Fig. 2

Schematic diagram showing the two major types of scleractinian development leading up to gastrulation. The complex corals typically have a minimal blastocoel before the start of gastrulation and only assume a spherical shape once gastrulation is complete. The robust corals, in contrast, develop a pseudo-blastopore (+) and pass through a hollow spheroidal stage before gastrulation begins. Endoderm = blue circles, mesoglea = purple lines, asterisk = blastopore. Modified from [6, 7]