Cell-to-cell contact by locally differentiated surfaces in conjugation of Blepharisma

Local functional differences of the cell surface were investigated in the formation of cell unions in conjugation of Blepharisma intermedium. When cells of this ciliate are treated by the gamone (the conjugation-inducing substance) of the complementary mating type, they first unite by cilia and then more intimately by the direct contact of cell bodies. The ciliary union was found to be formed by a specific contact between two morphologically distinguishable surfaces, the adoral zone of membranelles (AZM) of one cell and the anterior extension of the undulating membrane (extUM) of the other. The AZM gains the capacity to unite first and the extUM next. The extUM of gamone-treated cells sticks not only to the AZM but also to glass and some other artificial substrata under some conditions. These stickings are inhibited by cycloheximide which also inhibits the ciliary union. The role of specific contact between AZM and extUM in the cell recognition is discussed.