Correlation between ventral surface structures and local degeneration of cilia during conjugation in Paramecium

Correlation between cortical structures, such as the suture lines and the oral apparatus, and local degeneration of cilia during conjugation was investigated using aberrantly shaped cells which were produced by treating normal cells with 2 mM adenine for 24 h. Three types of aberrantly shaped cells were obtained: (1) proters, in which the oral apparatus is located at or near the posterior end of the cell and the preoral suture is much longer than that of a normally shaped cell' (2) opisthes, in which the oral apparatus is located extremely anteriorly, the preoral suture is very short and bent to the left, and the postoral suture and cytoproct are much longer than those of normally shaped cells; and (3) L-shaped cells, which are cells that have not separated at division and contain two buccal openings. The anterior member of the L-shaped cells (AML) has a long preoral suture and the posterior member of the L-shaped cell (PML) has a long postoral suture and cytoproct. The postoral field of AML and the preoral field of PML are missing. When these cells were mixed with normally shaped cells of the opposite mating type, the mating reaction took place between them. Scanning electron microscopic observation showed that, in all abnormally shaped cells, the degeneration of cilia always occurred along the full length of the preoral suture, regardless of its total length, and along the posterior right field of the buccal vestibulum, regardless of its location in the cell cortex. The localization of the degeneration of cilia, therefore, coincided with the position of the preoral suture and the buccal opening.