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Xenopus laevisAfrican Clawed Frog

By Nathan Garvey

Geographic Range

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)

Habitat

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)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

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)

  • Sexual Dimorphism
  • female larger
  • Range mass
    60 to 200 g
    2.11 to 7.05 oz
  • Range length
    5 to 12 cm
    1.97 to 4.72 in
  • Average basal metabolic rate
    0.012 W
    AnAge

Development

Reproduction

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

Lifespan/Longevity

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.

Behavior

Xenopus laevis is a rather inactive creature. It is incredibly hardy and can live up to 15 years. At times the ponds that Xenopus laevis is found in dry up, compelling it, in the dry season, to burrow into the mud, leaving a tunnel for air. It may lie dormant for up to a year. If the pond dries up in the rainy season, Xenopus laevis may migrate long distances to another pond, maintaining hydration by the rains. It is an adept swimmer, swimming in all directions with ease. It is barely able to hop, but it is able to crawl. It spends most of its time underwater and comes to surface to breathe. Respiration is predominantly through its well developed lungs; there is little cutaneous respiration

(Kaplan, 1995; Simmonds 1985)

Food Habits

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

Economic Importance for Humans: Positive

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.

Economic Importance for Humans: Negative

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.)

Conservation Status

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.

Contributors

Nathan Garvey (author), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

diurnal
  1. active during the day, 2. lasting for one day.
drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

scavenger

an animal that mainly eats dead animals

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

year-round breeding

breeding takes place throughout the year

References

Avila, Vernon L. and Frye, Patricia G. 1978. Feeding behavior of the African Clawed frog (Xenopus laevis Daudin):effect of prey type. Journal of Herpetology 12(3).

Beck, Alan. 1994. http://gto.nsca.uiuc.edu/pingleto/xenopus.html

Kaplan, Melissa. 1995. Natural History of the Upland Clawed Frog. http://www.sonic.net/~melissk/xenopus.html

Kelley, Darcy B. 1998. http://www.cc.columbia.edu/cu/biology/faculty/kelley.html

Nieukoop, P.D and Faber, J. 1994. Normal Table of Xenopus Laevis (Daudin). Garland Publishing, Inc., New York and London

Simmonds, Mark P. 1985. African Clawed toad survey. British Herpetological Society Bulletin No. 13.

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