Relative daughter cell volume and position of the division furrow in Tetrahymena

The relative daughter cell volume (RDCV) values for Tetrahymena pyriformis were determined at division on live cells. It was found that the anterior cell is generally larger than the posterior cell, and that the RDCV values are distributed in groups 5-6% apart. The RDCV value was found to be independent of predivision cell volume, indicating that the mother cell is divided into proportional volumes. The cells seem, however, not to assess volume directly but rather a parameter related to the cell volume. Furthermore, the RDCV value was found to increase during cell division, so that the final value is not reached until actual separation of daughter cells. It is suggested that the division furrow is positioned so that the area of the cell surface lying between the old oral apparatus and the posterior pole of the cell is divided into equal parts. It is further suggested that several alternative values of the RDCV are possible, only one of which is expressed in each cell. The early division furrow is placed anteriorly to its final position, and its location is adjusted during cytokinesis.