EXOGASTRULATION INDUCED BY CHILLING IN SEA URCHIN LARVAE

Publisher Website
Google Scholar
Abstract
Exogastrulation was induced by chilling in Strongylocentrotus intermedius, S. nudus, Pseudocentrotus depressus and Anthocidaris crassispina, but not in Hemicentrotus pulcherrimus. When early gastrulae were raised at low temperatures, no pseudopodia of secondary mesenchyme cells were formed, but invagination of the endodermal plate occurred normally. When later stage gastrulae having pseudopodia were chilled, the pseudopodia withdrew and the archenteron began to retract, resulting in exogastrulation. The exogastrulae were induced when larvae were raised in the presence of colchicine, vinblastine, cytochalasin B or cytochalasin C. Exogastrula formation on chilling may have been caused by microtubule depolymerization in the secondary mesenchyme cells and their pseudopodia. The fully invaginated archenteron of the late gastrula, even when chilled, remained within the blastocoel and did not evaginate. Effectiveness of low temperature treatment in inducing exogastrulation was probably related to environmental temperature at the breeding season.