COMPARATIVE FINE-STRUCTURAL INVESTIGATIONS OF INTERPHASE AND MITOTIC NUCLEI OF VAMPYRELLID FILOSE AMEBAS

The nuclei of trophozoites and digestive cysts as well as mitotic nucl ei of several species of the vampyrellids Vampyrella, Gobiella, Hyalod iscus, Arachnula, and Leptophrys were investigated by electron microsc opy. Except for some species of the genus Hyalodiscus, the vampyrellid s are generally multinucleate. The nuclei of the trophozoite stage are in interphase. These nuclei are spherical, except for the genus Arach nula, which reveals elongated nuclei. In digestive cysts of all vampyr ellids the nuclei enlarge and the pars granulosa of the nucleoli becom es prominent. Karyokineses take place synchronously in older digestive cysts, which transform into reproductive cysts. The nuclei divide by closed intranuclear orthomitosis. In telophase the old nuclear envelop e disintegrates and a new one is rearranged. Only in the genus Leptoph rys the nuclear envelope decomposes before telophase. Neither centriol es nor MTOC-plaques have been found in any stage of mitosis. After kar yokinesis the cell divides inside the cyst or when leaving the cyst.