Longitudinal microtubules and their functions during asexual reproduction inParamecium tetraurelia

Abstract
SUMMARY: Longitudinal microtubules appear inParamecium tetraureliawhen cells are ready to divide (ca.interfission age 0·9). They arise in the longitudinal cortical ridges between kineties and form, in each ridge, an incomplete circlet of 15–18 microtubules, disappearing 10–15 min after separation of the fission products (ca.interfission age 0·03–0·04). Vinblastine, colchicine, colcemid, mercaptoethanol, and cold treatments all result in loss of these microtubules, rounding up of the cells, and some suppression of cell division. The tubules are thought to play a role in cellular elongation, morphogenesis, and separation.