CYTOPLASMIC BACTERIA-LIKE ENDOSYMBIONTS IN EUPLOTES CRASSUS (DUJARDIN) (CILIATA HYPOTRICHIDA)

Abstract

SUMMARY Seventeen stocks of Euplotes crassus (Dujardin) (Ciliata Hypotrichida), each belonging to a complementary mating type, collected from the Somalian and the Tuscan coasts have been examined by electron microscope. Several morphologically distinguishable types of bacteria-like endosymbionts have been shown to live in the cytoplasm of E. crassus cells. Type A endosymbionts appear to be always present in the non-autogamous cells of E. crassus. Indeed, type A was found both in the Tuscan stocks, where it is the only one present, and in the Somalian stocks where it coexists with the more numerous type B endosymbionts. One of the two Somalian autogamous stocks contains type C, while the other has type D endosymbionts.