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).

The range of this species is unclear following the removal from Xenopus victorianus from X. laevis. For the purposes of this assessment we have assumed that all animals from southern Angola, Zambia, Malawi and Mozambique southwards (including in almost all of Zimbabwe, Botswana, Namibia, South Africa, Lesotho and Swaziland) belong to X. laevis. In addition we treat all animals in Nigeria, Cameroon, Central African Republic, and the Democratic Republic of Congo west of 28ºE as belonging to X. l. sudanensis. Records from Tanzania, Kenya, Uganda, Rwanda, Burundi, Sudan and the Democratic Republic of Congo east of 28ºE refer to this X. victorianus. There is an isolated record from Gabon (M. Beier pers. comm. January 2006).

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.

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).

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

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

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

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.

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).

Animal / parasite / endoparasite
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).

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.

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.

Range lifespan

Status: wild: 16 (high) years.

Range lifespan

Status: captivity: 20 (high) years.

Average lifespan

Status: captivity: 8.8 years.

Average lifespan

Status: captivity: 15.0 years.

Maximum longevity: 30.3 years (captivity) Observations: Despite its short longevity, this animal does not show explicit signs of ageing (Brocas and Verzar 1961). Reproductive senescence has not been demonstrated, but growth rates appear to slow down with age. An increased tensile strength in tendon collagen with age, a frequent marker of ageing in mammals, as been reported (Kara 1994).

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

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).

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).

Peptides protect from bacterial infection: African clawed frog
 

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 cells respond to hormones: African clawed frog
 

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.

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 12 barcode sequences available from BOLD and GenBank.  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.


Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
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

United States

Rounded National Status Rank: NNA - Not Applicable

Rounded Global Status Rank: G5 - Secure

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).

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).

Population

Population Trend

Not threatened.

Major Threats

Comments: May have declined recently in southern California, due possibly to drought and fish predation (McCoid et al. 1993).

Conservation Actions

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).

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

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).

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).