The ultrastructure of reproduction in the brown algaPylaiella littoralis

Abstract

The ultrastructure of the later stages of gametogenesis in plurilocular gametangia ofPylaiella littoralis is described. Following a series of cell divisions, a large number of cells are present in the gametangium, each one delineated by a cell wall, and all enclosed within original vegetative cell walls. Paramural bodies are common during the division stages. Flagellum and mastigoneme formation, which occur after the period of cell division, are the major ultrastructural events in later stages of gametogenesis. Developing mastigonemes were observed in the perinuclear continuum and in ER cisternae. Mastigonemes were not observed in Golgi cisternae, although it is believed that they do occur there and that this stage was not observed. Flagella are formed in vesicles in the cytoplasm. The later stages of gametogenesis in plurilocular gametangia are compared to similar stages in plurilocular reproductive structures from diploid plants, which indicates an essentially similar pattern of development for both. A comparison is made between flagellum and mastigoneme formation in plurilocular gametangia ofPylaiella littoralis and in unilocular sporangia of the same species, which indicates that the processes are similar in both. A general pathway for development of mastigonemes inPylaiella is also suggested.