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The gametes of chlorophytes can be divided into two morphological types (types α and β) based on the position of the mating structure relative to the flagella and eyespot. To elucidate the relationship between the morphological types and the sexes, we studied spatial relationships between the flagellar apparatus‐eyespot‐mating structures in biflagellate male and female gametes and their fate after fertilization in the anisogamous (Monostroma angicava) and the slightly anisogamous species (Collinsiella cava) using field emission scanning electron microscopy and transmission electron microscopy. The smaller male and larger female gametes of M. angicava had two basal bodies arranged at a 180° angle and the cell surface coated with square‐shaped body scales, except for the flagella and mating structures. The mating structure of the female gamete was located on the same side of the flagellar beat plane as the eyespot (type β), whereas that of the male gamete was located on the opposite side (type α). This mating structure arrangement was also confirmed in C. cava. The initial fusion when male and female gametes were mixed involved the mating structures. In a fusing pair of gametes, each flagellum of one gamete lay alongside one flagellum of the other gamete. As fusion proceeded, the gamete pair transformed into a quadriflagellate planozygote, in which the four basal bodies were arranged in a cruciate pattern. The eyespots were positioned side‐by‐side on the same side of the cell. These results suggest that the two morphological types of gametes are intimately correlated with the particular sexes. [ABSTRACT FROM AUTHOR]

Cell surfaces of biflagellate gametes and their morphological changes during fertilization ofBryopsis maximaOkamura 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 ofB. maximahave sex-specific surface structures that change their morphology during fertilization and settlement. [ABSTRACT FROM AUTHOR]

Although may ultrastructural morphological studies have been undertaken on the lingual papillae of the rabbit tongue, relatively few have dealt with the microvascular structure and classification of the foliate papillae (FoP) in microvascular cast specimens (MVCS) by means of scanning electron microscopy (SEM). For the present study, a three-dimensional observation and classification was carried out by SEM. The morphological characteristics of the outer frame structure composed of the ascending and descending capillary branches, were observed by means of MVCS of FoPs which were located on both posteroperipheral parts of the tongue. They showed a bead-like appearance and consisted of 14∼18 even, transverse and slightly bent fin-like structures, running from the dorsal surface to both peripheral sides symmetrically. FoPs could be classified into two types: typical or manely symmetrical and atypical or manely asymmetrical. The typical type was subdivided into three types: type I was symmetrically made up of 14 fins, type II of 16 fins, type III of 18 fins. The atypical type was subdivided into two subtypes: type IV was asymmetrically made up of 14 fins (left side) and 16 fins (right side), type V of 18 fins (left side) and 16 fins (right side). Half of the 65 cases were type II (50.8%), consisting of 16 fin-like microvascular structures, and there were no sex and age differences found. These are fin-like microvascular structures seen to increas on the surface areas and to play a functional role in sensing taste. [ABSTRACT FROM AUTHOR]