SURFACE CONTRACTILE ACTIVITY OF THE TUBIFEX EGG - ITS RELATIONSHIP TO THE MEIOTIC APPARATUS FUNCTIONS

The dependence of surface contractile activity (deformatin movement: DM) on the meiotic process in the fertilized Tubifex egg was examined with colchicine and dinitrophenol (DNP). The normal DM occurred at the time of the formation of the first and second polar bodies, during which the egg shows groove‐forming activity on the surface of the animal hemisphere and the equatorial regions. Grooves invariably appeared first on the equatorial surface, then on the animal hemisphere. A scanning electron microscopic observation revealed that the surface deformation of the animal hemisphere began concurrently with the appearance of proximal constriction of the cytoplasmic bulge for the polar body. DNP of 2.5 × 10−5 M did not disturb the meiotic process but inhibited equatorial grooving. The animal hemisphere grooving in these eggs took place on the same schedule as for normal eggs. The number of microfilaments per unit area of the egg surface apparently decreased after DNP‐ treatment; the organization of microfilaments in the cortical layer was more heavily influenced at the equaorial region than in the animal hemisphere. Colchicine of 4 × 10−3 M destroyed the meiotic apparatus and completely prevented the grooving of the animal hemisphere. The equatorial grooving proceeded normally in these colchicine‐treated eggs. From these results, it is strongly suggested that there are regional differences in the contractile mechanism of the egg surface and that the animal hemisphere grooving is closely related to the presence of the meiotic apparatus while the equatorial grooving is independent of it. Copyright © 1979 Wiley‐Liss, Inc., A Wiley Company