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NAS - Nonindigenous Aquatic Species |
Common Name: African Clawed Frog
Synonyms and Other Names: common platanna
Identification: Xenopus laevis is a flattened frog with a small head and a SVL (snout-vent length) of 50-over 130 mm (2-over 5 in) (Passmore and Carruthers, 1995; Kobel et al., 1996; Channing, 2001; Stebbins, 2003). The small, lidless eyes are located dorsally and turned upward (Stebbins, 2003). There is no visible tympanum (Channing, 2001). The forefeet have slender, unwebbed fingers (Channing, 2001; Stebbins, 2003), which are generally held pointed in a forward direction. In mature adults, the hindfeet are large, fully webbed, and have sharp black claws on the three innermost toes (Channing, 2001; Stebbins, 2003). These frogs have no tongue (Stebbins, 2003), and a minute tentacle is located beneath each eye (Passmore and Carruthers, 1995; Channing, 2001; Stebbins, 2003). The skin is very smooth except where the lateral line sensory system gives it a "stitched" appearance (Stebbins, 2002). The dorsal coloration of X. laevis is olive to brown, often with blotches, spots, or mottling (Passmore and Carruthers, 1995; Kobel et al., 1996; Channing, 2001; Stebbins, 2003). The African clawed frog does not hold its legs beneath itself to raise its body above the substrate when on land. No other frog in North America looks like this representative from the family Pipidae. The underwater calls, which are vocalized by both sexes, consist of long, rapid, high trills that slow down to a rattling "riitrriirrr…" (Kobel et al., 1996; Stebbins, 2003). The unique tadpole is translucent, has a tentacle on each side of its mouth, and a slender tail ending in a filament (St. Amant and Hoover, 1973; Thompson and Franks, 1978, 1979; Channing, 2001; Stebbins, 2003).
Xenopus laevis has been illustrated by a variety of authors (St. Amant and Hoover, 1973; von Filek, 1973; Deucher, 1975; Thompson and Franks, 1978, 1979; Stebbins, 1985, 2003; Videler and Jorna, 1985; Wever, 1985; Alderton, 1986; Mattison, 1987; Bartlett, 1989; Nieuwkoop and Faber, 1994; Passmore and Carruthers, 1995; Davies and Davies, 1997; Bernardini, 1999; Sire et al., 2000; Channing, 2001; Arnold and Ovenden, 2003).
Size: snout-vent length from 50 to over 130 mm
Native Range:
The indigenous range of X. laevis is in sub-Saharan Africa including the countries of Namibia, South Africa, Lesotho, Swaziland, Botswana, Mozambique, Zimbabwe, the Congo, southwestern Kenya, eastern Nigeria, Zambia, Angola, Malawi, Tanzania, Sudan, Burundi, Rwanda, Uganda, Cameroon, and Gabon (Kobel et al., 1996; Tinsley et al., 1996; Poynton, 1999; Channing, 2001).
Arizona: Xenopus laevis were intentionally introduced into man-made ponds in Arthur Park Golf Course, Tucson, Pima County, Arizona, in the 1960s (Tinsley and McCoid, 1996). Other X. laevis were released into man-made bodies of water in southern Arizona by the same individual (Tinsley and McCoid, 1996). D. Swann (personal communication 1997) also has recently observed X. laevis in golf course ponds in Tucson.
California: In California, X. laevis were first collected from several localities in Orange County (Westminster, East Garden Grove-Winterburg Channel, Slater Lake, Fountain Valley [Ocean View Channel and an associated lake], and Greenfield-Banning Channel southeast of the Santa Ana River) in the late 1960s through the early 1970s (Lenaker, 1972; St. Amant and Hoover, 1973; Bury and Luckenbach, 1976; Tinsley and McCoid, 1996). Additional specimens were collected in Irvine, Orange County, in 1989 (Tinsley and McCoid, 1996). Since it was first introduced to California, X. laevis has been found in the following counties: San Bernardino County (Prado Basin, Chino Hills State Park) (Stebbins, 2003), San Diego County (Sweetwater [west Mt. Helix area], San Diego, Otay, and Tijuana Rivers, Tecolote Creek, and Spring Valley) (Bury and Luckenbach, 1976; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; output from California Academy of Sciences), Santa Barbara County (Goleta Slough) (Stebbins, 2003), Los Angeles County (Santa Clara River, Munz Lake, Palmdale, Upper Rio Hondo, Compton Creek, Vasquez Rocks County Park, Edwards Air Force Base [Piute Ponds], and ponds and streams in Soledad, Agua Dulce and Placerita Canyons) (Bury and Luckenbach, 1976; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; output from California Academy of Sciences), Riverside County (Arroyo Seco Creek and surrounding ponds, Santa Margarita River drainage, Vail Lake, and Riverside city) (McCoid and Fritts, 1980, 1989; Stebbins, 1985, 2003; Tinsley and McCoid, 1996), Imperial County (irrigation canals) (Stebbins, 1985), Ventura County (Santa Clara River and estuary, and Vern Freeman Diversion at Saticoy), Kern County (Edwards Air Force Base) (Stebbins, 2003), (Lafferty and Page, 1997; output from California Academy of Sciences), and Yolo County (University of California Davis campus) (Tinsley and McCoid, 1996; Stebbins, 2003).
Since it was first introduced to California, X. laevis has been found in the following counties: San Bernardino County (Prado Basin, Chino Hills State Park) (Stebbins, 2003), San Diego County (Sweetwater [west Mt. Helix area], San Diego, Otay, Rancho Jamul, and Tijuana Rivers, Tecolote and Dulzura Creeks, and Spring Valley) (Bury and Luckenbach, 1976; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; Kuperman et al., 2004; output from California Academy of Sciences), Santa Barbara County (Goleta Slough) (Stebbins, 2003), Los Angeles County (Santa Clara River, Munz Lake, Palmdale, Upper Rio Hondo, Compton Creek, Vasquez Rocks County Park, Edwards Air Force Base [Piute Ponds], and ponds and streams in Soledad, Agua Dulce and Placerita Canyons) (Bury and Luckenbach, 1976; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; output from California Academy of Sciences), Riverside County (Arroyo Seco Creek and surrounding ponds, Santa Margarita River drainage, Santa Ana River, Vail Lake, and Riverside city) (McCoid and Fritts, 1980, 1989; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; Kuperman et al., 2004), Imperial County (irrigation canals) (Stebbins, 1985), Kern County (Edwards Air Force Base) (Stebbins, 2003), San Francisco County (Lily Pond in Golden Gate Park, San Francisco) (E. Mills in Lagos, 2004), Ventura County (Santa Clara River and estuary, and Vern Freeman Diversion at Saticoy) (Lafferty and Page, 1997; output from California Academy of Sciences), and Yolo County (University of California Davis campus) (Tinsley and McCoid, 1996; Stebbins, 2003).
Colorado: In June 1990, a single X. laevis
was found under a submerged log in a relic beaver pond associated with
the North Fork of the Snake River, Summit County, Colorado (Bacchus et
al., 1993; Tinsley and McCoid, 1996; Livo et al., 1998). The water was
partially frozen and slushy (Bacchus et al., 1993).
Florida: In 1964, 200 African clawed frogs were
released into Hialeah (Red Road) Canal, Hialeah, Dade County, Florida,
by an animal importer (King and Krakauer, 1966). An additional Florida
record includes a single X. laevis found near Tampa, Hillsborough County, with no date of collection recorded (Tinsley and McCoid, 1996).
Massachusetts: Newly transformed X. laevis were collected from a small pond at the Acton Arboretum, Acton, Middlesex County, Massachusetts, in 1993 (Cardoza et al., 1993).
North Carolina: A population of X. laevis
existed in fish hatchery ponds at an unknown locality in North Carolina
during an unspecified period of time (Tinsley and McCoid, 1996). This
is probably the same population cited by McCoid (in McCoid and Kleberg,
1995).
Virginia: A nonindigenous population of X. laevis was first observed in an artificial pond in a nature preserve (unnamed) in Virginia, "south of Washington, D.C.," in 1982 and sampled by R. Tinsley in 1987 (Tinsley and McCoid, 1996). Afterwards, local conservation personnel systematically collected hundreds of adults and juveniles (Tinsley and McCoid, 1996). Ernst et al. (1997) mention 30 recently transformed X. laevis collected from a pond at the Gulf Branch Nature Center, Arlington, Fairfax County, between 15 May and 30 June 1984 (C. Ernst, personal communication 1997). These probably represent the same population mentioned by Tinsley and McCoid (1996).
Wisconsin: In 1972, a "large number" of late-stage larval X. laevis were collected from an artificial pond in Greenfield Park, Milwaukee, Milwaukee County, Wisconsin (Tinsley and McCoid, 1996).
Other U. S. western states: African clawed frogs are "rumored" to occur in Nevada, New Mexico, Utah, and Wyoming (Smith and Kohler, 1978). Perhaps these are the other unnamed states vaguely alluded to by Tinsley and McCoid (1996).
Mexico: Nonindigenous X. laevis seem to have spread into Baja California, Mexico, through the Tijuana River and intersecting irrigation canals from California (Tinsley and McCoid, 1996).
Atlantic: Nonindigenous X. laevis were collected from Ascension Island in the southern Atlantic, in 1944 and 1958, near the summit of Green Mountain (Loveridge, 1959). Additional X. laevis were observed in a mountaintop pond (probably from the same aforementioned population) in the early 1980s (Tinsley and McCoid, 1996).
Europe: Xenopus laevis specimens have been collected in the Hamburg area, Germany, and Gorichem and Utrecht, the Netherlands (Tinsley and McCoid, 1996). In the United Kingdom, populations of X. laevis have been found on the Isle of Wight, southern Wales, London, Kent, and various southwestern waterways in England (Arnold, 1995; Tinsley and McCoid, 1996; Arnold and Ovenden, 2002).
Means of Introduction: In most cases of nonindigenous occurrences the exact means of introduction is not clearly known. However, X. laevis has long been used in laboratory research, for studies in genetics, physiology, biochemistry, developmental biology, human pregnancy diagnosis (Deuchar, 1975; Thompson and Franks, 1978, 1979; Stebbins, 1985, 2003; Tinsley and McCoid, 1996), and they became established in many laboratory aquaria throughout the world in the 1950s and 1960s (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 (Tinsley and McCoid, 1996). Loveridge (1959) claims that the established nonindigenous population of X. laevis on Ascension Island, in the southern Atlantic, was caused by the use of this species in diagnostic testing on that island during the World War II years. Moreover, X. laevis are popular aquarium pets, known for being nondemanding, unusual pets (von Filek, 1973; Alderton, 1986; Bartlett, 1989; Tinsley and McCoid, 1996; Davies and Davies, 1997). Because these frogs live relatively long lives (see below) they are often simply dumped into nearby waters due to loss of interest, the end of an experiment, or misguided ethics (Tinsley and McCoid, 1996). The release of 200 African clawed frogs into a canal in Dade County, Florida, was simply due to an animal importer carelessly dumping unwanted stock (King and Krakauer, 1966). The release of X. laevis into the Tucson area and nearby areas of southern Arizona was intentionally caused by a single individual (Tinsley and McCoid, 1996) – simple curiosity?
Status:
Massachusetts: The status of X. laevis remains unclear in Massachusetts, as the collection of newly transformed frogs (Cardoza et al., 1993) suggests a breeding population that may spread.
Virginia: Large numbers of X. laevis were removed from the artificial pond in Virginia through 1987 up to 1988; this may have eliminated them from this immediate vicinity, but it is not known if any frogs migrated to nearby habitat before this time (Tinsley and McCoid, 1996).
North Carolina: Xenopus laevis were eliminated from the fish hatchery ponds in North Carolina by draining the ponds (Tinsley and McCoid, 1996).
Florida: Currently there is no clear evidence for any established population of X. laevis in Florida (King and Krakauer, 1966; Tinsley and McCoid, 1996).
Wisconsin: No further X. laevis were collected from the artificial pond in Milwaukee, Wisconsin, in subsequent years after 1972, indicating they are not established (Tinsley and McCoid, 1996).
Colorado: Further collecting at the nonindigenous site in Summit County, Colorado, in June 1991 revealed no more African clawed frogs (Bacchus et al., 1993); thus, they are not established.
Arizona: The only established population of X. laevis in Arizona is in the golf course ponds in Tucson, Pima County (Stebbins, 1985, 2003; Tinsley and McCoid, 1996; D. Swann, personal communication 1997). It is probably this population that caused Howland (1996) to consider them established but not widespread in Arizona. African clawed frogs are unlikely to spread from the Tucson area, due to the surrounding desert habitat.
Other U.S. western states: The rumors of X. laevis existing in Nevada, New Mexico, Utah, and Wyoming have never been verified (Smith and Kohler, 1978).
Mexico: Xenopus laevis is established in Baja California, Mexico (Flores-Villela, 1993; Smith and Smith, 1993; Stebbins, 2003). These populations need to be monitored to determine their invasiveness and impact. Other worldwide localities: African clawed frogs are established in the United Kingdom and Ascension Island (Arnold, 1995; Tinsley and McCoid, 1996; Measey, 1998a, 2001; Measey and Tinsley, 1998; Arnold and Ovenden, 2002), and in Chile they are an established, highly invasive species (Tinsley and McCoid, 1996; Lobos and Garín, 2002; Lobos and Measey, 2002). The status of X. laevis in Germany and the Netherlands remains unknown (Tinsley and McCoid, 1996).
Other worldwide localities: African clawed frogs are established in the
Impact of Introduction:
In many parts of its indigenous and nonindigenous range, X. laevis is regarded a pest (Rundquist, 1978; Channing, 2001). In
In
Remarks:
The taxonomy and nomenclature of X. laevis has been summarized or reviewed by Frost (1985, 2000), Kobel et al. (1996), and Collins and Taggart (2002). Channing (2001) lists a variety of vernacular names for African clawed frogs. Several authors have summarized by the biology and natural history of X. laevis (von Filek, 1973; Deuchar, 1975; Thompson and Franks, 1978, 1979; McCoid and Fritts, 1980, 1989; Wever, 1985; Nieuwkoop and Faber, 1994; Passmore and Carruthers, 1995; Tinsley et al., 1996; Lafferty and Page, 1997; Bernardini et al., 1999; Sire et al., 2000; Channing, 2001; Stebbins, 2003; and various contributions compiled by Tinsley and Kobel, 1996).
Stebbins (1985) and Frost (2000) discuss the possibility that nonindigenous X. laevis may represent a composite of different undescribed species; thus, the actual identity of frogs in the
Xenopus laevis is a primarily aquatic, highly adaptable frog that can inhabit almost any body of water, natural or man-made, and tolerates sewage and relatively saline (up to 40%) waters (Passmore and Carruthers, 1995; Tinsley et al., 1996; Lafferty and Page, 1997; Channing, 2001). They can survive fairly cold, temperate climates and can easily disperse overland in order to exploit new habitats, particularly newly created man-made habitats (Tinsley et al., 1996; Channing, 2001; Lobos and Garín, 2002; Lobos and Jaksic, 2005). In Africa and
The possession or importation of X. laevis is prohibited or regulated in the states of
References
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Bacchus, S. T., K. Richter, and P. Moler. 1993. Geographic distribution: Xenopus laevis (African clawed frog).
Bartlett, R. D. 1989. Digest for the Successful Terrarium. Tetra Sales
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Lafferty, K. D., and C. J. Page. 1997. Predation on the endangered tidewater goby, Eucyclogobius newberryi, by the introduced African clawed frog, Xenopus laevis, with notes on the frog's parasites. Copeia 1997(3):589-592.
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Other Resources:
Xenopus laevis (African clawed frog) (Global Invasive Species Program)
Exotic and Nongame Species Requiring a Permit (New Jersey Division of Fish and Wildlife)
Author: Louis A. Somma
Revision Date: 3/24/2005 Citation for this information:
Louis A. Somma. 2008. Xenopus laevis. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
<http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=67> Revision Date: 3/24/2005
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