to mismating. This interbreeding is contributing further to the decline of X. gilli.
Trends and Threats
X. gilli is listed as endangered because its area occupancy is less than 500 km and because there is a continuing decline in its habitats as well as the number of mature individuals (IUCN Red List 2006). X. gilli has been the victim of land development. Various farming practices and the construction of dams destroyed the specie’s natural habitats. The Cape of Good Hope Natural Reserve decided to introduce new fauna into the area, which further altered X. gilli’s surroundings. Once X. gilli and X. laevis began to interbreed, sterile male hybrids led to even greater risk of X. gilli going extinct (Aslett 2004).
Relation to Humans
When concern was raised about the future of the species, scientists began to take action, proposing to drive out the X. laevis species in order to protect the future of X. gilli. However, scientists realized that X. laevis had been too deeply rooted in the habitat but are still making efforts to remove other introduced fauna and alien vegetation from the area. Scientists also pushed for new legislations to conserve the status of the area and in 1998, the area was proclaimed Cape Peninsula National Park. In hopes of preserving the rare and unique species X. gilli, humans are slowly making progress to undo the damage that was inflicted on the habitat of X. gilli (Aslett, 2004).
Possible reasons for amphibian decline
General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Loss of distinctiveness through hybridization
Aslett, C. “Endangered Clawed Frog: Xenopus gilli.” http://clawedfrogs.tripod.com/index.html Download on: 02 November 2006.
Harrison, J., Measey, J., Tinsley, R., and Minter, L. 2004. Xenopus gilli. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 02 November 2006.
Tinsley, R.C. and Kobel, H.R. (1996). The Biology of Xenopus. Oxford Scientific Press, Oxford.
Written by Arman Zaman (armansz AT berkeley.edu), URAP
First submitted 2007-01-26
Edited by Tate Tunstall (2007-02-07)
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