Differences in Macronuclear DNA Content Characterizing the Reactive Populations of Paramecium primaurelia Complementary Mating Types

Abstract

Summary By assuming that the modes of cell growth are accounted for mating type determination and expression (Crippa Franceschi 1981), the macronuclear Feulgen-DNA content of the reactive populations of Paramecium primaurelia mating type I (stock 90 and stock P) and mating type II (stock 90) has been determined by fluorescence cytophotometry. The results show that significant differences occur between the complementary mating type populations; particularly, the mating type II cells are characterized by a mean DNA content lower than that of the mating type I cells of the same stock, the greatest mean value being shown by the stock P cells. Furthermore, when the mating reactivity is maintained, the persistence of significant differences between the n-iean DNA contents of the complementary mating types is found. The implications with the hypothesis of the “cell growth modes” are discussed.