The Ultrastructure of Grateloupia filicina (Halymeniaceae, Rhodophyta) Pit Plugs

Abstract

Cultured Grateloupia filicina was used as the material for observations on spore development and the ultrastructure of pit plugs. The general characteristics of the pit plugs were the same in the discs, filaments and frond-like thalli of this red alga. The pit plugs were naked (no cap layers) with a cap membrane and a plug core. The matrix was diffuse in the center and dense in the outer portion. However, the sizes and shapes of the pit plugs varied. Pit plugs of the filament-like medullary cells of the frond-like thalli were the largest. These pit plugs were H-shaped with a deep central constriction. Pit plugs of the filament cells, were bead-shaped and were smaller than those of the medullary ones. In contrast, pit plugs of the cortex of the frond-like thalli were the smallest. The pit plugs of disc cells and terminal ball-like structures on filaments, were a little larger than the cortex and filament cell pit plugs, and were roughly round-shaped, like those of the cortex. This study confirms that the pit plugs of red algal vegetative cells have taxonomic value, even among the same species in different growth phases.