Journal of Cell Science, Vol 16, 499-517, Copyright © 1974 by Company of Biologists

Submitted on May 6, 1974

Cytokinesis in the Heliozoan Actinophrys Sol

¹ Department of Zoology, The University, St Andrews, Fife, Scotland and Institut für Biologie 3 der Universität, 74 Tübingen, Auf der Morgenstelle 28, German Federal Republic

A study of cytokinesis in the heliozoan Actinophrys sol has been made using low-temperature treatments, antimitotic drugs, cytochalasin B, light microscopy and electron microscopy. It reveals that microtubular axopodia remain extended during cell division and play a major role in it.

Data indicate that when organisms are attached to the bases of culture dishes the normal locomotive mechanism of the presumptive daughter cells pulls them apart. However, when Actinophrys are floating freely in their culture medium, they are still able to undertake division. In this situation interactions between axopodia from opposite daughter cell bodies appear to facilitate the movement apart of the prospective daughter cells.

The present study and other published accounts indicate that a type of cytokinesis exists which is not explicable in terms of the ‘contractile ring’ or ‘fusing vesicle’ theories. To account for these observations a ‘barge pole’ model of division is suggested.

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