Developmental Cytology of Dictyosphaeria cavernosa. I. Light and Electron Microscope Observations on Cytoplasmic Cleavage in Zooid Formation

Abstract

Zooid formation in D. cavernosa (Forssk.) Borg. was followed with the light microscopy and EM. Cytoplasmic partitioning is first facilitated by aggregation of the cytoplasm, resulting into a network. This network cytoplasm is invaginated by the ramifying intrusion of cleavage furrows, the membranes of which are partially Golgi derived. During this stage centrioles previously situated at the nuclear poles were converted to flagellar basal bodies. Roots of each basal body complex appear to play an important role in compartmentalization of individual swarmers. Neither a phycoplast nor a phragmoplast was involved in the cytoplasmic cleavage. Instead, electron dense granules accumulated along the cleavage plane. Abnormal zooid formation is briefly discussed.