The ultrastructure of nuclear division inThraustochytrium sp.

Abstract

The first morphologically detectable event signaling the onset of mitosis inThraustochytrium is the duplication of the Golgi body, followed by duplication of the centrioles. The Golgi bodies and centrioles migrate to a position associated with the poles. The nuclear envelope, except for polar fenestrae, remains intact at metaphase. Gaps in the nuclear envelope at the interzonal region develop at anaphase. Separation of chromatic material is accomplished initially by reduction in chromosome to pole distance followed by elongation of the nucleus (pole to pole distance). The cellular material found in the interzonal region is largely excluded at the time of daughter nuclei formation.