 However, instead of a primitive streak there is a circular blastopore surrounded by an embryonic disc.Surprisingly, extension starts only after involution at the blastopore is concluded, demonstrating that these important movements can be dissociated from gastrulation itself.Her analyses revealed extensive modularity in the developmental processes that guide the blastopore closure and notochord elongation in amphibians, features that correlate with reproductive modes and ecological adaptations.