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Freeze fracture study of the plasma membrane of the marine loricate ciliate Eufolliculina uhligi : morphology and distribution of intramembrane particle aggregates in the swarmer and in the lorica secreting cell
Author(s) -
Mulisch Maria,
Nielsen Jürgen,
Hausmann Klaus
Publication year - 1989
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1111/j.1768-322x.1989.tb00871.x
Subject(s) - biology , vesicle , ciliate , biophysics , paramecium , exocytosis , membrane , microbiology and biotechnology , anatomy , biochemistry , ecology
Our freeze‐fracture study has revealed the presence of two types of intramembrane particle (IMP) aggregates in the somatic plasma membrane of Eufolliculina uhligi : rectangular particle arrays and rosettes. Their morphology and distribution differ in the motile and in the lorica secreting stage. Rectangular particle arrays occur to the left of the kineties. They are not very obvious in the swarmer, but increase in size and number during lorica formation. We discuss whether they are involved in the contractility of this ciliate. Rosettes occur to the right of the kinetics where they mark attachment sites of extrusive vesicles at the plasma membrane of the swarmer. No annulus‐like structure as e.g. in Tetrahymena mucocysts and Paramecium trichocysts has been found in the membrane of these vesicles. The rosettes consist of 10‐nm particles and lack an outer ring. Vesicle membrane and plasma membrane appear to remain separated during exocytosis. In the course of lorica secretion, the number of rosettes continuously decreases, following an anterior‐posterior gradient. This indicates that new insertion of extrusive vesicles from intracellular stores occurs preferably at the anterior of the cell.