DIFFERENTIAL RESPONSES TO NEUTRAL RED UPTAKE OF MATING TYPE-I AND MATING TYPE-II CELLS IN PARAMECIUM-PRIMAURELIA .1. CELL-SIZE VARIATION

In Paramecium primaurelia the mating type I and mating type II cells react in a different way to the action of neutral red: the mating type II cells increase their size when stained with this vital dye; on the contrary, the mating type I cells show no variation in this respect. Since the neutral red, at a low extracellular concentration and for short exposure times, accumulates in lysosomes, it can be assumed that the mating type II cells possess a higher number of food vacuoles and also have more cytoplasmic binding sites for dye storage. A larger accumulation of neutral red inside the cell might cause the osmotic influx of water and the cell size increase observed in mating type II cells.