Ultrastructure of carposporophyte development in the red algaCaulacanthus ustulatus (Gigartinales: Caulacanthaceae)

The ultrastructure of carposporophyte development is described for the red algaCaulacanthus ustulatus (Turner) Kützing collected at Epanomi (Gulf of Thessaloniki, Greece) and studied in 1988/1989. Following presumed fertilization the diploid nucleus is transferred to the auxiliary cell which expands and cuts off several multinucleate gonimoblast initials. The gonimoblast initials are distributed around the periphery of the cystocarpic cavity and divide further to produce generative gonimoblast cells. The latter cleave repeatedly to form clusters of carpospores. Thus, carposporophyte development proceeds inwardly. The first formed gonimoblast cell is transformed into a storage gonimoblast cell containing large quantities of starch granules and presumably functioning to supply nutrients. A fusion cell is never formed. Gonimoblast initials contain typical red algal proplastids and numerous sacs and/or vesicles originating from cytoplasmic concentric membranes.Please address all correspondence and requests for reprints to Dr S. G. Delivopoulos