Jae Won Kim’s research while affiliated with Gangwon Provincial University and other places

This study was performed to obtain information on the sex ratio, spawning period, and size at sexual maturity for fishery management of the largehead hairtail Trichiurus japonicus in Korean waters. The overall sex ratio (female, F; male, M) was 1:0.46 (n = 1274 females:589 males, 68.4% female) and as fish increased in length, the proportion of females increased. The oocyte development pattern was group-synchronous development, for which oocyte groups at different stages can be identified within the same ovary. The average gonadosomatic index (GSI) showed two peaks in June (3.03) and August (3.10) in females and in May (1.81) and September (2.24) in males. The median value of GSI showed two peaks in May (2.65F, 1.78M) and September (2.55F, 1.87M) for both females and males. As a result of analyzing the GSI and the monthly gonadal developmental stages, the main spawning season was estimated to be bi-annual (May–June and September–October). The anal length of fish at 50% sexual maturity was analyzed using a logistic regression model and was determined to be 16.38 cm (female) and 18.31 cm (male).

This study was performed to obtain information on the basic reproductive ecology and biological resource management of Buccinum osagawai. Samples were collected from August 2018 to October 2019 with a drum-shaped net at a depth of 150–250 m along the continental shelf in Jumunjin, on the east coast of Korea. The species showed gonochorism and a lack of external sexual dimorphism. The overall sex ratio (F:M) was 1:1.2 (n = 549, F = 250, M = 299); as the size of the individuals increased, the proportion of males tended to decrease. The development pattern of the oocyte was synchronous, in which a dominant group of oocytes was identified within the same ovary. The size of the ripe oocyte was 82.3 (±22.6) × 125.5 (±22.0) μm. The spermatocyte development pattern was group-synchronous, in which multiple stages of germ cell populations were simultaneously identified within the same spermatogenic acinus. The gonad index (GI) for both males and females showed the highest value during June, after which it decreased sharply, and after August it was below 2.0. The main spawning season was from June to July, and the GI and stages of gonadal development did not show a pattern of seasonal changes. The main gonadal active season was from May to July, and both male and female gonadal development and maturation took place over a short period, whereas the recovery period after spawning was longer. At least 60.5% of the group, considering both males and females, showed maturity at 50.1 mm SH or more. Furthermore, the size of 50% group maturity was shown at approximately 50.0 mm SH.

Samples were collected from the subtidal region of Jumunjin on the eastern coast of Korea in July 2020. A total of 338 mussels of shell height (SH) 20.8-149.8 mm were used for sex ratio analysis. The sex ratio (F:M) in the same population of mussel Mytilus coruscus was approximately 1:0.7. The sex ratio according to the class of SH was different. The sex reversal pattern of M. coruscus appears to go from male → female → male → female, and as such is determined to be sequential hermaphrodites.

This study was carried out to obtain information on the developmental biology and the management of biological resources of the abalone Haliotis gigantea in Korea. The sex ratio (female:male) in the present study was 1:1.7 and the proportion of females was 36.6% (n=106/290). Their gonadal structures displayed definitive seasonal changes which were similar in pattern to the changes in the gonad index (GI). The GI showed a pattern of definitive seasonal changes in both males and females it was high in the fall and low in the spring. The reproductive cycle could be categorized into the following six stages: inactive, early active, late active, ripe, spent, and degenerative stage. Based on the monthly changes in GI and stages of gonadal development, October to November was determined to be the main spawning period for H. gigantea on Jeju Island, Korea.

Gonadotropin-releasing hormone (GnRH) is a key neuropeptide regulating reproduction in humans and other vertebrates. Recently, GnRH-like cDNAs and peptides were reported in marine mollusks, implying that GnRH-mediated reproduction is an ancient neuroendocrine system that arose prior to the divergence of protostomes and deuterostomes. Here, we evaluated the reproductive control system mediated by GnRH in the Pacific abalone Haliotis discus hannai. We cloned a prepro-GnRH cDNA (Hdh-GnRH) from the pleural-pedal ganglion (PPG) in H. discus hannai, and analyzed its spatiotemporal gene expression pattern. The open reading frame of Hdh-GnRH encodes a protein of 101 amino acids, consisting of a signal peptide, a GnRH dodecapeptide, a cleavage site, and a GnRH-associated peptide. This structure and sequence are highly similar to GnRH-like peptides reported for mollusks and other invertebrates. Quantitative polymerase chain reaction demonstrated that Hdh-GnRH mRNA was more strongly expressed in the ganglions (PPG and cerebral ganglion [CG]) than in other tissues (gonads, gills, intestine, hemocytes, muscle, and mantle) in both sexes. In females, the expression levels of Hdh-GnRH mRNA in the PPG and branchial ganglion (BG) were significantly higher at the ripe and partial spent stages than at the early and late active stages. In males, Hdh-GnRH mRNA levels in the BG showed a significant increase in the partial spent stage. Unexpectedly, Hdh-GnRH levels in the CG were not significantly different among the examined stages in both sexes. These results suggest that Hdh-GnRH mRNA expression profiles in the BG and possibly the PPG are tightly correlated with abalone reproductive activities.

This research reports the intersexuality of bivalves, such as Crassostrea gigas, Mytilus galloprovincialis, Rupiditapes philippinarum, Gomphina veneriformis and Barnea davidi discovered during the process of investigating the ecological health status of coastal waters of Korea. In intersex ovaries, the opposite germ cells were observed either individually or in groups in the interfollicular space and inside the oogenic follicle. Oocytes in the intersex testis were at the previtellogenic or initial vitellogenic stage. They were either scattered individually or in groups in the interfollicular space and inside the spermatogenic follicle. The intersexuality in C. gigas was 10.4% (n

This study was conducted to find out accumulated concentration of nickel, survival rate and falling rate, structural changes of abalone, Haliotis discus hannai exposed to nickel chloride. Experimental groups were composed of one control condition and five nickel chloride exposure conditions (5.9, 8.8, 13.3, 20.0, 30.0 mg/L). The accumulation of nickel in abalone was significantly increased all exposure group. Though the exposure groups had lower survival rate than the control group, higher falling rate than the control group. Histopathological changes in the foot, gill and hepatopancreas of abalone revealed obvious with exposure group than control group.

This study histologically describes the gonadal development and reproductive cycle of the abalone, Haliotis discus discus inhabiting Jeju Island of Korea. Gonads displayed histologically definitive seasonal changes. The gonad index (GI) of both females and males was the highest (3.2 and 3.3) in September and was the lowest (1.7 and 1.4) in January and February. Egg diameter increase from early stage in March and reach about 180?m to ripe stage in August. The condition index (CI) was highest in July and lowest in May. The pattern of changes in the GI, egg diameter and CI were similar to the pattern of seasonal changes in gonadal tissues. The female ratio (F/F + M) was 59% (n = 182:127). The reproductive cycle was divided into an inactive stage (January-February), early active stage (March-April), late active stage (May-July), ripe stage (August-October) and spent and degenerative stage (November-January). The main spawning period of H. discus discus was August to October at Jeju Island in 2014.