The Role of Cell Adhesion in the Differentiation of Mesendodermal Tissues in the Starfish, Asterina pectinifera

The role of cell-to-cell adhesion in the early embryogenesis of the starfish Asterina pectinifera was studied by using concanvalin A (ConA), an agent known to weaken cellular contact by binding to glycosides at the cell surface. The major change in morphology was a diminution in the volume of the endodermal tissues (the digestive tract) of the treated larvae. It was found by pulse treatment that this effect of ConA was stage-specific, and that the effective period corresponded to the stage when blastomeres become more cohesive. The number of cells in the mesodermal tissues, however, was relatively constant while the volume of the endodermal tissue varied considerably. It was suggested that cell-to-cell adhesion during this stage is involved in the allocation of endodermal tissues. In contrast, mechanisms other than cell adhesion were considered to be important for the differentiation of the mesodermal tissues.