ULTRASTRUCTURE AND CYTOCHEMISTRY OF EARLY SPERMATANGIAL DEVELOPMENT IN ANTITHAMNION-NIPPONICUM (CERAMIACEAE, RHODOPHYTA)

Spermatial development and differentiation of wall components were inv estigated by electron microscopy and cytochemical methods in Antithamn ion nipponicum Yamada et Inagaki. The spermatium is composed of two pa rts, a globular head and two appendages projecting from near the basal portion. The appendages originate from spermatangial vesicles (SVs) a nd follow a developmental sequence beginning as amorphous material and ending as fully formed fibrous structures compressed within the Svs. SV formation is due to contributions initially from endoplasmic reticu lum and later from dictyosome-derived vesicles. Chemical differentiati on of the spermatial wall occurs early in its development. Calcofluor white ST does not label spermatial walls, indicating an absence of cel lulose polysaccharides, which are abundant in vegetative cell walls. L abeled lectins show that alpha-D-methyl mannose and/or alp[ha-D-glucos e as well as N-acetyl-glucosamine, beta-D-galactose, and alpha-L-fucos e moieties are present on the spermatial wall but not in the vegetativ e cell wall. The glycoconjugate with alpha-D-methyl mannose and/or glu cose residues, previously reported as a gamete recognition molecule in this species, is distributed along the surface of spermatia as well a s in the SV during spermatangial development.