African clawed frog
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| Xenopus laevis Daudin, 1802 |
The African clawed frog (Xenopus laevis, also known as platanna) is a species of South African aquatic frog of the genus Xenopus. It is up to 12 cm long with a flattened head and body but no tongue. Its name derives from its three short claws on each of its hind feet, which it probably uses to stir up mud to hide it from predators.
Although X. laevis is not blessed with the short generation time and genetic simplicity generally desired in genetic model organisms, it is an important model organism in developmental biology. X. laevis takes 1 to 2 years to reach sexual maturity and, like most of its genus, it is tetraploid. However, it does have a large and easily manipulable embryo. The ease of manipulation in amphibian embryos has given them an important place in both historical and modern developmental biology. A related species, Xenopus tropicalis, is now being promoted as a more viable model for genetics. Roger Wolcott Sperry used X. laevis for his famous experiments describing the development of the visual system. These experiments led to the formulation of the Chemoaffinity hypothesis.
Xenopus oocytes provide an important expression system for molecular biology. By injecting cDNA or cRNA into the developing oocyte, scientists can study the protein products in a controlled system. This allows rapid functional expression of manipulated cDNAs (or cRNA). This is particularly useful in electrophysiology, where the ease of recording from the oocyte makes expression of membrane channels attractive. One challenge of oocyte work is eliminating native proteins that might confound results, such as membrane channels native to the oocyte. Translation of proteins can be blocked or splicing of pre-mRNA can be modified by injection of Morpholino antisense oligos into the oocyte (for distribution throughout the embryo) or early embryo (for distribution only into daughter cells of the injected cell).
X. laevis is also notable as having been a standard method of pregnancy testing. Human chorionic gonadotropin is a hormone found in substantial quantities in the urine of pregnant women; when injected into the female X. laevis it induces them to lay eggs.
[edit] African clawed frogs as pets
In recent years African Clawed Frogs have become popular pets. It has been found that there is a strong connection between the international trade of X. laevis and a global decline in frog populations due to the spread of chytridiomycosis [1].
Often confused with the much smaller African Dwarf Frog, the clawed frog has webbing on its back feet but has four unwebbed fingers on each front foot. Females grow to an average of 5 inches (130 mm) snout to vent; males are generally smaller, around 3.5 to 4 inches (90 to 100 mm). They are social frogs and should be kept with others of their species. Highly carnivorous, they will attack and eat any fish kept with them. African Clawed Frogs should be kept in 10 US gallons of water per frog, and are completely aquatic. A well fitting lid is required for keeping clawed frogs, as they can leap out of most tank set-ups. As with fish-keeping, it is necessary to closely monitor water quality and change water weekly in order to keep these frogs healthy. If properly cared for, African Clawed Frogs can live over 15 years. As with African Dwarf Frogs, Clawed Frogs are sensitive to the presence of chlorine and chloramines in the water, and it is essential that a reliable method of dechlorination is used before water is added to a Clawed Frog tank.
A common mis-labeling in pet shops is the "African Dwarf Clawed Frog". Dwarf Frogs and Clawed Frogs are two independent species.
[edit] References
- Tinsley et al (2004). Xenopus laevis. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006. Database entry includes a range map and justification for why this species is of least concern
[edit] External links
- Webcam of an aquarium which is inhabited by four African clawed frogs
- Wildlife Trade and Global Disease Emergence
- Xenbase A Xenopus laevis and X. tropicalis web resource.
- All About African Clawed Frogs Resources and lots of Information for keeping ACF's as pets.
