Motility Events of Trichocyst Insertion in Paramecium tetraurelia*

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Abstract
Following electroshock-induced extrusion of its inserted trichocysts, P. tetraurelia rapidly begins replacement of the population of lost organelles. Light microscopy of the cortical insertion of new trichocysts reveals a series of characteristic motility activities. An uninserted trichocyst in the cyclotic flow of the cell appears to be captured and removed to the noncyclotic, subcortical regions. The trichocyst then makes a series of saltatory motions which apparently serve to transport it to the cortex, with proper orientation (tip first) for insertion. Trichocyst saltations end with either cortical insertion of the organelle, or return to cyclosis. If the trichocyst is inserted, it makes a series of unique pivoting movements around the motionless tip. This form of motility, termed wobble, continues for a short period of time. After cessation of wobble, the insertion of the trichocyst is apparently complete, since no further motility is observed. These observations showed that saltatory motility is the means for transporting trichocysts to the cortex for insertion, and demonstrated a motility of unknown significance (wobble) apparently associated with the process of cortical insertion.