Browsing by Author "G. Kaneko"

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    Oocyte Differentiation and Reproductive Health of Solitary Tunicate (Styela plicata) from Eastern Coast of Thailand
    (2021-01-01) S. Senarat; J. Kettratad; P. Boonyoung; W. Jiraungkoorskul; F. Kato; E. Mongkolchaichana; G. Kaneko; P. Poolprasert; Navamindradhiraj University; University of Houston-Victoria; Rajamangala University of Technology Srivijaya; Pibulsongkram Rajabhat University; Chulalongkorn University; Mahidol University; Kyushu University; Prince of Songkla University
    Histopathological examination is a widely acknowledged technique to assess the reproductive health of aquatic organisms, but it has never been applied to the tunicate Styela plicata, a potential indicator species of water quality. In this study, we examined the oocyte differentiation of S. plicata obtained from the eastern coast of the Gulf of Thailand in order to provide basic information for future assessment of its reproductive health. The mature gonad of S. plicata comprised several ovo-testicular convoluted tubes, in which each tube was divided into apical and terminal portions. The ovarian tissue is located in the apical part of the tunicate body and contained oocytes of various differentiation stages (asynchronous development type) consisting of the four phases namely oogonial proliferation phase, primary growth phase, secondary growth phase (secondary growth and full-growth stages), and post-ovulatory phase. Changes in the morphology of oocytes and follicular cells were described for each differentiation stage. In addition, we unexpectedly observed a high prevalence of atretic follicles (24.5%), which might indicate the oocyte damage by environmental stresses. These findings would be useful for future assessment of reproductive histology of S. plicata and other tunicate species from environmental perspectives.
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    Spermatogenic Ultrastructure of the Grunting Toadfish Allenbatrachus grunniens (Batrachoididae)
    (2021-05-01) N. Sukkhee; T. Mitparian; T. Kanjanarakha; S. Senarat; W. Jiraungkoorskul; N. Kangwanrangsan; G. Kaneko; J. Kettratad; University of Houston-Victoria; Rajamangala University of Technology Srivijaya; Chulalongkorn University; Mahidol University
    Abstract: In the present study, we describe the spermatogenesis of Allenbatrachus grunniens, a benthic toadfish from Estuarine Pranburi River, Thailand, at the ultrastructural level. According to the nuclear and cytoplasmic characteristics, A. grunniens spermatogenic cells are classified into five stages. The spermatogonium contains the prominent nucleus and locates in the periphery of the seminiferous lobule. The spermatogonium develops into the primary spermatocyte and then into secondary spermatocyte, which was characterized by the dramatical increase in heterochromatin. The subsequent spermatids exhibit the centriole formation, chromatin condensation, mitochondrial redistribution, and reduced cytoplasm. After the final morphological differentiation, the spermatozoon shows an oval head with a high degree of chromatin condensation, a small midpiece consisted of prominent basal bodies surrounded by eleven mitochondria, and the biflagellate tail. Our observation demonstrates the ultrastructure of Batrachoididae spermatozoa, which can help to understand their reproductive biology.