• The Korean Journal of Malacology
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• v.26 no.4
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• pp.311-316
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• 2010

Spermatid differentiations during spermiogenesis and mature sperm ultrastructure in male Crassostrea nipponica were investigated by transmission electron microscope observations. The morphology of the spermatozoon of this species has a primitive type and is similar to those of other bivalves. Mature spermatozoa consist of broad, cap-shaped acrosomal vesicle and an axial rod in subacrosomal materials on an oval nucleus showing deeply invaginated anteriorly, two triplet substructure centrioles surrounded by four spherical mitochondria, and satelite fibres, which appear near the distal centriole. The acrosomal vesicle of spermatozoa of C. nipponica resemble to those of other investigated ostreids. Especially, two transverse bands (stripes) appear at the anterior region of the acrosomal vesicle, unlikely 2-3 transverse bands (stripes) in C. gigas. It is assumed that differences in this acrosomal substructure are associated with the inability of fertilization between the genus Crassostrea and other genus species in Ostreidae. Therefore, we can use sperm morphology in the resolution of taxonomic relationships within the Ostreidea. The sperm is approximately $48-50{\mu}m$ in length including an oval sperm nucleus (about $1.0{\mu}m$ in length and $1.41{\mu}m$ in width), an acrosome (about $0.48{\mu}m$ in length and 0.30 in width) and tail flagellum ($46-48{\mu}m$). The axoneme of the sperm tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail shows a 9 + 2 structure. These morphological charateristics of acrosomal vesicle belong to the family Ostreidae in the subclass Pteriomorphia.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.4
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• pp.281-286
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• 2004

Spermatogenesis and sperm ultrastructure of the marsh clam (Corbicula japonica) were investigated by electron microscopic observations. Testis of the marsh clam consists of numerous spermatogenic follicle containing germ cells in the different developmental stages. Spermatogonia are located nearest the outer wall of the follicle, while spermtocytes and spermatids are positioned nearer to the lumen. Spematogonia are oval-shaped and about $5{\mu}m$ In diameter. Spermatogonia develop into spermatocyte, spermatid and spermatozoon. In the spermatid to about $2{\mu}m$ in diameter, cytoplasm decreases and mitochondria move to the base of the nucleus and fuse into several spheres, the centrioles become orthogonally oriented, a flagellum appears, and an acrosomal vesicle forms. The mature sperm has primitive type, consisting of a head, a midpiece and a tail. The sperm was arrow-shaped, and its head is about $8{\mu}m$ long and comprised of a long nucleus and an acrosome. The four mitochondria encircled the centrosome in midpiece. The flagellum had the classical 9+2 axoneme structure, and axonemal lateral fins in the tail were observed.

• The Korean Journal of Malacology
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• v.28 no.1
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• pp.55-64
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• 2012

Ultrastructural studies of germ cell development during spermatogenesis and taxonomic values in mature sperm morphology of Argopecten irradians irradians were investigated by transmission electron microscopic observations. In the early stage of spermatid during spermiogenesis, a few granules and proacrosomal granules are formed by the Golgi complex. In the late stage of spermatid during spermiogenesis, a proacrosomal vesicle becomes an acrosomal vesicle in the acrosome through spermiogenesis. The sperm is approximately $ 45-48{\mu}m$ in length including a jar-shaped sperm nucleus (about $1.45{\mu}m$ long), an acrosome (about $0.34{\mu}m$ long) and tail flagellum. The axoneme of the sperm tail shows a 9+2 structure. As one of common characteristics of mature sperm morphologies in Pectinidae species in subclass Pteriomorphia, mature spermatozoon consists of the cone-shaped acrosomal vesicle and subacrosomal material on the invaginated jar-shaped nucleus. The acrosomal vesicle of this species is composed of electron high dense opaque part (material) from the base to the tip, as have seen in the species in the subclass Pteriomorphia. Exceptionally, five mitochondria are found in the sperm midpiece of this species, unlike four in most species of Pectinidae in subclass Pteriomorphia. However, the acrosomal vesicle of spermatozoa of A. irradians irradians resemble to those of other investigated Pectinidae species in subclass Pteriomorphia. Therefore, we can use sperm morphology as a tool in the resolution of taxonomic relationships within the Pectinidae species. These morphological charateristics of acrosomal vesicle belong to the family Pectinidae in the subclass Pteriomorphia.

• Development and Reproduction
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• v.17 no.2
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• pp.121-132
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• 2013

Ultrastructural characteristics of the germ cells and accessory cells in testis during spermatogenesis and taxonomic values of mature sperm morphology of Ruditapes philippinarum were investigated by the transmission electron microscope and scanning electron microscope observations. The testis is the diffuse organ that consists of branching acini containing developing germ cells and accessory cells associated with spermatogenesis. The morphology of the spermatozoon is of the primitive type and is somewhat different to those of other bivalves. The morphologies of the sperm nucleus type and the acrosome shape of this species have a cylinderical type and a modified cone shape, respectively. As some ultrastructural characteristics of the acrosomal vesicle, the peripheral parts of two basal rings show electron opaque part, while the apex part of the acrosome shows electron lucent part. These characteristics of sperm belong to the family Veneridae in the subclass Heterodonta, unlike a characteristic of the subclass Pteriomorphia showing all part of the acrosome being composed of electron opaque part. In particular, a cylinder-like nucleus of the sperm is curved. The spermatozoon is approximately $48-51{\mu}m$ in length, including a long acrosome (about $2.4{\mu}m$ in length), a curved sperm nucleus (about $3.40{\mu}m$ in length), and a tail flagellum. The axoneme of the sperm tail shows a 9+2 structure.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.3
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• pp.171-175
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• 2000

The ultrastructures of germinal cells of male marsh clam, Corbicujar lena were studied. The mature sperm was primitive type, consisting of head, middle piece and tail. The mature sperm was whip-shaped and its head was divided into two parts; the acrosomal part shaped long hollow cone about $3{\mu}m$ in length and the sperm nuclear part shaped a long stick about $9\;{\mu}m$ in length. The posterior part of the sperm nuclear projected to centriole, The middle piece of the sperm-nuclear had four mitochondria and two centrioles. The sperm tail part had the 9+2 microtubular arrangement known as a typical pattern, During spermiogenesis, chromatin within sperm nuclear became fiberic materials by condensation.

• The Korean Journal of Malacology
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• v.27 no.1
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• pp.55-65
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• 2011

Some characteristics of germ cell differntiations during spermiogenesis and mature sperm ultrastructure in male Phacosoma japonicus were investigated by transmission electron microscope observations. The morphology of the spermatozoon of this species has a primitive type and is similar to those of other species in the subclass Heterodonta. Morphologies of the sperm nucleus and the acrosome of this species are the cylindrical type and cap shape, respectively. The spermatozoon is approximately 45-50 ${\mu}m$ in length, including a long curved sperm nucleus (about $3.70{\mu}m$ long with 45 $^{\circ}$ of the angle of the nucleus, an acrosome (about $0.55{\mu}m$ in length), and tail flagellum (about 42-$47{\mu}m$)The axoneme of the sperm tail shows a 9+2 structure. As some characteristics of the acrosomal vesicle structures, the basal and lateral parts of basal rings show electron opaque part (region), while the anterior apex part of the acrosomal vesicle shows electron lucent part (region). These characteristics of the acrosomal vesicle were found in the family Veneridae and other several families in the subclass Heterodonta. These common characteristics of the acrosomal vesicle in the subclass Heterodonta can be used for phylogenetic and systematic analysis as a taxonomic key or a significant tool. The number of mitochondria in the sperm midpiece of this species are four, as one of common characteristics appear in most species in the family Veneridae and other families in the subclass Heterodonta. However, exceptionally, only three species in Veneridae of the subclass Heterodonta contain 5 mitochondria. The number of mitochondria in the sperm midpiece can be used for the taxonomic analysis of the family or superfamily levels as a systematic key or tools.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.2
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• pp.157-162
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• 2003

Ultrastructure of germ cell during gametogenesis of surf clam, Spisula sachalinensis were investigated by electron microscopic observations. Oogonia are oval in shape and 5-6 ${\mu}m$ in diameter. They contain a large nucleus and have several mitochondria in the cytoplasm. Vitellogenic oocytes grew attached by a stalk to the germinal epithelium in the ovarian sac and their cytoplasm contained many yolk granules, lipid granules and mitochondria. Mature oocytes measuring 50-60 ${\mu}m$ in diameter have a nucleus containing an electron dense nucleolus, and a lots of yolk granules, lipid granules, mitochondria, rough endoplasmic reticulum and cortical granules were present in the cytoplasm. The surface of the plasma membrane in mature oocytes was formed of microvilli approximately 1.5 ${\mu}m$ long and enveloped in the vitelline layer. Spematogonia are oval in shape and about 5 ${\mu}m$ in diameter. Sprmatogonia develop into spermatocyte, spermatid and spermatozoon. The spermatozoon consisted of the head, midpiece and tail. The sperm head with diameter of about 1.5 ${\mu}m$ was ovoid, and contained the nucleus which consisted of acrosome. The four mitochondria encircled the centrosome in midpiece. The flagellum measuring about 40 ${\mu}m$ long had the classical 9+2 axoneme structure.

• Development and Reproduction
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• v.18 no.3
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• pp.179-186
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• 2014

Characteristics of the developmental stages of spermatids during spermiogenesis and phylogenetic classicfication of the species using sperm ultrastructures in male Crassostrea ariakensis were investigated by transmission electron microscope observations. The morphology of the spermatozoon of this species has a primitive type and is similar to those of Ostreidae. Ultrastructures of mature sperms are composed of broad, modified cap-shaped acrosomal vesicle and an axial rod in subacrosomal materials on an oval nucleus, four spherical mitochondria in the sperm midpiece, and satellite fibres which appear near the distal centriole. The axoneme of the sperm tail shows a 9+2 structure. Accordingly, the ultrastructural characteristics of mature sperm of C. ariakensis resemble to those of other investigated ostreids in Ostreidae in the subclass Pteriomorphia. In this study, particularly, two transverse bands (stripes) appear at the anterior region of the acrosomal vesicle of this species, unlike two or three transverse bands (stripes) in C. gigas. It is assumed that differences in this acrosomal substructure are associated with the inability of fertilization between the genus Crassostrea and other genus species in Ostreidae. Therefore, we can use sperm ultrastructures and morphologies in the resolution of taxonomic relationships within the Ostreidae in the subclass Pteriomorphia. These spermatozoa, which contain several ultrastructures such as acrosomal vesicle, an axial rod in the sperm head part and four mitochondria and satellite fibres in the sperm midpiece, belong to the family Ostreidae in the subclass Pteriomorphia.

• Applied Microscopy
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• v.44 no.1
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• pp.1-7
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• 2014

The spermatogenesis of Siamese fighting fish, Betta splendens, belongs to Osphronemidae was investigated by light and electron microscopic observations. In primary spermatocyte stage, the nucleus was comparatively large ellipsoidal, and mitochondria showed a marked development in cytoplasm. In secondary spermatocyte stage, the germ cells were smaller than that of primary spermatocytes. The nucleus was a spherical shape and intercellular space was formed between germ cells. In spermatid stage, the early spermatids were not much different from a secondary spermatocyte. But, the chromatin condensation was occurred from the outside to the inside. The nucleus was more condensed. Intracellular space was larger than early spermatid. The mitochondria were rearranged in a middle piece, and occupied about half of the head part in early sperm. In sperm stage, the head of mature sperm was a spherical shape and had no acrosome. The flagellum was showed the typical 9+2 array of microtubules. Also, the tail of sperm had no lateral fins and outer coarse fibers. These ultrastructural characteristics can be used in classification of species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.2
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• pp.94-99
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• 2005

The gametogenesis of the surf clam, Tresus keenae, were investigated by SEM and TEM. Both the testis and the ovary had follicle tubes surrounded by inter-tubal tissue composed of adipogranular cells that provided storage function. In the vitellogenic oocyte, lipid droplets and lipid yolk granules were found in the vacuoles formed by the Golgi apparatus. Proteid yolk granules were formed by the endoplasmic reticulum and cortical granules in the cytoplasm during vitellogenesis. The mature sperm was primitive and resembled a jar with a cover. The sperm heads were approximately $2.00-2.30 {\cal}um$. The acrosomal rod projected in front of the acrosome. In addition, four large mitochondria were in the midpiece.