• Fisheries and Aquatic Sciences
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• v.19 no.9
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• pp.41.1-41.7
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• 2016

Background: The transgenic approach using estrogen-responsive regulator in fish has been given much attention as a potential means to detect and/or address estrogen-related aquatic pollutions. In order to address the development stage- and reproduction status-dependent expression patterns of the chgH-rfp transgene (red fluorescent protein transgene driven by choriogenin H promoter) in marine medaka Oryzias dancena, naturally occurring red fluorescent protein (RFP) signals under non-exposed conditions as well as the transgenically induced RFP signals under estrogen-exposed conditions were assayed. Results: Female transgenics begun to show naturally occurring RFP signals from the age of 7 weeks post hatching (WPH) without experimental estrogen exposure. Afterward, these RFP signals in female transgenics became robust with the progress of ovarian maturation. On the other hand, male transgenics did not show any naturally occurring RFP signal under non-exposed conditions irrespective of developmental stages and maturation statue. Upon exposures using estradiol-$17{\beta}$ (E2) and $17{\alpha}$-ethinylestradiol (EE2), RFP signals were significantly induced specifically in the livers of transgenic males. Conclusions: Male chgH-rfp transgenics were able to keep the "off" state of RFP expression during their entire life cycle unless exposed to exogenous estrogens. Owing to their tight regulation capability of estrogen-responsive transgene, transgenesis of chgH-rfp in male marine medaka could offer a useful model system for future ecotoxicogenomic studies regarding estrogenicity-related issues in aquatic and marine environments.

• ALGAE
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• v.26 no.1
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• pp.41-50
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• 2011

Yellow Sea surface sediment samples collected on October 15-31, 2003 were analyzed using the palynological process to investigate the spatial distribution of dinoflagellate resting cysts. The sampling areas comprised four latitudinal transects, the northernmost of which was located off the Shandong Peninsula, China and the southernmost off Jeju Island, Korea. Each transect line was composed of six to nine stations, spanning the distance between the Chinese and Korean coasts. Twenty-five different types of dinoflagellate cysts were identified. Gonyaulax scrippsae, Alexandrium spp. (ellipsoidal type), and G. spinifera were the most dominant at all stations surveyed. Dinoflagellate cysts belonging to the Gonyaulacales comprised over 50% of all cysts collected. The latitudinal distribution trend showed that cyst concentrations along the two middle transects were much higher than those along the two northern and southern transects. Cyst concentrations in the offshore central areas reached their highest values within each transect and gradually decreased toward the Chinese and Korean coasts. Overall, cyst concentrations were markedly elevated in the offshore central Yellow Sea areas and gradually decreased outward in all four directions. This concentric cyst distribution pattern was consistent with the hydrographic features of the Yellow Sea, such as circular current systems, sedimentary properties, and water depth.

• Fisheries and Aquatic Sciences
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• v.20 no.9
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• pp.23.1-23.9
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• 2017

Two distinct cDNAs encoding aquaporins (mmAQPs 1a and 3a) were isolated and characterized from mud loach Misgurnus mizolepis. The identified mud loach AQP cDNAs encode for polypeptides of 260 and 302 amino acids. Topology predictions confirmed six putative membrane-spanning domains connected by five loops and the N- and C-terminal domains being cytoplasmic. The mud loach AQPs 1a and 3a showed broad distribution in multiple tissues including immune-responsive tissues as well as osmoregulatory tissues. Hence, the diversity of AQP distribution and expression possibly indicated its differential functions in the regulation of fluid movement in response to environmental stimuli. The transcription of mmAQP genes was differentially modulated by immune challenges. In particular, the mmAQP3a expression level in the liver was more responsive to immune challenges than that of mmAQP1a. Taken together, fish stimulation or infection resulted in significant modulation of mud loach AQP genes, suggesting potential functional roles of these proteins in piscine pathophysiological process.

• Asian-Australasian Journal of Animal Sciences
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• v.24 no.7
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• pp.974-981
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• 2011

This study was designed to re-evaluate the dietary methionine requirement by means of the plasma methionine and ammonia concentrations in surgically modified rainbow trout, Oncorhynchus mykiss. A total of 35 rainbow trout averaging $505{\pm}6.5$ g (initial body weight, mean${\pm}$SD) were randomly distributed into seven groups with five fish in each group. After 48 h of feed deprivation, each group of fish was fed one of seven L-amino acid based diets containing 0.5% cystine and graded levels of methionine (0.25, 0.40, 0.50, 0.60, 0.70, 0.80 or 0.95% of diet, dry matter bases) by intubation at 1% body weight on dry matter basis. Blood samples were taken at 0, 5 and 24 h after intubation. Post-prandial plasma free methionine concentrations (PPmet, 5 h after intubation) and post-absorptive plasma free methionine concentrations (PAmet, 24 h after intubation) of fish fed diets containing 0.60% or higher methionine were significantly (p<0.05) higher than those of fish fed diets containing 0.50% or lower methionine. PPmet and PAmet in fish fed diets containing 0.60% or higher methionine were not significantly different except PPmet of fish fed diet containing 0.95% methionine. Post-prandial plasma ammonia concentrations (PPA, 5 h after intubation) of fish fed diets containing 0.70% or higher methionine were significantly higher than those of fish fed diets containing 0.60% or lower methionine, and PPA of fish fed diets containing 0.25 and up to 0.60% methionine were not significantly different from each other. Broken-line model analyses on PPmet, PAmet, and PPA indicated that the dietary methionine requirement of rainbow trout was between 0.59 (1.69) and 0.67 (1.91) % of diets (% dietary protein bases) when the diets contained 0.5% cystine.

• Development and Reproduction
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• v.14 no.2
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• pp.59-63
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• 2010

This study was performed to examine the influence of water temperature on egg developmental speed for determining the required time and optimum water temperature for hatching of olive flounder Paralichthys olivaceus eggs. The fertilized eggs were collected from the naturally spawned adults in November 2007. The eggs were randomly divided into 6 groups of temperature (5, 10, 15, 20, 25 and $30^{\circ}C$) and transferred in $1{\ell}$ beaker, respectively. The fertilized eggs of the olive flounder did not hatched at $5^{\circ}C$ and $30^{\circ}C$ and hatching rates at 10, 15, 20 and $25^{\circ}C$ were 3, 12, 25 and 50%, respectively. The relationships between the water temperature (T, $^{\circ}C$) and required time (1/t, hour) from egg to each developmental stage were given as follows ; Blastula: 1/t=0.0208T-0.0951 ($r^2$=0.8593) Kupffer's vesicle: 1/t=0.0052T-0.0176 ($r^2$=0.9819) Myotome: 1/t=0.0034T-0.0172 ($r^2$=0.8508) Hatching: 1/t=0.0016T-0.0068 ($r^2$=0.9915) Biological minimum temperature in egg development was calculated to be $4.3^{\circ}C$.

• Fisheries and Aquatic Sciences
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• v.23 no.1
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• pp.2.1-2.6
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• 2020

Background: As the cost of fishmeal continues to rise, there will be a need to optimize the diet by minimizing dietary fishmeal inclusion in aquafeed. In this study, a 7-week experiment was conducted to evaluate soybean meal, fermented soybean meal (soytide), and sesame meal as fishmeal replacers in whiteleg shrimp, Litopenaeus vannamei. Methods: A 30%-based fishmeal diet was considered as control (CON), six other diets were prepared by replacing 20% or 40% of fishmeal with soybean meal (SB₂₀ and SB₄₀), fermented soybean meal (ST₂₀ and ST₄₀), or sesame meal (SM₂₀ and SM₄₀) from the CON diet. Twenty shrimp with average initial weight of 0.65 ± 0.05 g (mean ± SD) were randomly distributed into 21 tanks (45 L) and fed four times a day. Water temperature was controlled at 28 ± 1 ℃ and aeration was provided by air stones. Results: Weight gain, specific growth rate, feed efficiency, and protein efficiency ratio of shrimp fed CON showed no significant differences compared to shrimp fed all the other diets. However, growth performance of shrimp fed ST₂₀ diet was significantly higher than those of shrimp fed the SM₂₀ and SM₄₀ diets (P < 0.05). Superoxide dismutase activity (SOD) of shrimp fed CON, ST₂₀, and ST₄₀ diets was significantly higher than those of shrimp fed the SB₄₀ and SM₄₀ diets. But there were no significant differences among shrimp fed CON, SB₂₀, ST₂₀, ST₄₀, and SM₂₀ diets. Also, lysozyme activity of shrimp fed ST₂₀ diet was significantly higher than those of shrimp fed the SB₄₀ and SM₄₀ diets. Although, lysozyme activity of shrimp fed the CON diet was not significantly different compared to shrimp fed all the other experimental diets. Conclusions: Therefore, SB, ST, and SM could replace 40% of fishmeal based on growth performance and lysozyme. According to the SOD activity, SB and SM could replace 20% of fishmeal and ST could replace 40% of fishmeal in juvenile whiteleg shrimp Litopenaeus vannamei.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.6
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• pp.753-760
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• 2013

Two feeding trials were conducted to investigate the effects of feeding rate and frequency on growth performance and body composition of juvenile Korean rockfish Sebastes schlegeli reared at $15.0{\pm}0.3^{\circ}C$. In the first trial, three replicate fish groups averaging $2.07{\pm}0.03g$ were fed a commercial diet with one of seven different daily feeding rates: 1.00%, 2.00%, 2.50%, 2.75%, 3.00%, 3.25%, and satiation (3.34%) based on body weight (BW). After four weeks of feeding, fish fed the 3% diet showed significantly higher weight gain (WG) and feed efficiency (FE) than fish that received the other feeding rates. In the second trial, the optimum feeding frequency was evaluated with three replicate fish groups averaging $2.04{\pm}0.03g$. Fish were fed a commercial diet at 2.87% BW with six different daily feeding frequencies: 2, 3, 4, 5, 7, or 9 meals. After four weeks of feeding, WG, specific growth rate, FE, and protein efficiency rate in fish fed 3 meals $d^{-1}$ were significantly higher than those of fish fed 7 or 9 meals $d^{-1}$. In both feeding trials, proximate composition of the entire body changed depending on the feeding rate or frequency. A broken-line regression analysis based on weight gain suggested that the optimum daily feeding rate and frequency for juvenile Korean rockfish at $15^{\circ}C$ was 2.9% BW $d^{-1}$ and 2-3 meals $d^{-1}$, respectively.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.10
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• pp.1478-1486
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• 2014

The present experiment was conducted to evaluate the efficacy of dietary fermented by-product of mushroom, Pleurotus ostreatus, (FBPM) as a fish meal (FM) replacer in juvenile Amur catfish, Silurus asotus. A total number of 225 fish averaging $5.7{\pm}0.1g$ ($mean{\pm}standard$ deviation) were fed one of the five experimental diets formulated to replace FM with FBPM at 0%, 5%, 10%, 20%, and 30% ($FBPM_0$, $FBPM_5$, $FBPM_{10}$, $FBPM_{20}$, and $FBPM_{30}$, respectively). At the end of eight weeks of the experiment, average weight gain (WG) of fish fed $FBPM_0$ or $FBPM_5$ were significantly higher than those of fish fed $FBPM_{20}$ or $FBPM_{30}$ diets (p<0.05). However, there was no significant differences in WG among the fish fed $FBPM_0$, $FBPM_5$ or $FBPM_{10}$, and between fish fed $FBPM_{10}$ or $FBPM_{20}$, and also between those fed $FBPM_{20}$ or $FBPM_{30}$ diets. Lysozyme activity of fish fed $FBPM_0$ or $FBPM_5$ were significantly higher than those of fish fed $FBPM_{10}$, $FBPM_{20}$ or $FBPM_{30}$ diets (p<0.05). The chemiluminescent response of fish fed $FBPM_5$ was significantly higher than those of fish fed $FBPM_0$, $FBPM_{20}$ or $FBPM_{30}$ diets (p<0.05). Broken line regression analysis of WG suggested that the maximal dietary inclusion level for FBPM as a FM replacer could be 6.3% without any adverse effects on whole body composition and on serological characteristics. Therefore, these results may indicate that the maximal dietary inclusion level of FBPM as a FM replacer could be 6.3% in juvenile Amur catfish.

• Fisheries and Aquatic Sciences
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• v.19 no.5
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• pp.24.1-24.6
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• 2016

We determined the optimum dietary protein level in juvenile barred knifejaw Oplegnathus fasciatus in cages. Five semi-purified isocaloric diets were formulated with white fish meal and casein-based diets to contain 35, 40, 45, 50, and 60 % crude protein (CP). Fish with an initial body weight of $7.1{\pm}0.06g$ ($mean{\pm}SD$) were randomly distributed into 15 net cages (each size: $60cm{\times}40cm{\times}90cm$, $W{\times}L{\times}H$) as groups of 20 fish in triplicates. The fish were fed at apparent satiation level twice a day. After 8 weeks of feeding, the weight gain (WG) of fish fed 45, 50, and 60 % CP diets were significantly higher than those of fish fed 35 and 40 % CP diets. However, there were no significant differences in WG among fish fed 45, 50, and 60 % CP diets. Generally, feed efficiency (FE) and specific growth rate (SGR) showed a similar trend as WG. However, the protein efficiency ratio (PER) was inversely related to dietary protein levels. Energy retention efficiency increased with the increase of dietary protein levels by protein sparing from non-protein energy sources. Blood hematocrit content was not affected by dietary protein levels. However, a significantly lower amount of hemoglobin was found in fish fed 35 % CP than in fish fed 40, 45, 50, and 60 % CP diets. Fish fed 60 % CP showed the lowest survival rate than the fish fed 35, 40, 45, and 50 % CP diets. Broken-line analysis of WG showed the optimum dietary protein level was 45.2 % with 18.8 kJ/g diet for juvenile barred knifejaw. This study has potential implication for the successful cage culture of barred knifejaw.

• Development and Reproduction
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• v.23 no.4
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• pp.333-344
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• 2019

In vertebrate reproductive system, estrogen receptor (ER) plays a pivotal role in mediation of estrogenic signaling pathways. In the present study, we report the cDNA cloning, expression analysis, and transcriptional activity of ERβ1 subtype from medaka Oryzias dancena. The deduced O. dancena ERβ1 (odERβ1; 519 amino acids) contained six characteristic A/B to E/F domains with very short activation function 2 region (called AF2). A phylogenetic analysis indicated that odERβ1 was highly conserved among teleost ERβ1 subgroup. A conventional RT-PCR revealed that the odERβ1 transcripts were widely distributed in the multiple tissues, the ovary, brain, gill, intestine, kidney, and muscle. Further, the relatively higher odERβ1 expressions in the ovary and brain were clearly reproduced in RT-qPCR assay. When HA-fused odERβ1 expression vector was transfected into HEK293 cells, an immunoreactivity for odERβ1 was mainly detected in the nucleus part. Finally, an estrogen responsive element driven luciferase reporter assays demonstrated that the transcriptional activity of odERβ1 significantly increased by estradiol-17β (E2) in a dose dependent manner (p<0.05). However, fold-activation of odERβ1 in the presence of E2 was markedly weak, when it compared with those of O. latipes ERβ1. Taken together, these data suggest that odERβ1 represents a functional variant of teleost ERβ subtype and provides a basic tool allowing future studies examining the function of F domain of ERβ1 subtype and expanding our knowledge of ERβ evolution.