• Ocean and Polar Research
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• v.40 no.1
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• pp.15-22
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• 2018

In the present study, we investigated temporal variation in the reproductive effort and biochemical contents in adult Manila clam Ruditapes philippinarum at Shi-Heung-Ri beach on the east coast of Jeju Island. Gonad-somatic index (GSI), a ratio of the egg mass to the total biomass determined using ELISA increased dramatically from late May to June (7.1% to 19.5%). In mid-July, GSI dropped to 15.1%, indicating spawning on a small scale during this period. GSI also declined dramatically from late August (15.5%) to September (4.3%), suggesting that massive spawning occurred during this period. A positive correlation was observed between clam size and potential fecundity, while potential fecundity ranged between 1.19-8.40 million eggs/clam. Total proteins and lipids in the tissue increased from late spring to mid-summer, coinciding with an increase in GSI. Protein, lipid and carbohydrate contents in the tissue were lowest in January, indicating that clams were suffering from poor nutritional circumstances, which may be associated with poor food supply from the environment. Monthly increase and/or decrease in the body weight were closely related to gonad maturation and subsequent spawning, which was also linked to temporal changes in the contents of protein, lipid and carbohydrates in the tissue.

• Ocean and Polar Research
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• v.43 no.4
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• pp.365-370
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• 2021

Manila clam Ruditapes philippinarum is present at high rates of density in tidal flats in Cheonsu Bay on the west coast of Korea, where clams often exhibit mass mortalities in late summer. We monitored the pathologic condition of clams at Hwangdo tidal flat (HD) to understand the parasitic impacts on clam fitness. Manila clams were fully ripe in July and spawned during August and September, as the histology indicated. The histology revealed that clams in HD tidal flats were heavily infected by the protozoa parasite Perkinsus olseni, as the monthly prevalence ranged from 53% (September) to 93% (August). In addition, Manila clams were co-infected by the metazoan parasite Cercaria tapetis and Parvatrema duboisi with the prevalence of 0-33% and 0-14%, respectively. Massive hemocyte infiltration and subsequent inflammation were commonly observed from the gills of P. olseni infected clams. Clusters of P. olseni trophozoites and heavy hemocyte infiltration were also observed from the female gonad, suggesting that P. olseni interferes with host gonad maturation. The larval trematode occupied almost the entire host gonad, resulting in gonad castration. In addition, Metacercaria of P. duboisi were observed from the subsurface of the mantle. Ray's fluid thioglycollate medium assay (RFTM) indicated that clams collected in August and September contained approximately 4.0×106 P. olseni cells/g gills. Condition Index (CI) declined gradually from spring to early summer, and the decline in CI was interpreted as a consequence of the heavy parasitism, as the parasites drain the host's net energy to be used in somatic growth and gamete production.

• Animal cells and systems
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• v.16 no.4
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• pp.329-336
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• 2012

This study evaluated ecological health, using various biomarkers and bioindicators, of pale chub (Zacco platypus) as a sentinel species, in Daejeon Stream, South Korea, during AprilMay 2011. The biomarkers and bioindicators were compared among three sites of control: Reference ($C_z$), transition ($T_z$), and the urban zones ($U_z$); and the 7-Ethoxyresorufin-O-deethylase (EROD) activity, DNA damage, acetylcholinesterase (AChE) activity, and vitellogenin (VTG) concentrations were more significantly increased in the $U_z$ than in the $C_z$. Also, physiological markers such as condition factor, liver somatic index, visceral somatic index, and gonad somatic index were significantly increased in the $U_z$ than in the $C_z$. For the health assessments, three categorized parameters of blood chemistry, molecular biomarkers, and physiological bioindicators were standardized and calculated as a star-plot, representing values of Integrated Health Response (IHR). Values of IHR had more significant (P<0.05) increases in the $U_z$ than any other zones, indicating an impairment of ecological health by organic matter, nutrients (N, P), and toxic chemicals. This study is based on low levels of biological organization approach of molecular and physiological biomarkers and bioindicators, so further study of high-levels of biological organization approach such as community and population is required for overall range of health assessments. The approach of IHR values, however, may be useful in providing early warning of future impacts on ecological health.

• Korean Journal of Ichthyology
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• v.20 no.2
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• pp.81-89
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• 2008

An experiment was conducted for 80 days to determine the effect of feeding and starvation on the survival, growth, gonad-somatic index (GSI), hepato-somatic index (HSI), viscera index (LSI), the morphometric changes and hematological parameter in a cultured catfish, Silurus asotus. The survival and growth of the starved group was lower than those of the fed group during the experiment. Starvation resulted in retardation of growth, which provides examples of the reduction of final body weight, growth rate of body weight, specific growth rate and condition factor, whereas the fed group continued to grow and remained in good condition. Blood analysis (cortisol, glucose, aspartate aminotransferase, alanine aminotransferase, red blood cell and hemoglobin) showed significant differences between the fed and starved groups at the end of the experiment. These results suggest that all nutritional parameters used for starvation and feeding in this study appear to be a useful index of nutritional status in the cultured catfish.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.2
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• pp.188-192
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• 2018

The reproduction characteristics of hagfish Eptatretus burgeri were examined using individuals caught in the South Sea of Korea. The spawning season and size at minimum sexual maturity of this species were characterized based on a gonad-somatic index (GSI) and monthly variation egg size (long axis). From monthly variation of GSI, the spawning season was estimated to be from August to September. Developing eggs larger than 10 mm were found in March, and the largest egg size was found in July. The first spawning length was 34.2 cm TL. Batch fecundity ranged from 13 to 117 eggs for hagfish sized from 34.2 cm TL to 77.0 cm TL, respectively, and increased linearly with total length.

• Journal of Aquaculture
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• v.19 no.2
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• pp.133-139
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• 2006

The gossypol existed in cottonseed meal is a well known antispermatogenic agent which can impair reproductive performances of male fish as well as mammals. Two feeding experiments were conducted to examine a toxic effect of dietary supplementation of cottonseed meal on reproduction in juvenile olive flounder (the first experiment) for 19 weeks and growing olive flounder (the second experiment) for 26 weeks. After each feeding study, females and males were sampled for histological examination in gonads and liver to verify any negative effects by the dietary supplementation of cottonseed and soybean meal on reproduction. After two feeding trial, the gonad somatic index (GSI) of male and female (from the first feeding trial) were not significantly different among all the dietary treatments. The GSI values of female (from the second feeding trial) were not significantly different among all the dietary treatments. However, males fed cottonseed and soybean meal containing diets exhibited significantly lower GSI than that fed the control diet after the second feeding trial. Histological examination of gonads and liver of fish fed cottonseed and soybean meal did not show any negative effects compared to those of fish ffd the control diet. Hepatosomatic index of fish in the first and second feeding trials were not significantly different among all the dietary treatments. The findings in this study suggest that dietary supplementation of cottonseed and soybean meal up to 40% fish meal replacement might not deteriorate the gametogenesis of juvenile and growing olive flounder. However, the supplementation in diets over 30% fish meal replacement might reduce GSI of male in growing olive flounder.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.1
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• pp.37-43
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• 2012

We have investigated the effect of melatonin (MLT) on specific growth rate (SGR% $day^{-1}$), condition factor (k), gonado-somatic-index (GSI), histological structures of gonads, serum as well as gonadal protein and lipid in Nile tilapia Oreochromis niloticus. MLT treatment in the dose of 25 ${\mu}g/L$ for three weeks reduced SGR% $day^{-1}$ ($0.9{\pm}0.04$) as compared to control ($1.23{\pm}0.026$). The GSI value was significantly (p<0.05) reduced to $1.77{\pm}0.253$ from control where it was $2.56{\pm}0.25$. Serum protein level increased from $9.33{\pm}2.90$ mg/ml (control) to $11.67{\pm}1.45$ mg/ml after MLT treatment while there was depressed serum triglycerides ($86.16{\pm}1.078$ mg/dl) and cholesterol ($126.66{\pm}0.88$ mg/dl) as compared to control values where these were $123.0{\pm}1.23$ mg/dl and $132.0{\pm}1.65$ mg/dl respectively. Histological structure of ovary showed small eggs of early perinucleolus stage after MLT treatment while testicular structure of control and MLT treated fish was more or less similar. It is concluded that exogenous melatonin suppressed SGR% $day^{-1}$, GSI, ovarian cellular activity, protein and lipid biosynthesis, in tilapia suggesting that melatonin is useful in manipulating the gonadal maturity in fishes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.3
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• pp.246-252
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• 2012

The age and growth of the blackthroat seaperch Doederleinia berycoides was investigated based on samples captured in the southern seas of Korea from January to December, 2006. Age was estimated by analyzing otolith growth rings. The spawning period was extrapolated from August to November based on monthly changes in the gonad somatic index. The relationship between total length and otolith radius was analyzed separately for each sex with TL=-15.6174+10.3274R for females and TL=-4.4083+7.0749R for males. From the parameters calculated using average total length and weight when the year ring was formed, the growth of D. berycoides was expressed by von Bertalanffy growth equations as $L_t=34.71(1-e^{-0.2557(t+0.2078)})$, $W_t=713.85(1-e^{-0.2557(t+0.2078)})^{3.1972}$ for females, $L_t=27.37(1-e^{-0.3388(t+0.7362)})$, $W_t=353.91(1-e^{-0.3388(t+0.7362)})^{3.1647}$ for males, and $L_t=34.20(1-e^{-0.2530(t+0.2871)})$, $W_t=674.10(1-e^{-0.2530(t+0.2871)})^{3.1171}$ for pooled sexes, where L is total length at age t.

• Fisheries and Aquatic Sciences
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• v.17 no.1
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• pp.115-121
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• 2014

Eyestalk ablation (ESA) is commonly used in aquaculture to stimulate ovarian maturation in crustaceans, and methyl farnesoate (MF) affects crustacean molting and reproduction. To investigate the physiological effects of ESA and MF treatments on the shrimp Litopenaeus vannamei, we compared the effects of single eyestalk removal and MF injections. The ESA group had the lowest survival rate (50%), and individuals in the $0.1{\mu}g$ and $1.0{\mu}g$ MF-treated groups had survival rates of 80 and 73.3%, respectively. Conversely, molting numbers were highest in the ESA group, and similar to those of the 1.0-${\mu}g$ MF group. To investigate shrimp growth, we measured body weight during the experimental period and found that individuals in the ESA and $1.0{\mu}g$ MF groups showed significant increases in body weight. Furthermore, to investigate the effects of ESA and MF treatments on gonadal maturation, the gonad somatic index (GSI) was calculated after the experiment. All treated groups (ESA and MF) had higher GSI values than the control group, but the ESA and $1.0{\mu}g$ MF groups were not significantly different. Using histological ovary analysis, we determined that all treated groups showed indications of the previtellogenic stage, unlike the control group (immature stage). These results suggest that the high-MF-concentration treatment produced effects similar to those of ESA with respect to molting number, growth, and ovarian maturation.

• The Korean Journal of Malacology
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• v.28 no.2
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• pp.145-156
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• 2012

Larval development of the Manila clam Ruditapes philippinarum reared in an indoor tank system was examined in this study using light microscope and scanning electron microscope. To induce spawning and subsequent larval development, clams were collected from the intertidal zone at Gim-nyeong harbor in Jeju Island in August 2011. After 2 days of rearing in the tank, all Manila clams spawned in the midnight. Non-feeding trochophore larvae appeared 7hrsafter fertilization and the first D-shape larvae could be observed at 19 hrs. Twenty one days after fertilization the pediveliger larvae crawling on the bottom of the tank with well-developed foot were observed. Histology indicated that all the clams used in this study were in the ripe stage prior to spawning and the gonad-somatic index (GSI), a ratio of the egg mass to the tissue weight, of the ripe female measured by ELISA was 28.6%. The GSI of female clam declined to 17.3% after the massive spawning in the tank, suggesting that Manila clam discharged 40% of the total eggs during the first spawning event. In conclusion, spawning and subsequent larval development of Manila clam was successfully carried out in this study using an indoor tank system, and the information obtained in the present study could be useful in future Manila clam hatchery development.