• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.4
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• pp.253-260
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• 2008

Gonadal development, gametogenesis, reproductive cycle, spawning, relative weight of flesh, and onset of sexual maturity of the murex shell, Ceratostoma rorifluum, collected from the rocky intertidal zone of Daehang-ri, Buan-gun, Jeollabuk-do, Korea were investigated monthly from January to December 2005 both cytologically and histologically. The gonads were widely placed on the digestive gland located in the posterior spiral fleshy part in the shell. C. rorifluum had separate sexes, and was an internal fertilizer. The sex ratio of females to males was approximately 1:1. The ovary and testis contained a great number of oogenic follicles and spermatogenic tubules, respectively. The oogonia and fully ripe oocytes were $15-19{\mu}m$ and $150-160{\mu}m$ in diameter, respectively, and the cytoplasm of the ripe oocytes contained a number of yolk granules. The relative weight of flesh reached a maximum in August($39.35{\pm}0.40%$), and then decreased rapidly in November($32.75{\pm}1.20%$). The percentages of female and male snails at first sexual maturity with shell heights ranging from 12.1-14.0 mm were 60.0% and 52.9%, respectively, while 100% of the snails of both sexes with shell heights over 18.1 mm were reproductively active. Based on the gonadal development and histological observations, the reproductive cycle of the snail could be categorized into five successive stages: early active(December to May), late active(March to July), ripe(June to September), spawning(July to October), and recovery(October to March). C. rorifluum spawned once a year between July and October, and the majority of spawning occurred in September when the seawater temperature exceeded $23.5^{\circ}C$.

• The Korean Journal of Malacology
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• v.28 no.4
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• pp.363-375
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• 2012

The gametogenic cycle, the number of spawning seasons per year and first sexual maturiity of the pen shell, Atrina (Servatrina) pectinata, were investigated by quantitative statistical analysis using an Image Analyzer System. Compared two previous results (the spawning periods in the reproductive cycles in 1998 and 2006) by qualitative histological analysis with the present results by quantitative statistical analysis, there are some differences in the spawning periods: the spawning period (June to September) by quantitative statistical analysis was one month longer than those of two previous reports (June to July or June to August) by qualitative histological analysis. However, the number of spawning seasons studied by the qualitative and quatitative analyses occurred once per year. In quantitative statistical analysis using an image analyzer system, the patterns of monthly changes in the percent (%) of the areas occupied by follicles to the ovary area in females (or that of the areas occupied by spermatogenic stages to the testis area in males) showed a maximum in May, and then sharply droped from June to September, 2006. From these data, it is apparent that the spawning season of A. (S.) pectinata occurred once a year from June to September, indicating a unimodal gametogenic cycle during the year. Shell heights of sexually mature pen shells (size at 50% of group sexual maturity, $GM_{50}$) that were fitted to an exponential equation were 15.81 cm in females and 15.72 cm in males (considered to be one year old).

• Korean Journal of Environmental Biology
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• v.32 no.2
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• pp.153-158
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• 2014

In order to determine the testicular cycle of the Korean brown frog, Rana coreana, the gonadosomatic index (GSI) and the changes of germ cells in testis for adult males were investigated throughout the year. The study indicated that the spermatogenesis in the seminiferous tubule of testis began in August and became most active in the month of September, and the GSI was recorded the highest and the cross area of seminiferous tubule was the widest on this period. Furthermore the seminiferous tubules at the post spawning stage appeared in testis during February, and the spermatogenesis was quiescence period of time from March to July and the GSI and the cross area of seminiferous tubule were found to be the lowest. Based on these observations, we suggest that, GSI of male Korean brown frog changes significantly between July to August, indicating the testicular cycle with discontinuous spermatogenic process, and the breeding season was confirmed to be February.

• Korean Journal of Environment and Ecology
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• v.29 no.4
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• pp.525-532
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• 2015

In order to determine the testicular cycle of the Asian toad, Bufo gargarizans, adult males of the species were captured around Jeongeup city (Jeollabuk-do, Korea) during March, 2012 to February, 2013 and the gonadosomatic index (GSI) and the changes of germ cells in their testes were investigated throughout the year. The study indicated that the spermatogenesis in the seminiferous tubule of testes began in April and became most active in July. The recorded GSI was the highest and the cross area of seminiferous tubule was the widest in this period. The seminiferous tubules at the post spawning stage appeared in February, the largest amounts occurred in March and primary spermatogonia also appeared in this period. The GSI and the cross area of seminiferous tubules were found to be the lowest in March, indicating a testicular cycle with potentially continuous spermatogenic process. According to the findings above, it is confirmed that testicular spermatogenesis takes place actively between April to July in male Asian toad and that their breeding season is February to March.

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.261-271
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• 2011

The gametogenic cycle, the spawning season and the biological minimum sizes in female and male Protothaca (Notochione) jedoensis were investigated by quantitative statistical analysis. In females, monthly changes in the percents of the follicle areas to the ovarian tissue areas and the percents of the oocyte areas to the ovarian tissue areas increased in February and reached the maximum in April, and then gradually decreased from May to July, with the spawning peak between June and July. In males, monthly changes in the percents of the testicular tissue areas to total tissue areas and the percents of the spermatogenic stage areas to the testicular tissue areas increased in February and reached the maximum in April, and then showed a rapid decrease from May to July. From these data, it is apparent that the number of spawning seasons in female and male P. (N.) jedoensis occurred once a year, from May to July. Therefore, P. (N.) jedoensis in both sexes showed a unimodal gametogenic cycle during the year. Compared the gametogenic cycle by quantitative statistical analysis in 2007 with the previous qualitative results of this species, the results of the gametogenic cycle calculated by quantitative statistical analysis showed some differentiations in the spawning seasons evaluated by the gonad index by qualitative histological analysis. The intervals of the beginning of two spawning seasons showed one month between the results of quantitative and qualitative analyses. The biological minimum sizes (considering to 50% of group sexual maturity) in female and male clams by quantitative analysis of this species are 32.01 mm in shell length in females and 30.58 mm in males, respectively. According to the mean shell length fitted to von Bertalanffy's equation, 30.58 and 32.01 mm in shell length were considered to be two years old. Therefore, we assume that both sexes of this population begin reproduction from two years of age.

• Toxicological Research
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• v.19 no.2
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• pp.83-90
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• 2003

Since histopathological examination was known to be the most sensitive evaluation for testicular toxicity, regulatory authorities have been published the guidelines on practical testicular assay approach. Those guidelines specified details of evaluation including fixation, embedding, stain-ing, histological examination and also seminiferous tubular staging methods. However, there have been confusing understanding among toxicologists and even pathologists on staging theory and its application on industrial testicular toxicity. Guidelines did not intend to conduct quantitative assay with staging but recommended the use of knowledge of staging. To count each tubular stage with statistical analysis is known to be time consuming and labor burdening work but the significance of toxicity has little value. It also has been pointed out that the application of staging theory for longer-term toxicity considered to be lacking of rationale. It could be recommended that qualitative assay with aware-ness of germ cell loss is more efficient method rather than quantitative counting of each tubular stage. Therefore it would be required that comprehensive understanding of testicular toxicity evaluation and the use of testicular staging method.

• Korean Journal of Environmental Biology
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• v.24 no.1 s.61
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• pp.1-6
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• 2006

Abstract - Global decline in wildlife mammals has been accelerated during past decades. Especially the conservation the wild life mammals in polar areas, is urgent. In an effort to understand the reproduction of the seals dwelling in the polar area, spermatogenesis in the seals was reviewed. Seals breed seasonally and in most of the seal species, delayed implantation is frequently observed. To date, histological and endocrinological evaluation revealed highly cyclic nature in supermatogenesis and steroidogenesis in testis. Seasonal changes in blood testosterone level together with melatonin is closely related with changes in light cycle between summer and winter. In adult testis at breeding seasons, spermatogenesis is manifested by consecutive 18 stages of germ cell development. Three kinds of Leydig cells different in steroidogenic activity as well as cellular morphology appear during the testis development. During non-breeding season, spermatogenic arrest and Leydig cell hypoplasia are frequently found. Interestingly, blood circulation through the anastomoses of pelvic veins cooled the testes and thus guarantees spermatogenesis within the body trunk. Endocrine disruptors and heavy metals have been found in the body tissues of several seals species and alter steroidogenesis in seals, suggesting environmental pollutants together with decrease in habitats are potentially threatening the reproductive success in seal species.

• Korean Journal of Veterinary Research
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• v.29 no.4
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• pp.417-424
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• 1989

This study was conducted in order to observe the changes in cellular association of seminiferous tubules from 4 to 22 weeks of age and to obtain the cycle and relative duration of seminiferous epithelia from 24 weeks of age in male ducks. Fifety-five male ducks were used in the experiment and divided into 11 groups, consisting of 5 male ducks each, with 2 weeks intervals from 4 to 24 weeks of age. The results were summarized as follows: 1. The body and testes weight showed most rapid increase during 4 to 6 weeks and 18 to 22 weeks of age, respectively. The seminiferous tubules were obruptly enlarged in diameter of tubules during 18 to 22 weeks of age. 2. Gonocytes were seen from 4 to 6 weeks of age, however they were not observed as from 8 weeks of age. Both type Ap spermatogonia and type Ad spermatogonia occured from 8 to 12 weeks of age, while spermatocytes and spermatids were beginning to appear at 16 weeks and 18 weeks of age, respectively. Spermatozoa were first observed at 20 weeks of age. Full spermatogenic activity was completed at the age of 20 weeks. 3. Average paired weight of the testes in male ducks was 78g at 24 weeks of age and its ratio to the body weight was approximately 2.5 percent. 4. Average diameter of seminiferous epithelium at 22 weeks of age was $232{\mu}m$, and average numbers of Sertoli cell, spermatogonia, spermatocyte, spermatids and spermatozoa in the cross section of seminiferous epithelium were 15.30, 59.08, 41.78, 71.11 and 165.30, respectively. Spermatogonia and spermatids were classified into 2 and 4 types, respectively. 5. The cycle of the seminiferous epithelium could be divided into 5 stages at 24 weeks of age. The relative frequencies of stages from I to V were 13.5%, 25.0%, 22.3%, 20.6% and 18.7% respectively. Thus, establishment of spermatogenesis in male ducks were beginning to appear at 20 weeks of age.

• Applied Microscopy
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• v.22 no.2
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• pp.97-117
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• 1992

In order to study process of spermiogenesis of the Korean greater horseshoe bat, Rhinolophus ferrumequinum korai, the cycle of seminiferous epithelium was examined by the light and electron microscope and the following results were obtained based on the epithelial cell differentiation. 1. Spermiogenesis occurred from early July to mid-Octber, and spermatogenic activity was vigorous from mid-August to late September. Spermatocytes including spermatogonia were found to be degenerated in only July. It is deduced that the degeneration serves as the mechanism to regulate effective use of energy to prepare for mating and hibernating periods, and regulation of breeding cycle. 2. Spermiogenesis of the Korean greater horseshoe bat was divided according to differentiation of the cell structure, into Golgi, cap, acrosome, maturation and spermiation phases; Golgi, cap and spermiation phases were further divided into two steps of early and late phase respectively, and acrosome phase into three steps of early, mid and late phases, and maturation phase has only one step. Hence, the spermiogenesis consists of ten phases. The first research was done in this article on the changes of chromatin with nucleus, the time of appearance and disappearance of chromatin granules, in case of Korean greater horseshoe bat (Rhinolophus ferrumequinum korai). Chromatin granule began to be condensed in late Golgi and the condensation proceeded to form an irregular mass of a electron-dense chromatin in a form of circular cylinder in the center of nucleus at the phase of maturation. Finally, the chromatin condensation proceeded and perfect nucleus of sperm with homogeneous density was formed when the sperm was separated from Sertoli cell. Therefore, appearance and disappearance of chromatin granules occurred in the period of time between late Golgi and maturation phase, The tail of sperm began to develop in early cap phase, Numerous lipid droplets were obseved in the cytoplasm of spermatids during the maturation phase, which seemed to be used as energy source necessary to make mature sperm during spermiogenesis.

• The Korean Journal of Malacology
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• v.27 no.1
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• pp.43-53
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• 2011

The gametogenic cycle and the spawning season in female and male Cyclina sinensis were investigated by quantitative statistical analysis using an image analyzer system, and the biological minimum size (the size at 50% of sexual maturity) was calculated by combination of quantitative data by size and von Bertalanffy's equation. Compared the gametogenic cycle by quantitative statistical analysis with the previous qualitative results in female and male C. sinensis, monthly changes in female and male gametogenic cycles calculated by quantitative statistical analysis showed similar patterns to the gonadal stages in female and male reproductive cycles by qualitative histological analysis. Comparisons of monthly changes in the portions (%) of each area to eight kinds of areas by quantitative statistical analysis in the gonads in female and male C. sinensis are as follows. Monthly changes in the portions (%) of the ovary areas to total tissue areas in females and also monthly changes in the portions of the testis areas to total tissue areas in males increased in March and reached the maximum in May, and then showed a rapid decrease from June to October. Monthly changes in the portions (%) of oocyte areas to ovarian tissue areas in females and also monthly changes in the portions of the areas of the spermatogenic stages to testis areas in males began to increase in March and reached the maximum in June in females and males, and then rapidly dropped from July to October in females and males when spawnig occurred. From these data, it is apparent that the number of spawning seasons in female and male C. sinensis occurred once per year, from July to October. Monthly changes in the number of the oocytes per mm2 and in the mean diameter of the oocyte in captured image which were calculated for each female slide showed a maximum in May and reached the minimum from December to February. Therefore, C. sinensis in both sexes showed a unimodal gametogenic cycle during the year. The percentage of sexual maturity of female and male clams ranging from 25.1 to 30.0 mm in length was over 50% and 100% for clams over 40.1 mm length. In this study, the biological minimum size (sexually mature shell lengths at 50% of sexual maturity) in females and males were 26.85 and 26.28 mm, respectively.