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African Clawed Frog

Taxonomy

Order: Anura
Family: Pipidae
Genus/species: Xenopus laevis

Description

This is a unique family of frogs that lack a tongue and a visible ear. The males also lack vocal cords. Instead of moveable eyelids, a horny, transparent covering protects their eyes. The body is flattened and the head is wedge-shaped and smaller than the body.

The African clawed frog's front limbs are small with unwebbed fingers that are used to push food into the mouth. Its hind legs are large and webbed and the three inside toes on either foot have claws, this is where they get their common name. However, while they may look like claws, they are not true claws but cornified tips.

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.

African clawed frogs have the ability to change their appearance to match their background. They can become dark, light, or mottled. They also have a lateral line system that is very sensitive to movement of water.

Males weigh two ounces (60 grams), and are about two to 2.5 inches (5 to 6 cm) long. Males also lack a vocal sac, which most male frogs have. Females are much larger. They weigh seven ounces (200 grams) and are about four to 4.5 inches (10 to 12 cm) long. Females also have cloacal extensions at the end of their abdomen.

Distribution and Habitat

These frogs are found along the African Rift Valley south of the Sahara in east and southern Africa. They are also found in South Africa and Namibia and Angola in western Africa. As an invasive pest species they are now found in freshwater areas all over the world.

They prefer warm stagnant pools, and quiet streams; they are rarely found in running streams. They can tolerate wide variations in water pH, but metal ions are toxic. They thrive in temperatures from 60 to 80 degrees Fahrenheit. They leave the water only when forced to migrate.

Diet in the Wild

African clawed frogs are carnivorous and eat anything they can find. They are scavengers and eat living, dead, or dying arthropods and other pieces of organic waste including aquatic insect larvae, water insects, crustaceans, small fish, tadpoles, worms, and freshwater snails.

They have a voracious appetite and will attack anything that passes in front of it. They use extremely sensitive fingers, an acute sense of smell, and lateral line system to locate food and then use a hyobranchial pump to suck food into their mouths. The tadpoles are exclusively filter feeders.

Zoo Diet

They are fed earthworms two to three times a week.

Reproduction

These frogs are sexually mature in ten to 12 months. Mating can take place during any time of year, but is most common from early spring to late summer, depending on location, and may take place up to four times a year.

Males vocalize, even though they lack vocal cords, to attract females. Instead they use rapid muscle contractions in their throat to produce a type of clicking noise. The female will then either respond with an acceptance call or a rejection call.

Mating usually takes place at night where they engage in pelvic amplexus, in which the males clasp females about the pelvic region.

Eggs are about .04 inches (.1 cm) in diameter. Sticky jelly around the eggs causes them to adhere to objects underwater like sticks, stones, and other substrate. Females lay 500 to 2,000 eggs at one time and 2,000 to 8,000 eggs per year.

Eggs hatch within one week and tadpoles are about .16 inches (.4 cm) long. The total change from egg to small frog takes about six to eight weeks. Adults exhibit no parental care.

Life Span

This is a rather inactive and hardy creature that may live up to 15 years.

Status

This species of African clawed frog is neither threatened nor endangered. Presumably as a result of pet release, they have been introduced into Orange and San Diego counties in California, Arlington, Virginia, and Delaware, where they are now pests, devouring native wildlife such as fish, frogs, tadpoles.

These frogs have been used extensively as a laboratory research animal, mostly in the field of vertebrate embryology because females are prolific egg layers and the embryos are transparent.

Fun Facts

During the 1940s, female African clawed frogs were injected with urine of a female human. If the human was pregnant, then the injected frog would start producing eggs.

This was the first vertebrate cloned in the laboratory. They also produce a type of antibiotic, Magainins, in their skin that heals wounded skin rapidly. Magainins are antifungal, antiparasitic, and antiviral. This is probably very useful in the stagnant, microbe-filled waters in which this species lives.

At times when the pond dries up, this frog burrows in the mud and may lie dormant for up to a year. During the rainy season it can crawl long distances to another pond, but it can not hop.

It spends most of its time underwater, coming to the surface to breathe. Respiration is predominately through its well-developed lungs; there is little cutaneous respiration.

Source of Information

All or part of this information was provided by the Animal Diversity Web and Museum of Zoology of the University of Michigan. It appears here with their permission. The original author of this information was Nathan Garvey.

For more information, including references, see the Animal Diversity Web account for this species, here: http://animaldiversity.ummz.umich.edu/ site/ accounts/ information/ Xenopus_laevis.html.