A comparative study of the concrement vacuole of certain endocommensal ciliates—a so-called mechanoreceptor

Abstract

The concrement vacuole is a distinguishing cytoplasmic characteristic of ciliates of the families Buetschliidae and Paraisotrichidae. The vacuoles of the various species have some structural features in common; however, the distinctive morphologic qualities possessed by them permits their classification into two types: CV-1 (Buetschliidae) and CV-II (Paraisotrichidae). Two of the common features are: (a) oval concretions which give a positive reaction for calcium when subjected to the Alizarin red S test and which, in thin sections, display a laminated pattern, and (b) ciliary rootlets. The basic unit of each rootlet appears tubular and measures about 220–240 Å in diameter. These rootlets are derived from the kinetosomes of a group of presumably specialized cilia and together define a part (Paraisotrichidae) or all (Buetschliidae) of the vacuole's boundary. Speculation is offered concerning possible modes by which the concrement vacuole could function as a statoreceptor. The kinetosomes which constitute the somatic infraciliature are attached to a subtending fibrous band whose constituent filaments are 60–70 Å in diameter. This fibrous band, in addition to dividing the cytoplasm of both families into ectoplasm and endoplasm, partially encircles the CV-II type concrement vacuole. The cytopharyngeal armature is also composed of ciliary rootlets whose individual units are 220–240 Å in diameter. Together these units form a hexagonal pattern. There is no anatomical association between the components of the cytopharyngeal armature and the vacuole. The cytoplasm of organisms from both families contains gastrioles, a contractile vacuole, a large complement of rough variety of endoplasmic reticulum, and a host of vesicles and agranular cisternae. The plasma membrane is endowed with a fuzzy coat; it is particularly prominent on organisms of the family Buetschliidae. This coat is PAS-positive, a reaction which is not abolished by prior treatment with α -amylase.