ULTRASTRUCTURE OF THE GAMONT SHELL AND NUCLEUS IN THE POLYTHALAMOUS FORAMINIFER ELPHIDIUM-PONTICUM

The nucleus and shell structure of the growing and mature uninucleate gamonts of the polythalamous foraminifer Elphidium ponticum were studi ed using the material collected at the Karadag Biological Station (Bla ck sea). The mature gamont has 12-14 chambers and a single voluminous nucleus measuring up to 70 mu m in diameter. It usually lies in the ei ghth to tenth chamber. The outline of the nucleus of the growing gamon t is smooth, it stains light in semithin sections; the nucleus of the adult gamont is slightly smaller and stains dark, its outlines being l obulated. The chromatin is fully decondensed inside the nucleus and in visible in ultrathin sections. Multiple nucleoli are mainly peripheral . They are more numerous, larger and denser in the grown gamont. The n ucleoli are mainly dense fibrillar and contain fibrillar centres. They are linked to the nuclear envelope by fibrogranular aggregates, possi bly chromatin. This connection is more clear in the growing gamont tha n in the adult one. A study of the texture of the shell by scanning el ectron microscopy allowed to observe some new features of its structur e and to identify the variability of the shell structure of specimens from the same locality.