Development of Xenopus laevis

Development of Xenopus laevis
History as a model organism

Scientists have used Xenopus laevis, an African clawed frog, to understand embryogenesis and development since the 1800s. Prior to the 1930s, researchers would go out in the spring during the breeding season, do as many experiments with the eggs as possible, and then analyze results for the rest of the year until the next spring.
However, in the 1930s, it was discovered that if urine from a pregnant woman was injected into a frog, a hormone called human chorionic gonadotropin (hCG) would cause the frog to ovulate, even out of season. It wasn't long before this technique was used as a standard to detect pregnancy.



Tails have elongated slightly and pigmentation is more prominent.
(02/16/18)


While this was an effective human pregnancy test for a few decades, it was an eventually replaced by the immunoassays used today. However, hCG continues to be used to induce ovulation in Xenopus, allowing developmental biologists to conduct experiments year round. The female frog can stay alive, and fertilization can be induced many times.



View of a single tadpole.
Nostrils are developing more and stomach is more prominent.
(02/21/18)




The embryos now have the characteristic tadpole shape as their anterior end widens and posterior end elongates.
The developing stomach is visible.
Eyes are becoming more sophisticated in structure.
The heart is barely visible near the stomach.
Nostrils are visible.
(02/19/18)



Larval stage, with jelly coat still present.
(02/14/18)



Yolk has significantly reduce.
The tail has also elongated and the dark spots are eyes.
The cement gland is reddish in color.
(02/15/18)



Lone tadpole in a vertical orientation.
Groups of them would do this at a time, hanging from the surface of the water.
(02/16/18)

This ease of availability to eggs is just one reason that Xenopus is an ideal model for development. The eggs are large enough to see even the earliest stages of development, and because they are covered in a protective jelly instead of a shell, there is an unobstructed view of these processes. There is also a high level of translatability between the frog and human developmental genetics.



This series will explore the development of Xenopus laevis, by way of fertilization, cleavage, gastrulation, neurulation, organogenesis, and metamorphosis from tadpole to adult.