Cleavage furrow formation in a telolecithal egg ( Loligo pealei) : III. Cell surface changes during cytokinesis as observed by scanning microscopy

Abstract

During cytokinesis of the telolecithal egg of the squid the blastodisc undergoes a sequence of surface changes in the region of the future furrow. First the surface is “gathered” into a line of microvilli which are oriented along the axis of the forming furrow; then as the furrow deepens these microvilli tend to fuse and form longitudinal folds in the base of the furrow. As the opposing edges of the future blastomeres come into contact there are numerous linearly arrayed spheroidal bodies associated with the area of contact. When the new blastomeres come into close contact, numerous microvilli connect the two cells at their upper edges. Blastomeres in the central portion of the blastoderm appear to divide by a “contractile ring” as described for holoblastic cleavage of other animal eggs. It is speculated that the “new” surface between the forming blastomeres arises, at least in part, from preexisting surface gathered during the early phases of cytokinesis.