A L. variegatus late gastrula, viewed from the ventral (oral) side. Courtesy of Dr. Chuck Ettensohn, Carnegie-Mellon Univ.
The sea urchin embryo was one of the first systems in which gastrulation was studied using time-lapse cinemicrography, worked pioneered by Tryggve Gustafson and colleagues in Sweden. The simple organization of the sea urchin gastrula, combined with its transparency make it ideal for elucidating the basic cellular principles of gastrulation. The next few pages provide an overview of the various stages of sea urchin gastrulation, and some of the cellular mechanisms that underlie them.