SEX‐SPECIFIC CELL SURFACE STRUCTURE OF ANISOGAMETES: MORPHOLOGICAL CHANGES DURING FERTILIZATION OF BRYOPSIS MAXIMA (ULVOPHYCEAE, CHLOROPHYTA) REVEALED BY ULTRA–HIGH‐RESOLUTION FIELD EMISSION SEM¹

Abstract

Cell surfaces of biflagellate gametes and their morphological changes during fertilization of Bryopsis maxima Okamura were observed using a high-resolution field emission scanning electron microscope. Male gametes have broad and narrow faces, which are divided into at least five morphologically distinct regions: 1) the apical plate is a plate-like structure that is approximately 380-530 nm long and approximately 190 nm wide, in the center of the papilla and slightly protruded from the plasma membrane; 2) strips are smooth materials on ridges that originate from the basal part of the papilla and extend downward; 3) the lateral belt is a belt-shaped structure on the center of the narrower faces; 4) the flagellar surface; and 5) the other region of the cell body has a fine-grained appearance. In contrast, the entire female gamete surface is rough because of many granular or amorphous cell coats on the plasma membrane. When both gametes were mixed together, the initial fusion proceeded between the broader face of the male gamete and the anterior side of the female one near the basal bodies. Morphology of the male gamete's cell surface changed gradually as fusion proceeded and was covered by the granular materials; that surface closely resembled those of female gametes except for the apical plate. It was present until the planozygote attached itself to the substrate by the papilla. It finally disappeared after settlement. Therefore, these results indicate that gametes of B. maxima have sex-specific surface structures that change their morphology during fertilization and settlement.

Inheritance pattern of chloroplast DNA is correlated with gamete types based on sex‐specific arrangement of the cell fusion site in Caulerpa (Ulvophyceae, Chlorophyta)

“…1A,B). Furthermore, in cases where only the female gamete has an eyespot, such as those of anisogametes of caulerpalean algae Bryopsis maxima Okamura (Hori 1988; Miyamura et al . 2005) and Caulerpa racemosa var.…”

Cytoplasmic inheritance in green algae: patterns, mechanisms and relation to sex type

“…in C. reinhardtii and G. pectorale, while they were inherited from female gametes (MID-) in V. carteri (Table 3). Table 3 Relationship between the transmission patterns of organelle genomes and the sex-specific features in green plants indicates the results of MGEC2 9 MGEC5 d 1, Sager (1954); 2, Boynton et al (1987); 3, Holmes and Dutcher (1989); 4, Ferris and Goodenough (1994); 5, Mori et al (2006); 6, Liu et al (2008);7, Hamaji et al (2008); 8, Adams et al (1990); 9, Miyamura (2003); 10, Kagami et al (2008); 11, Mogi et al (2008); 12, Kawano (2008); 13, Kuroiwa et al (1991); 14, Miyamura et al (2005); 15, Miyamura and Nagumo (2007); 16, Miyamura and Hori (1997); 17, Mori et al (2006); 18, Miyamura et al (1987); 19, Kirk and Tilney-Bassett (1978) Hamaji et al (2008) suggested that the patterns of mitochondrial inheritance changed at some point during the evolution of colonial Volvocales from uniparentally from the MID-containing parent (MID?) to uniparentally from the female (MID-).…”

Behavior of flagella and flagellar root systems in the planozygotes and settled zygotes of the green alga Bryopsis maxima Okamura (Ulvophyceae, Chlorophyta) with reference to spatial arrangement of eyespot and cell fusion site

“…The present study is intended to clarify such aspects of planozygote behavior using a siphonous green alga, B. maxima . Figure 1 portrays a schematic drawing of the biflagellate gametes and quadriflagellate planozygote representing the spatial relationship between the male and female flagella based on their ultrastructure (Hori 1988; Miyamura et al . 2005).…”

“… Schematic diagram of the mating male and female gametes and planozygote of Bryopsis maxima based on observations of previous (Hori 1988; Miyamura et al . 2005) and present studies.…”