African Clawed Frog

frogs in a tank
Frogs in the National Xenopus Resource at the MBL. Credit: Daniel Cojanu

African clawed frogs (Xenopus) are aquatic frogs with small, wedged-shaped heads and flattened bodies. They have smooth skin, which is often mottled and olive to brown color on their backs and yellow-white on their bellies. Their front feet are small and unwebbed, and used to push food into the mouth. The hind legs are large and webbed with three sharp, black “claws” on the inner toes. These are not true claws, but instead cornified tips. Xenopus eyes are located at the top of the head and have no lids.  Xenopus have a lateral line system sensitive to vibrations, which allows them to detect prey and avoid predators in murky water. Xenopus can produce thousands of offspring from a single clutch of eggs.

The frog species Xenopus laevis and Xenopus tropicalis, are key model organisms for biomedical research. Historically Xenopus has been an important model for developmental biology research. Additionally, they regenerate tissues, organs, and limbs, making them an important model for regenerative medical research. X. tropicalis is the only Xenopus species to have a diploid genome, making it ideal for genome editing.

Scientific Name: Xenopus

Type: Amphibia
Habitat: A wide variety of both natural and manmade habitats including lakes, ponds, streams, wetlands, and canals.
Range: Natively from the African Rift Valley, as well as in South Africa, Namibia and Angola. As an invasive species, Xenopus are found in freshwater areas all over the world
Life Span in the Wild: 15+ years
Size: Males: 2 - 2.5 in (5 - 6 cm); Females: 4 - 4.5 in (10 - 12 cm)
Weight: Males 2 ounces (60 grams); Females: 7 ounces (200 grams)
Diet: Scavenger of living, dead or dying arthropods. insect larvae, crustaceans, small fish, tadpoles, worms and freshwater snails
Status: Species of Least Concern

They are widely used in research thanks to a powerful combination of experimental tractability and a close evolutionary relationship with humans.


Xenopus Tropicalis in the NXR Credit: James Parente
Xenopus in the NXR at the MBL. Credit: James Parente

Xenopus and the MBL

The MBL is home to the National Xenopus Research (NXR), a national stock center for X. laevis and X. tropicalis and a training center for advanced technologies. Housed in the MBL’s Loeb Laboratory, the NXR is a cornerstone of the Eugene Bell Center for Regenerative Biology and Tissue Engineering. The NXR provides a facility for maintaining and shipping genetic stocks, new experimental tools, husbandry techniques, and meeting other needs of the Xenopus research community.

The NXR is home to more than 10,000 frogs, including many mutant and transgenic lines. These animals are utilized by MBL’s year-round and visiting researchers for a wide variety of research topics including modeling genetic diseases, sex determination, as well as developmental and evolutionary biology.

Learn more about the NXR