SPATIAL AND TEMPORAL PATTERNS OF MITOSIS IN THE CELLS OF THE AXIAL POLYP OF THE REEF CORAL ACROPORA CERVICORNIS.

The fluorescent stain DAPI was used to observe mitoses in the endoderm and the calicoblastic ectoderm of the axial polyp of the reef coral Acropora cervicornis. A diel periodicity in the mitotic index (defined as the percentage of cells in some stage of mitosis) of each tissue occurred with a maximum of about 2% at midnight and a minimum of 0.5% at midday. Dividing cells were located from the tip of the column (when the polyp was contracted into the calyx) to 10 mm proximal to this point suggesting that there is no narrow zone of proliferating cells. The magnitude of the mitotic indices of these tissues suggests that it may account for the observed daily growth rate of ca. 300 µm in the axial polyp.