An investigation of cystocarp development in Gelidium pteridifolium with a revised description of the Gelidiales (Rhodophyta)

Abstract

The Gelidiales possess a unique combination of characters that set them apart from all other orders of red algae. Our observations have revealed features in the development of the female reproductive system that differ from reports of previous workers. We find that in Gelidium pteridifolium nutritive filaments are initiated prior to carpogonial elongation; functional carpogonia are intercalary; a fertilized carpogonium becomes multinucleate as it cuts off gonimoblast initials; nuclei in the cortical filaments borne on the carpogonium divide and enlarge following fertilization and pit plugs break down forming channels between the carpogonium and adjoining cortical filaments; terminal gonimoblast cells first fuse with the terminal cells of nutritive filaments and later unite with the fusion cells themselves; unfused, uninucleate gonimoblast cells cut off the first carposporangia, and multinucleate fusion cells produce a second series of carposporangia later on. The auxiliary cell concept is reviewed as it has been applied to Gelidiales. We have provided a revised description of the order Gelidiales and discuss its status and possible taxonomic affinities.