Name: African clawed frog (Xenopus laevis)
Range: Sub-Saharan Africa (Angola, Botswana, Cameroon, Central African Republic, Gabon, Lesotho, Malawi, Mozambique, Namibia, Nigeria, South Africa, South Sudan, Swaziland, The Democratic Republic of the Congo, Zambia, Zimbabwe.
Diet: Opportunistic predators, consuming both live and dead matter.
Conservation Status: IUCN – Least Concern
The African clawed frog is an aquatic species that is very common throughout its native range. It prefers shallow warm waters and tends to avoid areas of high flow. During periods of drought, the frogs may lie dormant in the mud for up to a year. Though aquatic, the frogs may crawl to new habitats during the rainy season.
The frogs appear dorsally compressed, with a very flat head. They do not possess eyelids, but instead have a tough, transparent, layer that covers and protects the eyes. They lack external ears. The “claws” that give these frogs their name are not really claws, but rather toughed skin on the finger tips. The colouration varies significantly between individuals, and can be changed for camouflage purposes, but it is typically mottled, with patches of olive-green and brown. The species displays sexual dimorphism, with the females being much larger than the males.
X. laevis are voracious feeders and will predate on any organism that is small enough to be swallowed. They detect prey using their sensitive fingertips, keen sense of smell and their lateral line (A vibration sensitive line in the animal’s skin). Prey are consumed by scooping them into their mouth with both hands, and by utilising a hypobranchial pump to suck prey into the mouth.
Though they lack external ears, this species still engages in vocalisations during courtship. The male signals his presence via vocalisations, produced by contractions of their throat muscles (They do not possess vocal cords). Any females nearby will signal their interest, or disinterest, with an appropriate vocalisation. Breeding typically occurs at night, with the female laying between 500-2,000 eggs per night, and up to 8,000 per year. The eggs hatch within a week and the tadpoles complete metamorphosis within 2 months.
Historically, Xenopus has been a very important animal as a model organism in research. They are particularly useful in the fields of developmental biology, toxicology and neurobiology. They were also the first vertebrate animal to be cloned successfully. Perhaps the most widely known use of Xenopus for medical purposes, is their widespread use as one of the first pregnancy tests. Female frogs were injected with the urine of a human female. If the woman was pregnant, the frog would produce eggs.
These frogs are so useful, they have been shipped all over the world. They have escaped captivity(or been released) on occasion, and this has led to them establishing invasive populations worldwide. This phenomenon has been suggested as a means by which the amphibian chytrid fungus (Batrachochytrium dendrobatidis) may have been transported out of Africa to infect populations globally, however a 2015 study has shown that infected Xenopus may not transmit the disease to native populations, despite cohabiting the same habitats.