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   Xenopus laevis (amphibian)   
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    Taxonomic name: Xenopus laevis (Daudin 1802)
    Synonyms: Bufo laevis (Daudin 1802), Dactylethera boiei (Tschudi 1838), Dactylethera laevis (Blanford 1870), Dactylethra capensis (Cuvier 1829), Dactylethra delalandii (Cuvier 1836), Dactylethra levis (Duméril and Bibron 1841), Engystoma laevis (Fitzinger 1826), Leptopus oxydactylus (Mayer 1835), Pipa laevis (Merrem 1820), Xenopus boiei (Wagler 1827)
    Common names: African clawed frog (English), clawed frog (English), clawed toad (English), common platanna (English), Glatter Krallenfrosch (German), upland clawed frog (English)
    Organism type: amphibian
    Xenopus laevis (the African clawed frog) is the standard experimental amphibian used in laboratories pan-globally. Escapees have formed viable and invasive populations in many climates, where individuals are generalist aquatic carnivores, predating on invertebrates, amphibians and fish.
    Description
    Frogs of the genus Xenopus are the only frogs with clawed toes and the African clawed frog (Xenopius leavis) is the largest species, adults reaching 120mm. Larvae are mid-water suspension feeders, having long barbels and little pigmentation.
    Occurs in:
    lakes, water courses, wetlands
    Habitat description
    The African clawed frog is a water-dependent species occurring in a very wide range of habitats, including heavily modified anthropogenic habitats. It lives in all sorts of waterbodies, including streams, but tends to avoid large rivers, and waterbodies with predatory fish. It reaches its highest densities in eutrophic water. It breeds in water; there are no records of it breeding in flowing water. It has very high reproductive potential. It is a highly opportunistic species, and colonizes newly recreated, apparently isolated, waterbodies with ease. It can migrate in large numbers when breeding ponds start to dry up, and the weather is wet (IUCN, Conservation International, and NatureServe. 2006).

    X. laevis exhibit high salt tolerance (40% seawater), pH (5-9) and temperature variation (2-35+). They are capable of aestivation during dry periods. They have been selected as laboratory animals for their ease of maintenance and resistance to disease. They are often available as pets but also distributed via laboratories.

    General impacts
    African clawed frogs predate on and compete with native species. They are possibly toxic to predators. They are also known to make water bodies turbid.
    Notes
    Chytridiomycosis was detected in museum specimens of this species dating back to 1938, and it is hypothesised that the international trade in this species might have introduced this fungal disease to other regions of the world. The disease does not appear to have any detrimental affect on populations of this species (IUCN, Conservation International, and NatureServe. 2006).
    Geographical range
    Native range: Angola; Botswana; Burundi; Cameroon; Central African Republic; Congo, The Democratic Republic of the; Kenya; Lesotho; Malawi; Mozambique; Namibia; Nigeria; Rwanda; South Africa; Swaziland; Tanzania; Uganda; Zambia; Zimbabwe (IUCN, Conservation International, and NatureServe. 2006).
    Known introduced range: Chile; France; Indonesia; Mexico; United Kingdom; United States of America (IUCN, Conservation International, and NatureServe. 2006).
    Introduction pathways to new locations
    Other: Exported from South Africa for use in laboratories pan-globally.
    Pet/aquarium trade: Often sold as pets.


    Local dispersal methods
    Escape from confinement: From laboratories and aquaria.
    Natural dispersal (local): Can move overland and through rivers and streams.
    Other (local): Unwanted pets are sometimes introduced to local water bodies.
    Water currents: Animals could be dislodged during floods and are known to move during wet weather and floods.
    Management information
    Preventative measures: The African clawed frog is included in the list of declared animals and birds in Western Australia and has been gazetted as a ‘Declared Animal’ under the Agriculture and Related Resources Protection Act 1976. The catergories assigned to it are A1 = no entry, A2 = eradicate in the wild, A3 = no keeping (Massam et al. 2004).
    Risk Assessment models for assessing the risk that exotic vertebrates could establish in Australia have been further explored by the Western Australia Department of Agriculture & Food (DAFWA) to confirm that they reasonably predict public safety, establishment and pest risks across a full range of exotic species and risk levels.
    The Risk assessment for the African Clawed Frog (Xenopus laevis), has been assigned a VPC Threat Category of EXTREME.
    Mammals and birds were assessed for the pest risk they pose if introduced to Australia, by calculating Vertebrate Pests Committee (VPC) Threat Categories. These categories incorporate risk of establishing populations in the wild, risk of causing public harm, and risk of becoming a pest (eg causing agricultural damage, competing with native fauna, etc). The 7-factor Australian Bird and Mammal Model was used for these assessments.

    Physical and Chemical: Lafferty and Page (1997) suggest that the use of traps may be the best option to lower densities of the African clawed frog in the Santa Clara River Estuary, California, as other options like the use of chemicals or introduction of predatory fish may have devastating effects on native species like the endangered tidewater gobies. Recent studies show that it is not impacted by the herbicide atrazine (IUCN, Conservation International, and NatureServe. 2006).

    Nutrition
    Xenopus laevis prey on aquatic invertebrates, amphibians and fish. They are capable of taking terrestrial prey. Cannabalism of larvae is thought to be important.
    Reproduction
    Sexual. External fertilisation of eggs, which are deposited singly in water. Xenopus laevis has a prolonged breeding season in its native South Africa, and is noted to be year round in California.
    Gravid females are recorded as containing from 1,000 to 27,000 eggs, with larger females producing larger clutches. They will produce multiple clutches in a season under favourable conditions.
    Lifecycle stages
    African clawed frogs are noted for being principally aquatic throughout their lives. Sexual maturity within one year is possible. Eggs are laid singly. Tadpoles typically take 3 months to metamorphosis. Captive adults have been known to live to 20 years. Adults are capable of overland migration.
    Compiled by: IUCN SSC Invasive Species Specialist Group
    Updates with support from the Overseas Territories Environmental Programme (OTEP) project XOT603, a joint project with the Cayman Islands Government - Department of Environment
    Last Modified: Wednesday, 26 May 2010


ISSG Landcare Research NBII IUCN University of Auckland