Change of contractile behavior in plasmodia of Physarum polycephalum during mitosis

Oscillations of ectoplasmic contraction in plasmodia of the myxomycete Physarum polycephalum growing on agar containing semidefined medium were studied to determine if the contractile force is altered during the synchronous mitosis. The halt of plasmodial migration during mitosis reported by others is caused by a decrease or cessation at slightly different times in the amplitude of ectoplasmic contractile oscillations in different areas of a plasmodium in mitosis resulting in an overall lack of coordination of endoplasmic flow throughout the plasmodium, thus temporarily halting migration. Possible physiological mechanisms linking a decrease in actomyosin contraction with the metaphase stage of mitosis are discussed.