• Applied Microscopy
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• v.40 no.4
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• pp.253-259
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• 2010

The ultrastructure of sperms in testes of the pond smelt (Hypomesus nipponensis) was investigated using electron microscopes. The whitish testis was located between swim bladder and intestine. Especially, the left testis was larger than the right testis. The sperm was approximately $26\;{\mu}m$ in length. The sperm had an oval head and the acrosome was not found. The nucleus was about 400 nm in diameter and chromatin was incompletely condensed. The nuclear fossa deeply formed in sperm head and two centrioles were located in the fossa. The mitochondrium was observed only one in midpiece of the sperm and a motile flagellum consisted of an axoneme with a typical 9+2 pattern of microtubule. Also, the tail of the sperm has axonemal fins.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.641-645
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• 2003

Spermatogenesis, ultrastructure, and sperm morphology of the Pacific oyster (Crassostrea gigas) were investigated with TEM and SEM. C. gigas sperm were primitive consisting of a head midpiece and tail. Sperm size (head and midpiece) was about 1.78 ${\mu}m$. Sperm morphology was similar to a sharp of a small water jar with a rough surface. Sperm had both anterior nuclear fossa (anf) and posterior nuclear fossa (pnf). Acrosome forms had a hat-like shape. The axial rod was projected in front of the acrosome. C. gigas sperm had four large mitochondria in the midpiece.

• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.5
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• pp.504-511
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• 2002

Ultrastructure and sperm morphology were investigated Mactra venerifomis, Mactra chinensis, Spisula sacharinensis, Tresus keenae in Mactridae. All the sperm studied were primitive type. They consisted of three parts; the head, the middle piece and the tail part. The acrosome forms were similar among the 4 species. The acrosome was shaped like a modified hat. It was consisted of two different parts in electronic density; the anterior part, electric lucent part (elp), and the posterior part, electric dense part (edp). But nuclei forms were slightly different among the species. All the species studied had 4 mitocondria at middle piece. We guessed that the Mactridae sperm were family-specific with characterful acrosome shape.

• Korean Journal of Animal Reproduction
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• v.26 no.4
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• pp.353-360
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• 2002

Although successful pronuclear formation and apposition were seen in porcine oocytes following mouse sperm injection, little is known on the morphology of male and female pronuclei following sperm injection. The objective of this study is to describe the ultrastructure of porcine zygote following murine sperm injection in relation to the chronology of pronuclear S phase. At 40h ~ 44h following in vitro maturation, Cumulus cells were removed in TCM-HEPES with 0.1% hyaluronidase. Then, spermatozoa was injected into the cytoplasm of oocytes. After. injection, all oocytes were transferred to NCSU23 medium and cultured at 39$^{\circ}C$ under 5% $CO_2$ in air. Oocytes were fixed in 2% glutaraldehyde in Dulbeccos phosphate-buffered saline and observed by Transmission Electron Microscopy. Nuclear precursor bodies were observed in each pronucleus. A cluster of large and small granules was attached in the nucleolus precursor body. After the apposition of male and female chromatin, chromatin condensation was observed throughout the nucleoplasm and nucleolus precursor bodies and condensed chromatin in contact with clusters of small and large granules and the nuclear envelope were found in apposed pronuclear regions. These results suggest that non-species specific nuclear cytoplasmic interactions take place during pronuclear formation and apposition following sperm injection.

• Applied Microscopy
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• v.35 no.4
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• pp.32-41
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• 2005

The sperm morphology of two Korean frogs, Rana catesbeiana and R. nigromaculata (Ranidae) was studied with the light microscope, scanning and transmission electron microscopes. Sperm heads of the R. catesbeiana and R. nigromaculata were long-cylinder shapes. In the total length of R. nigromaculata sperm ($51.2{\mu}m$) was longer than those of R. catesbeiana ($44.6{\mu}m$). Both R. catesbeiana and R. nigromaculata had the long head and principal piece, and short middle piece, but the neck was undeveloped. The axonemal structures contain a 9+9+2 arrangement of microtubules. The number of mitochondria in middle piece have less than mammalian sperm, which irregular surrounded the axone of the middle piece. In conclusion, R. catesbeiana and R. nigromaculata shared many similar features in sperm heads, neck, middle piece, and a site of mitochondria and axial structure, and it suggests that these species should be closely related.

• Fisheries and Aquatic Sciences
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• v.10 no.3
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• pp.143-149
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• 2007

This study describes spermatogenesis and sperm ultrastructure of the granular ark, Tegillarca granosa using light and electron microscopy. In the active spermatogenic season, the testis comprises many spermatogenic follicles that contain germ cells in different developmental stages. Primary spermatocytes in the pachytene stage are characterized by synaptonemal complexes. The early spermatids are characterized by the appearance of several Golgi bodies, increased karyoplasmic electron density, and tubular mitochondria. The mass of proacrosomal granules consists of numerous heterogeneous granules with high electron density that are about 20 nm in diameter. From the midstage of spermiogenesis, the well-developed mitochondria in the cytoplasm aggregate posterior to the nucleus and surround the proximal and distal centrioles. The proacrosomal granules condense and form a single acrosome with a thin envelope. During late spermiogenesis, the acrosome begins to elongate becoming conical. The sperm is approximately $35.0{\mu}m$ long and consists of a head, midpiece, and tail. The head comprises a round nucleus and a conical acrosome. A micro fibrous axial rod is observed between the nucleus and acrosome. The midpiece has a calyx-like structure with five mitochondria, and the tail, which has the typical "9+2" microtubular system, originates from the distal centriole.

• Applied Microscopy
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• v.32 no.4
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• pp.303-310
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• 2002

Spermatogenesis and sperm ultrastructure are investigated by means of light and transmission electron microscopy in the equilateral venus, Gomphina veneriformis which is dominant bivalve in the east coast of Korea. In the active spermatogenic season, testis consists of numerous spermatogenic follicles which is contains germ cells in the different developmental stage. The spermatogonia attached to spermatogenic follicle wall and has a large nucleus with electron-dense nucleolus. The spermatocytes are characterized by appearance of synaptonemal complex and well-developed Golgi complex. Nucleus of spermatid consists of numerous heterogeneous granules with high electron density. Karyoplasmic condensation, acrosome and flagellum formations are observed during spermiogenesis. Testicular matured sperms of sperm bundle consists of head, midpiece and tail. The head is about $8.5{\mu}m$ long and comprises a long nucleus and a bullet-like acrosome ($8.5{\mu}m$ in length). Acrosomal rod of microfilaments is observed in the lumen between nucleus and acrosome. The midpiece has four mitochondria. And tail has the typical '9+2' microtubule system.

• 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.