Disclaimer:

The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: African Clawed Frog

Synonyms and Other Names: Common Platanna.

Taxonomy: available through www.itis.gov

Identification: Xenopus laevis is a primarily aquatic frog that can be easily distinguished from native frog species by its flattened and streamlined bodies, eye placement on top of the head, no visible tympanum which is a sound making organ, and fully webbed hind feet with hard, black claws on the first three toes (Channing 2001, Evans et al. 2015). Their front feet have slender, unwebbed fingers which are often held pointed forward (Channing 2001). These frogs have no tongue and have a small tentacle is located beneath each eye (Channing 2001; Evans et al. 2015). Coloration can vary, but typically the back is olive to brown in color and splotchy/mottled while the underbelly is pale in color (Channing 2001; Dodd 2013).  Xenopus laevis has an obvious lateral line system on the sides of its body that resemble a line of stitches (Dodd 2013; Evans et al. 2015). Tadpoles of the genus Xenopus, including both X. laevis and X. tropicalis, are easily distinguished from native tadpoles by the presence of whisker-like barbels (Cannatella and Trueb 1988). Unlike many native species, X. laevis tadpoles transition from bubble sucking, which is when a tadpole does not breach the surface but sucks air from the water surface thereby capturing a bubble, to breaching the surface to breathe air early in their tadpole development (Phillips et al. 2022) Xenopus tadpoles also school differently from native tadpoles in aggregations where individuals do not touch, but all are oriented in the same way with their heads tipped downward (Caldwell 1989).

Xenopus laevis can easily be confused with X. tropicalis, a smaller aquatic frog with an introduced population located in Hillsborough County, Florida (Goodman et al. 2021). Adult X. laevis are larger than X. tropicalis, growing up to 14 cm in length. Xenopus laevis has a call with lower amplitude change than X. tropicalis which has a more trill-type call with higher changes in amplitude (Tobias et al. 2011). The presence of unfused nasal bones, absence of vomer bones in the nasal cavity, and fusion of the first two vertebrae of the spine are all characteristics of X. tropicalis that can be used to morphologically distinguish them from specimens of X. laevis (Cannatella and Trueb 1988).

Size: total body length 5-14 cm (Stebbins and McGinnis 2012)

Native Range: Xenopus laevis has a historic native range that includes much of southern and sub-Saharan Africa including Namibia, South Africa, Swaziland, Lesotho, Botswana, Zambia, Mozambique, Zimbabwe, Malawi, Democratic Republic of the Congo, and probably Angola (Channing 2001; Measey and Channing 2003).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Xenopus laevis is a primarily aquatic frog that can inhabit almost any body of water and tolerates sewage and relatively saline (up to 14%; or 40% seawater) waters (Channing 2001; Dodd 2013; Tinsley and Kobel 1996). It can survive cold climates and can disperse overland to invade new habitats (Dodd 2013; McCoid and Fritts 1993; Tinsley and Kobel 1996).  X. laevis have been documented in both Africa and Chile to migrate over land in swarms containing hundreds or thousands of individuals (Channing 2001; Lobos and Jaksic 2005; Tinsley and Kobel 1996). Some of these mass migrations are stimulated by droughts and frequently occur at night (Channing 2001; Dodd 2013). In Chile, the species is spreading through land migration and irrigation canlas at a rate of 3.1-3.9 km/year (Lobos and Jaksic 2005). Xenopus laevis can survive droughts by burrowing into the substrate (Channing 2001; Dodd 2013).

Xenopus laevis have a unique sliding pelvis that allows them to avoid predators by diving backwards from the water surface (Videler and Jorna 1985). Moreover, the species has toxins in the skin that can deter predators (Channing 2001). They are carnivores and consume mostly aquatic invertebrates, but also feed on small vertebrates, including terrestrial prey and other X. laevis (Channing 2001; Dodd 2013; Measey 1998). Xenopus laevis can survive starvation conditions for at least 12 months and can rapidly regain lost weight when food becomes available (Tinsley and Kobel 1996).  Adults can live up to 12 years, with a record of over 30 years (Channing 2001; Tinsley et al. 2012).

Xenopus laevis are highly fecund and mate underwater; the male fertilizing thousands of eggs as the female lays them (Channing 2001; Stebbins and McGinnis 2012). Mating may be stimulated by a sudden increase in water or nutrient levels, including sewage outflows (Channing 2001; Tinsley and Kobel 1996). In their native range in Africa, X. laevis breeds regularly during the winter rainfall months, June and July (Channing 2001), but in their invaded range of Southern California, they have been known to breed in every month except November and December (McCoid and Fritts 1993). The tadpoles filter feed on planktonic organisms while suspended upside-down in the water and can occur in high enough densities to almost sterilize the water (Channing, 2001; Stebbins and McGinnis 2012).

Means of Introduction: Xenopus laevis are popular aquarium pets (Tinsley and McCoid 1996), their release from the trade has been reported at least in Miami-Dade County, Florida. (King and Krakauer 1966). Xenopus laevis has long been used as a model organism in laboratory research, for studies in genetics, physiology, biochemistry, developmental biology, human pregnancy diagnosis (Shapiro and Zwarenstein 1934; Thompson and Franks 1979; Tinsley and McCoid 1996). Earliest reports of established nonindigenous populations of X. laevis worldwide are coincident with the end of their use in human pregnancy diagnosis (Measey et al. 2012; Tinsley and McCoid 1996).

Status: Xenopus laevis are established and breeding in several counties throughout California, one golf course in Tuscon, Arizona (Dodd 2013), and in the Puget Sound area of the Pacific Northwest (Reed Ojala-Barbour et al. 2021). It was thought that there was an established population of X. laevis in Hillsborough County, Florida since the 1970’s, but further analysis revealed that the population was actually X. tropicalis (Goodman et al. 2021). There have been many populations in other states that failed to establish or have been successfully eradicated (Dodd 2013). Xenopus laevis is established in many other countries including Mexico, Chile, the United Kingdom, France, Italy, Portugal, Japan, and China (Measley et al. 2012, Wang et al. 2019).

Impact of Introduction:

Summary of species impacts derived from literature review. Click on an icon to find out more...

Ecological	Economic

Xenopus laevis are generalist predators that mainly consume aquatic invertebrates, but aquatic vertebrates, terrestrial invertebrates, and terrestrial vertebrates are commonly found in their diet (Channing 2001; Dodd 2013). These indiscriminate predators will cannibalize, both their own tadpoles and other adults, which allows them to persist in invaded areas with a depleted prey population (McCoid and Fritts 1993). In water bodies with an established population of X. laevis, declines in reproduction of native amphibians have been recorded (Lillo et al. 2011). A significant niche overlap was found between X. laevis and native anurans (frogs and toads) suggesting that interspecific competition occurs (Courant et al. 2018).

This species is a vector for Ranaviruses and Batrachochytrium dendrobatidis (chytrid) fungus, which is a disease that affects the skin of amphibians which can cause death has the potential to devastate native amphibians (Robert et al. 2011; Secondi et al. 2016, Weldon et al. 2004). Additionally, African Clawed Frogs harbor at least 25 genera of parasites, many of which are host-specific (Dodd 2013, Tinsley and Kobel 1996), and individuals from nonindigenous populations in California harbor at least 10 species of parasites (Kuperman et al. 2004).

In Southern Africa, migrations of X. laevis have been implicated in obstructing irrigation pipes and invading houses (Tinsley and Kobel 1996) and aquaculture facilities where they consume both fish and fish food (Channing 2001; McCoid and Fritts 1993).

Remarks: There is evidence in support of X. laevis as a possible origin and cause of spread of Batrachochytrium dendrobatidis (chytrid) fungus (Weldon et al. 2004) which has devastated amphibian populations globally. This fungus negatively affects anurans on all continents where frogs occur except Africa, where Xenopus laevis is native (Stebbins and McGinnis 2012). The spread of chytrid around the world aligns with the heavy exportation of Xenopus laevis beginning in the 1930’s for pregnancy testing (Weldon et al. 2004).

References: (click for full references)

Caldwell, J.P. 1989. Structure and behavior of Hyla geographica tadpole schools, with comments on classification of group behavior in tadpoles. Copeia 1989(4):938-948. https://www.jstor.org/stable/1445980?seq=1.

Cannatella, D.C., and L. Trueb. 1988. Evolution of Pipoid Frogs: Morphology and Phylogenetic Relationships of Pseudhymenochirus. Journal of Herpetology 22(4):439-456. https://www.jstor.org/stable/1564339.

Courant, J., Secondi, J., Vollette, J., Herrel, A., Thirion, J-M. 2018. Assessing the impacts of the invasive frog, Xenopus laevis, on amphibians in western France. Amphibia-Reptilia 24 Apr 2018:1-9. https://brill.com/view/journals/amre/39/2/article-p219_7.xml?language=en.

Channing, A. 2001. Amphibians of Central and Southern Africa (just the section on Xenopus laevis). Comstock Publishing Associates, Cornell University Press.

Dodd, C. K Jr. 2013. Frogs of the United States and Canada. Volume 2. The Johns Hopkins University Press, Baltimore, MD.

Evans, B.J., T.F. Carter, E. Greenbaum, V. Gvoždík, D.B. Kelley, P.J. McLaughlin, O.S.G. Pauwels, D.M. Portik, E.L. Stanley, R.C. Tinsley, M.L. Tobias, and D.C. Blackburn. 2015. Genetics, morphology, advertisement calls, and historical records distinguish six new polyploid species of African Clawed Frog (Xenopus, Pipidae) from West and Central Africa. PLoS ONE 10(12):1-51. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0142823.

Goodman, C.M., G.F.M. Jongsma, J.E. Hill, E.L. Stanley, Q.M. Tuckett, D.C. Blackburn, and C.M. Romagosa. 2021. A case of mistaken identity: genetic and anatomical evidence reveals the cryptic invasion of Xenopus tropicalis in Central Florida. Journal of Herpetology 55(1):62-69. https://doi.org/10.1670/20-083.

King, W., and T. Krakauer. 1966. The exotic herpetofauna of Southeast Florida. Quarterly Journal of the Florida Academy of Sciences 29(2):144-154.

Kuperman, B.I., V.E. Matey, R.N. Fisher, E.L. Ervin, M.L. Warburton, L. Bakhireva, and C.A. Lehman. 2004. Parasites of the African clawed frog, Xenopus laevis, in southern California, U.S.A. Comparative Parasitology 71(2):229-232

Lillo, F., F.P. Faraone, and M.L. Valvo. 2011. Can the introduction of Xenopus laevis affect native amphibian populations? Reduction of reproductive occurrence in presence of the invasive species. Biological Invasions 13:1533-1541.

Lobos, G., and F.M. Jaksic. 2005. The Ongoing Invasion of African Clawed Frogs (Xenopus laevis) in Chile: Cause of Concern. Biodiversity and Conservation 14:429-439.

McCoid, M.J., and T.H. Fritts. 1993. Speculations on colonizing success of the African Clawed Frog, Xenopus laevis (Pipidae), in California. South African Journal of Zoology 28(1):59-61.  

Measey, G.J. 1998. Terrestrial prey capture in Xenopus laevis. Copeia 1998(1):787-791. https://www.jstor.org/stable/1447816.

Measey, G.J., and A. Channing. 2003. Phylogeography of the genus Xenopus in southern Africa. Amphibia-Reptilia 24:321-330.

Measey, G.J., D. Rödder, S.L. Green, R. Kobayashi, F. Lillo, G. Lobos, R. Rebelo, and J.-M. Thirion. 2012. Ongoing invasions of the African clawed frog, Xenopus laevis: a global review. Biological Invasions 14:2255-2270.

Phillips, J.R., A.E. Hewes, M.C. Womack, and K.E. Schwenk. 2022. The mechanics of air breathing in African clawed frog tadpoles, Xenopus laevis (Anura: Pipidae). Journal of Experimental Biology 225(10):1-12. https://journals.biologists.com/jeb/article/225/10/jeb243102/275415/The-mechanics-of-air-breathing-in-African-clawed.

Reed Ojala-Barbour, R., R. Visser, T. Quinn, and M. Lambert. 2021. African Clawed Frog (Xenopus laevis) Risk Assessment, Strategic Plan, and Past Management for Washington State Department of Fish and Wildlife. Washington Department of Fish and Wildlife. https://wdfw.wa.gov/sites/default/files/publications/02267/wdfw02267.pdf.

Robert, J., E. George, F.D.J. Andino, and G. Chen. 2011. Waterborne infectivity of the ranavirus Frog-Virus 3 in Xenopus laevis. Virology 417(2):410-417.

Secondi, J., T. Dejean, A. Valentini, B. Audebaud, and C. Miaud. 2016. Detection of a global aquatic invasive amphibian, Xenopus laevis, using environmental DNA. Amphibia-Reptilia 37:131-136. https://brill.com/view/journals/amre/37/1/article-p131_14.xml?ebody=pdf-67975.

Shapiro, H.A., and H. Zwarenstein. 1934. A rapid test for pregnancy on Xenopus laevis. Nature 133:762.

Stebbins, R.C., and S. M. McGinnis. 2012. Field Guide to the Amphibians and Reptiles of California. Revised Edition. University of California Press, Berkeley and Los Angeles.

Thompson, D.E., and R.L. Franks. 1979. Xenopus. Carolina Tips 42(2):4-8. 

Tinsley, R.C., and H.R. Kobel (editors). 1996. The Biology of Xenopus. The Zoological Society of London, Oxford. 

Tinsley, R.C., and M.J. McCoid. 1996. Feral populations of Xenopus outside Africa. Pages 81-94 in Tinsley, R.C., and H.R. Kobel, eds. The biology of Xenopus. Oxford University Press. Oxford, England.

Tinsley, R., L. Stott, J. York, A. Everard, S. Chapple, J. Jackson, M. Viney, M.C. Tinsley. 2012. Acquired immunity protects against helminth infection in a natural host population: long-term field and laboratory evidence. International Journal for Parasitology 42:931-938.  

Tobias, M.L., B.J. Evans, and D.B. Kelley. 2011. Evolution of advertisement calls in African clawed frogs. Behaviour 148(4):519-549. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3978194/.

Videler, J.J., and J.T. Jorna. 1985. Functions of the Sliding Pelvis in Xenopus laevis. Copeia 1985(1):251-254. https://www.jstor.org/stable/1444825.

Wang, S., Y. Hong, and J. Measey. 2019. An established population of African clawed frogs, Xenopus laevis (Daudin, 1802), in mainland China. BioInvasions Records 8(2):457-464. https://scholar.sun.ac.za/server/api/core/bitstreams/ee7f12f0-9d99-4587-bea9-a562a3af471b/content.

Weldon, C., L.H. du Preez, A.D. Hyatt, R. Muller, and R. Speare. 2004. Origin of the amphibian chytrid fungus. Emerging Infectious Diseases 10(12):2100-2105. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3323396/.

Other Resources:
US Fish and Wildlife Service Ecological Risk Screening Summary for Xenopus laevis

Author: Stratton, L.D. and L.A. Somma

Peer Review Date: 3/21/2024

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.