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Xenopus (L., strange foot) is a genus of highly aquatic frogs native to Sub-Saharan Africa. There are 18 species in the Xenopus genus. They are known collectively as African Clawed Frogs or Platanna. [1] The best-known species belonging to this genus is Xenopus laevis, which is commonly studied as a model organism.
[edit] Key Characteristics of Xenopus [2]
- Description
- pupils of the eye are circular
- eyes are positioned on top of the head looking upwards
- flattened, somewhat egg-shaped body; streamlined and very slippery
- smooth skin with lateral line sensory organs that have a stitch-like appearance
- tympanum (eardrum), tongue and movable eyelids are lacking
- powerful, fully web toes; fingers lack webbing; these frogs are excellent swimmers
- three toes on each foot have conspicuous black claws
- they have no haptoglobin in their blood
- Behavior
- totally aquatic
- they are found in lakes, rivers, swamps, ponds and man-made reservoirs
- during times of drought, they have been known to migrate on land to near-by bodies of water
- adult frogs are both predators and scavengers
- since they do not have a tongue, the forelimbs aid in the feeding process
- frogs do not have a vocal sac and calling occurs from underwater
- amplexus or mating embrace is inguinal, which means that the male grasps the female around her waist
- during breeding season, the males have ridge-like nuptial pads (black in color) on the fingers to aid in grasping the female
- females have distinct skin folds around the vent (cloaca)
- they are crepuscular or active during the twilight hours
- widely used in laboratory research
[edit] Xenopus research models
Xenopus are a popular model system for gene and protein expression and knockdown studies. At 1 mm diameter, Xenopus oocytes are very large cells which are easy for scientists to culture and use in experiments. RNA from other organisms can be injected into the large oocytes and the resulting expression studied via molecular biology techniques or through electrophysiology experimentation. Gene expression can be knocked down or splicing modified using Morpholino antisense oligos injected into Xenopus oocytes (for whole-body effects) or early embryos (for effects in the daughter cells descended from the injected cell). Cytoplasmic extracts made by centrifuging Xenopus eggs or embryos (allowing direct addition or depletion of proteins) can recapitulate a wide range of complex cellular processes including nuclear envelope formation, DNA replication and spindle assembly.
While Xenopus laevis is the most commonly used species for developmental biology studies, genetic studies can be complicated by their pseudotetraploid genome. Xenopus tropicalis provides a simpler model for genetic studies, having a diploid genome. Morpholino knockdown techniques are also used in X. tropicalis to probe the function of a protein by observing the results of eliminating the protein's activity, as was done in a screen [1] [2] of X. tropicalis genes published in 2006.
X. laevis is often used as a low-tech pregnancy test; for details, see the species account.
[edit] References
- ^ African Clawed Frog Wiki
- ^ Passmore, N. I. & Carruthers, V. C. (1979). South African Frogs, p.42-43. Witwatersrand University Press, Johannesburg. ISBN 0854945253.
[edit] External links
- Xenbase ~ A Xenopus laevis and tropicalis Web Resource
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