Xenopus laevis varies in size; males (45.6 to 97.5 mm) tend to be be smaller than females (57 to 147 mm). Their heads and bodies are depressed and flattened and they have small round eyes on the top of their heads. The skin is smooth and the hind limbs are long and robust. The three inner toes of the large fully webbed feet have small black claws on them. The body color is usually dark-gray to greenish-brown dorsally, and pale ventrally (Trueb 2003).
It is introduced in several places outside its native range, including the USA where it was first introduced in the 1930s and 1940s for laboratory use and later as an aquarium pet. It was introduced and established locally in California (San Diego, Orange, Riverside, Los Angeles, Ventura, and Imperial counties) and Arizona (Tucson area) (Stebbins 1985, Lafferty ad Page 1997). It has been recorded from, but it is not established in Colorado. It has also been introduced to Chile (introduced in the 1970s to central Chile, Valparaiso to Concepción Provinces), parts of the United Kingdom (extant in south Wales and presumed extirpated from the Isle of Wight [not mapped here], and a number of occasional records from other locations [not mapped], the Departments of Deux-Sèvres and Maine et Loire in France and Java (Indonesia) [not mapped here]. It is introduced also in the Lage stream, about 20 km W of Lisbon, Portugal (Rebelo et al. 2007) and there is a large invasive population in Sicily (Lillo et al. 2005, Faraone et al. 2008) [not mapped here]. It is presumed to occur in southwestern Sudan, but there do not appear to be confirmed records from this country (there is an uncertain record assigned to X. l. sudanensis from Jebel Marrah, Sudan (M. Beier pers. comm. January 2006) [not mapped here]). Records from Congo refer to X. petersii. Its range is also extending in parts of Africa, often by introduction because it is used for live bait, and it has spread extensively in South Africa. This species ranges from sea-level up to 3,000 m asl.
Global Range: Native to Africa. First brought to the U.S. in the 1930s and 1940s for laboratory use and later as an aquarium pet. Introduced and established locally in California (San Diego, Orange, Riverside, Los Angeles, Ventura, and Imperial counties) and Arizona (Tucson area) (Stebbins 1985, Lafferty ad Page 1997). Apparently established in Baja California (see Mahrdt et al. 2003). Recorded but not established in Colorado.
Xenopus laevis occurs naturally in southern Africa. There are substantial introduced populations in California, Chile, Great Britain, and probably many other locations around the world. (Nieukoop and Faber, 1994)
Biogeographic Regions: nearctic (Introduced ); palearctic (Introduced ); ethiopian (Native )
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Distribution and Habitat
This species occurs in savannas of the Republic of South Africa, Kenya, Uganda, Democratic Republic of Congo, and Cameroon. This frog has high tolerance to change in its environment and will survive in nearly any body of water. It can be found in water bodies ranging from ice-covered lakes to desert oases. Unlike most frogs, the African clawed frog can also survive in water with high salinity (Trueb 2003).
X. laevis is widely distributed in sub-Saharan Africa.
Within its southern distribution, it is a common and widespread species, occurring from sea level to nearly 3000 m in Lesotho. In the west, it is apparently absent in areas of extreme aridity, including much of the Kalahari and Bushmanland in Northern Cape Province. Its distribution extends eastward as far as the Great Escarpment, where it comes into contact with X. muelleri in the low-lying parts of Limpopo and Mpumalanga provinces (Text from Minter et al., 2004, © SI/MAB Biodiversity Program).
Xenopus laevis has a unique morphology because it lacks a tongue and a visible ear. The body is flattened and head is wedge-shaped and smaller than the body. It has two small eyes found on the top of the head and no eyelids. Its front limbs are small and are not webbed, and its hind legs are large and webbed and the three inside toes on either foot have claws. It has smooth slippery skin which is multicolored on its back with blotches of olive gray or brown and gray, while the underside is creamy white with a yellow tinge. It has lateral lines along its back. Males weigh about 60 grams, are about 5 to 6 centimeters long, and lack a vocal sac, which most male frogs have. Females weigh about 200 grams, are about 10 to 12 centimeters long, and have cloacal extensions at the end of the abdomen.
(Kaplan, 1995; Chang 1998)
Range mass: 60 to 200 g.
Range length: 5 to 12 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: female larger
Average basal metabolic rate: 0.012 W.
Length: 13 cm
Southern Africa Bushveld
Garman's toad (Amietophrynus garmani) is found in the Southern African bushveld, among other ecoregions. The Southern Africa bushveld is an element of the vast savannas that cover much of southern Africa. There is low endemism in this ecoregion for both flora or fauna, but the charismatic large mammals and rich birdlife characteristic of African savannas are in evidence. The rugged Waterberg Mountains contain the highest levels of species richness and endemism in the region, and are noted for their reptilian endemism. The ecoregion occurs on an extensive, undulating interior plateau, which lies at an elevation between 700 metres (m) to 1100 m. The soils of this plateau are chiefly coarse, sandy and shallow, overlying granite, quartzite, sandstone or shale. The most distinctive topographical feature of the ecoregion is the rugged and rocky Waterberg Mountains, which rise up from the plateau to an elevation of between 1200 m to 1500 m.http://www.eoearth.org/view/article/51cbeeed7896bb431f69b38d/554565bb0cf24df5070a17ee/?topic=51cbfc79f702fc2ba8129ee0
The ecoregion amphibian associates of the Southern African bushveld are: Savanna ridged frog (Ptychadena anchietae); Angola frog (Rana angolensis); African gray treefrog (Chiromantis xerampelina); Senegal running frog (Kassina senegalensis); Striped stream frog (Strongylopus fasciatus); African clawed frog (Xenopus laevis); African split-skin toad (Schismaderma carens); Uzungwe grassland frog (Ptychadena uzungwensis); African ornate frog (Hildebrandtia ornata); Mababe river frog (Phrynobatrachus mababiensis); Marbled sand frog (Tomopterna marmorata); Marbled snout burrower (Hemisus marmoratus); Knocking sand frog (Tomopterna krugerensis), which is found broadly in southern Africa; and the Transvaal short-headed frog (Breviceps adspersus); Mozambique ridged frog (Ptychadena mossambica); Lukula grassland frog (Ptychadena taenioscelis); Horseshoe forest treefrog (Leptopelis bocagii); South African snake-necked frog (Phrynomantis bifasciatus); Boettger's dainty frog (Cacosternum boettgeri); Natal ghost frog (Heleophryne natalensis); Cryptic sandfrog (Tomopterna cryptotis); Mozambique rain frog (Breviceps mossambicus); Long reed frog (Hyperolius nasutus); Muller's clawed frog (Xenopus muelleri); Common reed frog (Hyperolius viridiflavus); Gray's stream frog (Strongylopus grayii); Natal puddle frog (Phrynobatrachus natalensis); Painted reed frog (Hyperolius marmoratus); Garman's toad (Amietophrynus garmani); Gutteral toad (Amietophrynus gutturalis); Transvaal dwarf toad (Poyntonophrynus fenoulheti); and the Flat-back toad (Amietophrynus maculatus).
Example reptilian associates within this ecoregion are: Bibron's worm snake (Typhlops bibronii); Vine snake (Thelotornis capensis); Black mamba (Dendroaspis polylepis); Angola garter snake (Elapsoidea semiannulata); Annobon lidless skink (Panaspis annobonensis); Bark snake (Hemirhagerrhis nototaenia); Bell's hingeback tortoise (Kinixys belliana); Blue throated agama (Acanthocercus atricollis); Blunt-tailed worm lizard (Dalophia pistillum); Bradfield's dwarf gecko (Lygodactylus bradfieldi); the endemic gecko Broadley's rock gecko (Afroedura broadleyi); and the endemic lizards Platysaurus minor and Platysaurus monotropis.
Some of the many mammalian taxa found within the Southern African bushveld are: Burchell's zebra (Equus quagga burchelli); Hippopotamus (Hippopotamus amphibius), a herbivore classified as Vulnerable; Cheetah (Acinonyx jubatus), a carnivore classified as Vulnerable; the Near Threatened White Rhinoceros (Ceratotherium simum); Commerson's roundleaf bat (Tomopterna cryptotis), classified as Near Threatened; Spotted hyena (Crocuta crocuta); and the Mauritian tomb bat (Taphozous mauritianus).
There are numerous avian species found in this ecoregion, a few examples being: the Near Threatened Red footed falcon (Falco vespertinus); Kori bustard (Ardeotis kori); Long-crested eagle (Lophaetus occipitalis); Olive bee eater (Merops superciliosus); Marabou stork (Leptoptilos crumeniferus); Martial eagle (Polemaetus bellicosus); and the Pink-backed pelican (Pelecanus rufescens).
Xenopus laevis lives in warm, stagnant grassland ponds as well as in streams in arid and semi-arid regions. The ponds are usually devoid of any higher plant vegetation, and covered in green algae. Xenopus laevis can tolerate wide variation in water pH, but the presence of metal ions proves toxic. It thrives in temperatures from 60 to 80 degrees Fahrenheit. It is almost totally aquatic, only leaving the water when forced to migrate.
(Nieuwkoop and Faber, 1994; Beck, 1994; Kaplan, 1995, Jack Crayon, personal communication)
Habitat Regions: temperate ; tropical ; freshwater
Aquatic Biomes: lakes and ponds; rivers and streams
Habitat and Ecology
Comments: In the U.S., found in slow streams, irrigation canals, ponds, and lakes. Eggs are attached to aquatic plants or other submerged vegatation, logs, or rocks.
Habitat and Ecology
Prior to the advent of modern agriculture, X. laevis probably occurred in low densities in natural water bodies, such as streams, rivers and their pools. Nowadays, however, the species is also found in a variety of man-made water bodies such as farm dams, ponds, sewage purification works and fish farms. Eutrophic waters seem to produce the highest densities (Text from Minter et al., 2004, © SI/MAB Biodiversity Program).
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Xenopus laevis is a scavenger and eats living, dead, or dying arthropods and other pieces of organic waste. It has a voracious appetite and attacks anything that passes in front of it. It uses extremely sensitive fingers, an acute sense of smell, and its lateral line systems to locate food. Lateral line systems, usually found in fish, detect vibrations in the water. It uses a hyobranchial pump to suck food into its mouth. The claws on its hind feet tear apart larger pieces of food. Tadpoles are exclusively filter feeders
(Avila and Frye, 1977; Beck, 1994)
Animal Foods: insects; aquatic or marine worms; aquatic crustaceans
Primary Diet: carnivore (Insectivore , Scavenger )
Comments: Highly opportunistic, feeds on invertebrates, amphibians and fish. Larvae filter protozoa, bacteria, and other small food particles from the water (Stebbins 1985).
Balantidium endoparasitises rectum of Xenopus laevis
Animal / parasite / endoparasite
attached worm of Camallanus kaapstaadi endoparasitises stomach of Xenopus laevis
Animal / parasite / endoparasite
tapeworm of Cephalochlamys namaquensis endoparasitises ilium of Xenopus laevis
Animal / parasite / endoparasite
cercarium of Diplostomulum xenopi endoparasitises pericardial sac of Xenopus laevis
Animal / parasite / endoparasite
Nyctotherus cordiformis endoparasitises rectum of Xenopus laevis
Animal / parasite / endoparasite
trophozoite of Opalina endoparasitises rectum of Xenopus laevis
Animal / parasite / endoparasite
attached worm of Procamallanus xenopodis endoparasitises stomach of Xenopus laevis
Animal / parasite / endoparasite
larva of Protopolystoma xenopi endoparasitises kidney of Xenopus laevis
Adults are generalist predators and scavengers, and can hold food items in their toothed mouths while breaking it apart with their claws using an overhead kick (Avila and Frye 1978). These behaviours can be detected by other adults in the vicinity and sometimes lead to a feeding frenzy (Frye and Avila 1979). Most food items for post-metamorphic X. laevis are benthic macro-invertebrates, such as chironomid larvae. However, a wide variety of food sources are used from all microhabitats in water bodies, including carrion and terrestrial food items (Measey 1998a, b). Even the largest animals take very small prey items, such as zooplankton and ostracods . X. laevis plays an important role in the ecology of southern African wetlands because it is widespread and abundant, and it is a voracious predator as well as an important prey item for several mammalian, avian and reptilian predators (Text from Minter et al., 2004, © SI/MAB Biodiversity Program).
Xenopus laevis tested positive for Batrachochytrium dendrobatidis in Botswana at the Kanye Youth Centre in April 1969 (Weldon 2005). It also tested positive in the South African cities of Zeekoeivlei in 1938, Moordenaarshoek and Harrismith in 1972, Natal in 1973, Rosendal and Touw River in 1974, Phillipi in 1982, Florisbad in 1987, Koffiefontein and Sannaspos in 1991, Mooi River in 1995, Kommissiepoort in 1996, Windsorton Road in 1998, Stellenbosch and Klapmuts in 2001, Strand, Wellington, and Botrivier in 2002 and Kammieskroon in 2004 (Weldon 2005).
Life History and Behavior
Activity and Special Behaviors
Toward the peak of the dry season, X. laevis will either move from drying water bodies or burrow into the wet mud to aestivate (Text from Minter et al., 2004, © SI/MAB Biodiversity Program).
Comments: Forages at night; rests on the bottom, or hides under rocks during the day.
Development - Life Cycle: metamorphosis
Wassersug (1996) recorded that larvae hatch within two to three days and, after finishing the yolk supply, begin to feed on algae suspended in the water column. Tadpoles display coordinated schooling behaviour, and maintain their position in the water column by means of a characteristic undulating motion of the tail (Text from Minter et al., 2004, © SI/MAB Biodiversity Program).
Tinsley et al. (1996) found that the time to metamorphosis varies with temperature and the abundance of food. In optimal conditions, metamorphosis is possible within two months (Text from Minter et al., 2004, © SI/MAB Biodiversity Program).
African clawed frogs can reach 15 to 16 years old in wild and feral populations. Captive animals have been known to live as long as 20 years.
Status: wild: 16 (high) years.
Status: captivity: 20 (high) years.
Status: captivity: 8.8 years.
Status: captivity: 15.0 years.
Lifespan, longevity, and ageing
Xenopus laevis is sexually mature in 10 to 12 months. Mating can take place during any time of the year, but is most common in the spring, and can take place up to four times per year. Males vocalize during the evening to attract females. Although the male lacks a vocal sac, it produces a mating call by rapid contractions of the intrinsic laryngeal muscles. This mating call sounds like alternating long and short trills. After the female hears this, she responds with either an acceptance call (a rapping sound) or a rejection call (slow ticking sound). This is a nearly unique behavior in the animal world; rarely does a female answer the males call. Mating often takes place at night, when there are few disturbances. The male develops mating pads on the underside of his forearms and hands. The mating embrace, amplexus, is pelvic, whereas most frogs have axillary (front limb) amplexus. The female can release hundreds of sticky eggs during the 3 to 4 hour event, which are typically attached to plants or other anchors, one or more at a time. The eggs grow into tadpoles, which filter feed. The tadpole metamorphoses into a small froglet, with the tail being absorbed into the body and sustaining its nutritional requirements during this period, which lasts about 4 to 5 days. The total change from egg to small frog takes about 6 to 8 weeks.
(Kaplan, 1995; Beck, 1994; Chang, 1998; Kelley, 1998, Jack Crayon, personal communication)
Breeding interval: African clawed frogs can breed up to 4 times each year.
Breeding season: Mating can take place during any time of the year, but is most common in the spring.
Range age at sexual or reproductive maturity (female): 10 to 12 months.
Range age at sexual or reproductive maturity (male): 10 to 12 months.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous
May during all but the coolest periods of the year in southern California (McCoid and Fritts 1989). Female lays several hundred eggs; eggs laid singly or in small clusters (Behler and King 1979).
After heavy rains, X. laevis sometimes leave water bodies en masse, and single individuals are also encountered on the surface in damp weather. These appearances may be associated with movement to and from breeding sites (Du Plessis 1966). Breeding begins at the onset of the rains, thus at different times in the summer and winter rainfall areas (Berk 1938; Kalk 1960). Hey (1949) reported that there are prolonged breeding period throughout the rainy season, and both females and males are able to breed more than once per season (Text from Minter et al., 2004, © SI/MAB Biodiversity Program).
McCoid (1985) found that spawning takes place during the night when couples, in inguinal amplexus, swim around the pond depositing single eggs on any hard substrate (Text from Minter et al., 2004, © SI/MAB Biodiversity Program).
Evolution and Systematics
Peptides on the skin of African clawed frog protect from bacterial infection by having a semiselective binding nature to bacterial pathogen cells affording each peptide the ability to bind a variety of pathogens.
"AMPs [antimicrobial peptides] appear in multiple niches in nature including the skin of higher organisms and the extracellular milieu of bacteria as the primary line of defense against bacteria and fungi. AMPs are much more stable than typical globular proteins—explaining how they can be continually exposed to the natural environment—and are exceptionally efficient at fending off bacterial infection. Indeed, some cationic antimicrobial peptides have shown activity toward pathogenic bacteria under harsh environmental conditions such as thermal (boiling/autoclaving) and chemical denaturants." (Mannoor et al. 2010:19207)
Learn more about this functional adaptation.
Pigments in frog skin change color in response to hormones by moving melanin grains around cells.
"Some frogs, such as the African clawed frog (Xenopus laevis), change colour to cope with sunlight and heat and also to improve their camouflage. They do this by activating cells in their skin that contain granules of melanin, the dark brown pigment. These colour-changing cells, called melanophores, are normally dark but can be triggered by a particular hormone released in the frog. When the hormone binds to the cell wall, it sets off a reaction that moves the pigment granules to the centre of the cell, making it look colourless. Once the hormone detaches, the melanin grains disperse throughout the cell, making it appear dark again." (Sample 2002:21)
Learn more about this functional adaptation.
Molecular Biology and Genetics
Barcode data: Xenopus laevis
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Xenopus laevis
Public Records: 10
Specimens with Barcodes: 39
Species With Barcodes: 1
It is an invasive species all over world because it was used in human pregnancy tests in the 1940's. When more effective means of pregnancy tests were made available, many X. laevis were released all over the world.
IUCN Red List of Threatened Species: least concern
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2008Least Concern(IUCN 2008)
- 2008Least Concern
National NatureServe Conservation Status
Rounded National Status Rank: NNA - Not Applicable
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
IUCN Red List Category and Justification of Conservation Status
X. laevis does not seem to be threatened in any part of its range. X. laevis is a highly invasive species, as is evidenced by the feral populations that have become established in many parts of the world (Text from Minter et al., 2004, © SI/MAB Biodiversity Program).
Life History, Abundance, Activity, and Special Behaviors
These frogs spend most of their life-cycle in the water, only to leave when there is a drought. When a drought occurs, they will burrow into the drying mud. They can survive up to a year without food. Their diet consists of a wide range of animals including fish, crustaceans, insects, and other frogs. They will also scavenge on dead frogs, fish, birds, and small mammals (Trueb 2003).
Comments: May have declined recently in southern California, due possibly to drought and fish predation (McCoid et al. 1993).
Life History, Abundance, Activity, and Special Behaviors
Management Requirements: Rotenone is not an effective control; introduced predatory fishes might be detrimental as a control because of negative impacts on native species; trapping might be a safe method for reducing frog densities (see Lafferty and Page 1997).
Relevance to Humans and Ecosystems
Human activities have transplanted this African frog all over the globe, where some claim it is pushing native species out of their niche (Beck 1994). Others argue that there is no documented case of this occurring (Jack Crayon, pers. comm.)
Xenopus laevis has been used extensively as a laboratory research animal, mostly in the field of vertebrate embryology because females are prolific egg layers and embryos are transparent, making it easy to observe the development of the embryo. During the 1940's, female X. laevis were injected with the urine of a woman. If the human was pregnant, then the injected frog would start to produce eggs. Xenopus laevis was the first vertebrate cloned in the laboratory. Magainins are a family of antibiotics found in the skin of X. laevis, which heals wounded skin rapidly. Magainin is an antibiotic, antifungal, antiparasitic, and antiviral, probably useful to the frog because of the stagnant, microbe filled waters in which it lives in. These magainins have been tested as an antibiotic cream, which works just as well as an oral antibiotic, but without the side effects. Xenopus laevis is also used in lab because it is very easy to care for, breed, and observe.
Positive Impacts: source of medicine or drug ; research and education
Species Impact: This species is a threat to a number of native U.S. amphibians and fishes (e.g., tidewater goby, Lafferty and Page 1997).
Relation to Humans
This is one of the most-studied species of frogs, considered one of the model systems of developmental biology. It is hardy and breeding can be easily induced in the laboratory. Xenopus laevis early development has been studied by developmental biologists for decades and its genome has been fully sequenced. Because it makes a hardy and popular pet, it can also be found in aquariums worldwide. This species has been used as food in African countries (Trueb 2003).
African clawed frog
The African clawed frog (Xenopus laevis, also known as the xenopus, African clawed toad, African claw-toed frog or the platanna) is a species of African aquatic frog of the Pipidae family. Its name is derived from the three short claws on each hind foot, which it uses to tear apart its food. The word Xenopus means "strange foot" and laevis means "smooth".
African clawed frogs can grow up to a length of 5 in (13 cm). They have a flattened head and body, but no tongue or external ears.
The species is found throughout much of Sub-Saharan Africa (Nigeria and Sudan to South Africa), and in isolated, introduced populations in North America, South America, and Europe. All species of the Pipidae family are tongueless, toothless and completely aquatic. They use their hands to shove food in their mouths and down their throats and a hyobranchial pump to draw or suck things in their mouth. Pipidae have powerful legs for swimming and lunging after food. They also use the claws on their feet to tear pieces of large food. They lack true ears but have lateral lines running down the length of the body and underside, which is how they can sense movements and vibrations in the water. They use their sensitive fingers, sense of smell, and lateral line system to find food. Pipidae are scavengers and will eat almost anything living, dying, or dead and any type of organic waste.
These frogs are plentiful in ponds and rivers within the south-eastern portion of Sub-Saharan Africa. They are aquatic and are often greenish-grey in color. Albino varieties are commonly sold as pets. “Wild type" African Clawed Frogs are also frequently sold as pets, and often incorrectly labeled as a Congo Frog or African Dwarf Frog because of similar colorings. They are easily distinguished from African Dwarf Frogs because African Clawed Frogs have webbing only on their hind feet while African Dwarf Frogs have webbing on all four feet. They reproduce by laying eggs (see frog reproduction). Also, the clawed frogs are the only amphibians to have actual claws used to climb and shred foods like fish or tadpoles. They lay their eggs from winter till spring during wet rainy seasons they will travel to other ponds or paddles of water to search for food.
The average life-span of these frogs ranges from 5–15 years with some individuals recorded to have lived for 20–25 years. They shed their skin every season, and eat their own shed skin.
Although lacking a vocal sac, the males make a mating call of alternating long and short trills, by contracting the intrinsic laryngeal muscles. Females also answer vocally, signaling either acceptance (a rapping sound) or rejection (slow ticking) of the male. This frog has smooth slippery skin which is multicolored on its back with blotches of olive gray or brown. The underside is creamy white with a yellow tinge.
Male and female frogs can be easily distinguished through the following differences. Male frogs are usually about 20% smaller than females, with slim bodies and legs. Males make mating calls to attract females, sounding very much like a cricket calling underwater. Females are larger than the males, appearing far more plump with hip-like bulges above their rear legs (where their eggs are internally located). While they do not sing or call out like males do, they do answer back (an extremely rare phenomenon in the animal world).
Both males and females have a cloaca, which is a chamber through which digestive and urinary wastes pass and through which the reproductive systems also empty. The cloaca empties by way of the vent which in reptiles and amphibians is a single opening for all three systems.
In the wild
In the wild, Xenopus laevis are native to wetlands, ponds, and lakes across arid/semiarid regions of Sub-Saharan Africa. Xenopus laevis and Xenopus muelleri occur along the western boundary of the Great African Rift. The people of the sub-Saharan are generally very familiar with this frog, and some cultures use it as a source of protein, an aphrodisiac, or as fertility medicine. Two historic outbreaks of priapism have been linked to consumption of frog legs from frogs that ate insects containing cantharidin. Wild Xenopus are much larger than their captive bred counterparts.
Xenopus laevis in the wild are commonly infected by various parasites, including monogeneans in the urinary bladder.
Use in research
Xenopus embryos and eggs are a popular model system for a wide variety of biological studies. 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. For a more comprehensive discussion of the use of these frogs in biomedical research, see the Wikipedia entry for Xenopus.
Xenopus has long been an important tool for in vivo studies in molecular, cell, and developmental biology of vertebrate animals. However, the wide breadth of Xenopus research stems from the additional fact that cell-free extracts made from Xenopus are a premier in vitro system for studies of fundamental aspects of cell and molecular biology. Thus, Xenopus is the only vertebrate model system that allows for high-throughput in vivo analyses of gene function and high-throughput biochemistry. Finally, Xenopus oocytes are a leading system for studies of ion transport and channel physiology.
Although X. laevis does not have the short generation time and genetic simplicity generally desired in genetic model organisms, it is an important model organism in developmental biology, cell biology, toxicology and neurobiology. X. laevis takes 1 to 2 years to reach sexual maturity and, like most of its genus, it is tetraploid. It does have a large and easily manipulated embryo, however. The ease of manipulation in amphibian embryos has given them an important place in historical and modern developmental biology. A related species, Xenopus tropicalis, is now being promoted as a more viable model for genetics.
Xenopus oocytes provide an important expression system for molecular biology. By injecting DNA or mRNA into the oocyte or developing embryo, scientists can study the protein products in a controlled system. This allows rapid functional expression of manipulated DNAs (or mRNA). This is particularly useful in electrophysiology, where the ease of recording from the oocyte makes expression of membrane channels attractive. One challenge of oocyte work is eliminating native proteins that might confound results, such as membrane channels native to the oocyte. Translation of proteins can be blocked or splicing of pre-mRNA can be modified by injection of Morpholino antisense oligos into the oocyte (for distribution throughout the embryo) or early embryo (for distribution only into daughter cells of the injected cell).
Extracts from the eggs of X. laevis frogs are also commonly used for biochemical studies of DNA replication and repair, as these extracts fully support DNA replication and other related processes in a cell-free environment which allows easier manipulation.
The first vertebrate ever to be cloned was an African clawed frog, an experiment for which Sir John Gurdon was awarded the Nobel Prize in Physiology or Medicine 2012 "for the discovery that mature cells can be reprogrammed to become pluripotent". 
Additionally, several African clawed frogs were present on the space shuttle Endeavour (which was launched into space on September 12, 1992) so that scientists could test whether reproduction and development could occur normally in zero gravity.
X. laevis is also notable for its use in the first well-documented method of pregnancy testing when it was discovered that the urine from pregnant women induced X. laevis oocyte production. Human chorionic gonadotropin (HCG) is a hormone found in substantial quantities in the urine of pregnant women. Today, commercially available HCG is injected into Xenopus males and females to induce mating behavior and to breed these frogs in captivity at any time of the year.
Model Organism Database for Xenopus
Xenopus laevis have been kept as pets and research subjects since as early as the 1950s. They are extremely hardy and long lived, having been known to live up to 20 or even 30 years in captivity.
African Clawed Frogs are frequently mislabeled as African Dwarf Frogs in pet stores. The astute pet owner will recognize the difference, however, because of the following characteristics:
- Dwarf frogs have four webbed feet. African Clawed Frogs have webbed hind feet while their front feet have autonomous digits.
- African Dwarf Frogs have eyes positioned on the side of their head, while African Clawed Frogs have eyes on the top of their heads.
- African Clawed Frogs have curved, flat snouts. The snout of an African Dwarf Frog is pointed.
They are as easy to take care of as fish.
As a pest
African Clawed Frogs are voracious predators and easily adapt to many habitats. For this reason, they can easily become a harmful invasive species. They can travel short distances to other bodies of water, and some have even been documented to survive mild freezes. They have been shown to devastate native populations of frogs and other creatures by eating their young.
In 2003, Xenopus laevis frogs were discovered in a pond at San Francisco's Golden Gate Park. Much debate now exists in the area on how to exterminate these creatures and keep them from spreading. It is unknown if these frogs entered the San Francisco ecosystem through intentional release or escape into the wild. San Francisco officials recently drained Lily Pond and fenced off the area to prevent the frogs from escaping to other ponds in the hopes they starve to death.
Due to incidences in which these frogs were released and allowed to escape into the wild, African Clawed Frogs are illegal to own, transport or sell without a permit in the following US states: Arizona, California, Kentucky, Louisiana, New Jersey, North Carolina, Oregon, Virginia, Hawaii, Nevada, and Washington state. However, it is legal to own Xenopus laevis in New Brunswick and Ohio.
The African clawed frog may be an important vector and the initial source of Batrachochytrium dendrobatidis, a chytrid fungus that has been implicated in the drastic decline in amphibian populations in many parts of the world. Unlike in many other amphibian species (including the closely related western clawed frog) where this chytrid fungus causes the disease Chytridiomycosis, it does not appear to affect the African clawed frog, making it an effective carrier.
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