[8] Xenopus species are entirely aquatic, though they have been observed migrating on land to nearby bodies of water during times of drought or in heavy rain.

[8] During breeding season, the males develop ridge-like nuptial pads (black in color) on their fingers to aid in grasping the female.

[4][5] This animal is used because of its powerful combination of experimental tractability and close evolutionary relationship with humans, at least compared to many model organisms.

[4][5] Xenopus has long been an important tool for in vivo studies in molecular, cell, and developmental biology of vertebrate animals.

[13] In 1931, Lancelot Hogben noted that Xenopus laevis females ovulated when injected with the urine of pregnant women.

[14] This led to a pregnancy test that was later refined by South African researchers Hillel Abbe Shapiro and Harry Zwarenstein.

[17] The National Xenopus Resource of the Marine Biological Laboratory is an in vivo repository for transgenic and mutant strains and a training center.

Indeed, Xenopus was the first vertebrate animal for which methods were developed to allow rapid analysis of gene function using misexpression (by mRNA injection[22]).

[23] Moreover, the use of morpholino-antisense oligonucleotides for gene knockdowns in vertebrate embryos, which is now widely used, was first developed by Janet Heasman using Xenopus.

[25] Xenopus embryos have also provided a rapid test bed for validating newly discovered disease genes.

To test this hypothesis, the authors used Xenopus transgenesis, and revealed this genomic region drove expression of GFP in the hindgut.

Studies in Xenopus egg extracts have also yielded critical insights into the mechanism of action of human disease genes associated with genetic instability and elevated cancer risk, such as ataxia telangiectasia, BRCA1 inherited breast and ovarian cancer, Nbs1 Nijmegen breakage syndrome, RecQL4 Rothmund-Thomson syndrome, c-Myc oncogene and FANC proteins (Fanconi anemia).

This application has also led to important insights into human disease, including studies related to trypanosome transmission,[33] Epilepsy with ataxia and sensorineural deafness[34] Catastrophic cardiac arrhythmia (Long-QT syndrome)[35] and Megalencephalic leukoencephalopathy.

In just the last few years, Xenopus embryos have provided crucial insights into the mechanisms of TGF-beta and Wnt signal transduction.

[44] Cell division: Xenopus egg extracts have allowed the study of many complicated cellular events in vitro.

Because egg cytosol can support successive cycling between mitosis and interphase in vitro, it has been critical to diverse studies of cell division.

[46] More recently, using Xenopus egg extracts, it was possible to demonstrate the mitosis-specific function of the nuclear lamin B in regulating spindle morphogenesis[47] and to identify new proteins that mediate kinetochore attachment to microtubules.

[67] Physiology: The directional beating of multiciliated cells is essential to development and homeostasis in the central nervous system, the airway, and the oviduct.

[49] Because huge amounts of material are easily obtained, all modalities of Xenopus research are now being used for small-molecule based screens.

[70][71] Notably, frog embryos figured prominently in a study that used evolutionary principles to identify a novel vascular disrupting agent that may have chemotherapeutic potential.

The expression of genes can be reduced by a variety of means, for example by using antisense oligonucleotides targeting specific mRNA molecules.

DNA oligonucleotides complementary to specific mRNA molecules are often chemically modified to improve their stability in vivo.

MOs have proven to be effective knockdown tools in developmental biology experiments and RNA-blocking reagents for cells in culture.