Cortical ultrastructure of Paramecium aurelia. Studies on isolated pellicles.

Abstract

Two methods have been devised for the isolation of large quantities of purified pellicles (cortical layers) of Paramecium aurelia. Pellicles isolated by both procedures, when examined by electron microscopy, were found to contain ciliary basal bodies, two types of cortical membranes, ribbons of microtubules, kinetodesmal fibers, and elements of the infraciliary lattice system. By electron microscopy, the extent of preservation of the various cortical structures when pellicles are isolated by each method has been characterized. Pellicles isolated in both ways have been utilized to investigate cortical morphology of Paramecium. Both phase-contrast and electron microscopic observations have been made. Many new ultrastructural features were observed and are reported herein. An interesting result of this study is the discovery in stock CD that the structure of cortical territories (the territory is the functional unit of cortical morphogenesis and physiology) may vary within a single organism. Features which show variation include number of parasomal sacs, microtubular ribbons, and basal bodies (and therefore cilia) per territory, number of microtubules per ribbon, and length of kinetodesmal fibers. The possible significance of these variations, with respect to territory replication, is discussed. In addition, preliminary observations on the solubility of various cortical organelles in the presence of a number of protein-denaturing agents are reported.