How Paramecium cells die under a cover glass?

抄録

The dying process of Paramecium tetraurelia cells under a cover glass without supporting pillars was described. The initiation of the process was defined by the cessation of swimming, and the termination by cell rupture. The process required 6 min on average, ranging from 1 to 11 min. The first symptom of death was the formation of a small bleb, a local swelling of the outer cell membrane. The number of blebs increased, each bleb grew, and neighboring blebs fused to form a larger bleb. By supplying water, the blebs disappeared only when their size and numbers were relatively small, indicative of a commitment point to death. Finally the outer membrane and then the inner membrane were broken, and the cytoplasmic contents flew out. Until the last moment of the cell rupture, and sometimes even after that, ciliary beating was observed somewhere locally on the cell membrane. Among the cilia, those at the cytopharynx were the first to stop beating so that food vacuole (FV) formation stopped somewhat earlier than the cellular disorganization. Cessation of the contractility of contractile vacuoles (CVs) occurred a little bit later on average than the cessation of FV formation. Anterior and posterior CVs were not related to each other in the timing of loss of contractility and in the preceding pulsating cycles. Finally, we calculated the physical pressure to burst the cell at about 950 atm and estimated the actual pressure to be at 470～2,000 atm.