Xenopus Development
How quickly do muscles develop in Xenopus?
Like those of most frog species, Xenopus eggs are actually fertilized outside of the mother. During mating, the male frog grasps the female trunk with its forelimbs, forming an embrace called amplexus (click the link for more information!). Fertilization occurs as the female releases the eggs, allowing the male to shed sperm onto them. After successful fertilization, notable stages of frog embryo development occur at the following timepoints: blastula formation at ~4 post-fertilization, gastrulation at ~10 hours, neurulation at ~18 hours, muscles respond to stimuli at ~96 hours, and heart begins beating ~118 hours (just under 5 days), with hatching (as a tadpole) occurring just 140 hours after fertilization1,2. This is remarkably rapid for a vertebrate animal compared to humans, wherein the first heartbeat occurs not until ~4 weeks after fertilization.