• Fisheries and Aquatic Sciences
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• 제14권1호
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• pp.11-15
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• 2011

We examined the effects of 17${\alpha}$-methyltestosterone (MT) on growth and induced sex change in the longtooth grouper Epinephelus bruneus. The growth rate for body weight (GRW) and specific growth rate (SGR) of the group injected with MT over 8 weeks were significantly higher than those of the sham-injected control group, the group injected over 4 weeks, and the control group. Of the orally administrated groups, the GRWs of the control group and the group given 1 kg of feed with 2.0 mg of MT were highest and did not significantly differ from one another. For SGR, the treatment groups differed significantly, and the SGR of the control group was higher than those of the other groups (P<0.05). The condition factor (CF) of the group injected over 4 weeks was higher than those injected over 8 weeks, the sham-injected control group over 8 weeks, and the control group. The CF did not significantly differ between the sham-injected control group over 8 weeks and the injected group over 8 weeks, but these two groups differed from the control group (P<0.05). The CFs of the groups given 1 kg of feed with 0.5, 1.0, and 2.0 mg of MT were significantly higher than that of the control group (P<0.05). The feed efficiency ratio was not significantly affected by MT administration. Most of the experimental groups receiving MT developed many unidentified germ cell cysts and perinucleolus oocytes, although neither spermazoa cells nor sex-changed males were observed in any of the treatments.

• 한국수산과학회지
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• 제45권1호
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• pp.17-24
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• 2012

We cloned and sequenced the cDNA encoding the $FSH{\beta}$ and $LH{\beta}$ subunits from the pituitary of the blacktip grouper Epinephelus fasciatus, which regulate vitellogenesis and maturation in vertebrates, to achieve stable and healthy gametes. The full-length cDNAs of $FSH{\beta}$ and $LH{\beta}$ were 571 bp and 617 bp, encoding 120 amino acid (aa) and 147 aa proteins, respectively. The deduced amino acid sequences of $FSH{\beta}$ and $LH{\beta}$ were highly homologous (68-97%) to those of other Perciformes; E. bruneus, Dicentrarchus labrax, Thunnus thynnus, and Pseudolabrus sieboldi. Phylogenetic analysis showed that the deduced $FSH{\beta}$ and $LH{\beta}$ amino acid sequences were categorized as a distinct subunit in the $GTH{\beta}$ family, and are closely related to the teleostei $FSH{\beta}$ and $LH{\beta}$, respectively. $FSH{\beta}$ and $LH{\beta}$ mRNA exhibited high abundance in the pituitary gland and low in other brain areas, but were not present in peripheral tissues, as determined by RT-PCR.

• 한국수산과학회지
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• 제50권5호
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• pp.527-533
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• 2017

We investigated the infection of nervous necrosis virus (NNV) in seven band grouper Hyporthodus septemfasciatus broodstocks, which have been reared in aquaculture farms in South Korea during 2012-2014. To investigate the prevalence of NNV within the broodstock, egg, sperm, and blood were sampled in the spawning season. The egg and sperm samples were subjected to a nested reverse transcription (RT) polymerase chain reaction (PCR) assay to detect NNV and were inoculated on SSN-1 cells to culture the virus. Blood samples were used to detect antibodies against NNV using enzyme linked immunosorbent assay (ELSIA). Positive values from ELISA were found in 39 of 162 samples (24%) in 2012, and 13 of 28 samples (46%) in 2014. Additionally, 4 of 34 broodstocks (11%) investigated in 2013-2014 were determined to be carriers from the nested RT-PCR and in vitro cultivation. The broodstocks in which antibodies against NNV were detected by ELISA, or in which NNV was detected by the nested RT-PCR assay, posed a risk of vertical transmission of NNV. Therefore, it is necessary to select virus-free broodstocks in seed production to reduce the possibility of the vertical transmission of NNV.

• 한국수산과학회지
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• 제35권3호
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• pp.237-241
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• 2002

This study was performed both to explore the host of nervous necrosis virus (NNV) between mariculturing fish species and to examine the phylogenic position of the NNV in Korea. NNV was confirmed on the basis of histopathological and molecular biological examination, then VNN infection was Preyed from either moribund or dead fishes including red drum, Sciaenops ocellatus; oblong rock fish, Sebastes oblongus and flounder, Paralichthys olivaceus. As a result of sequencing for a part of ms, virus from red drum was showed $98\%, $97\%, $86\% and $74\% homology with oblong rock fish, grouper, Japanese flounder and striped jack, respectively. On the other hand, NNV from oblong rock fish was demonstrated $96\%, $85\% and $72\% homology with grouper, Japanese flounder and striped jack, respectively. NNV from red drum and oblong rock fish was exhibited phylogenically distant from the representative NNV, SJNNV originated from striped jack. On the contrary, the viruses appeared to be similar species with Taiwan NNV isolated from culturing grouper.

• 한국발생생물학회지:발생과생식
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• 제20권2호
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• pp.81-90
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• 2016

The effect of sudden changes of water temperature (WT) on the survival rate and physiological responses of the red spotted grouper (Epinephelus akaara) were examined by manipulating WT control system for 9 days. Experimental condition was divided in two different regimes at low (from $10^{\circ}C$ to $4^{\circ}C$, decreased $1^{\circ}C/d$) and high (from $28^{\circ}C$ to $34^{\circ}C$, increased $1^{\circ}C/d$) WT. Survival rate of experimental fishes were observed, and determined the changes of hematological characteristics by analyzing plasma levels of cortisol, glucose, total protein, and electrolytes ($Na^+$, $Cl^-$, $K^+$). No mortality was observed until low WT $6^{\circ}C$ (144 h) and high WT $32^{\circ}C$ (96 h), and 100% mortality was observed at low WT $4^{\circ}C$ (216 h) and high WT $35^{\circ}C$ (171 h). Plasma levels of cortisol and glucose increased rapidly as decreasing WT, and the loss of swimming ability and respiration response was observed at low WT $7^{\circ}C$ and high WT $34^{\circ}C$ conditions.

• 한국발생생물학회지:발생과생식
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• 제20권2호
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• pp.65-79
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• 2016

We observed the osteological development of larval and juvenile red spotted grouper (Epinephelus akaara) in order to generate data for the assessment of skeletal deformities and to inform phylogenetic systematics research. Larvae and juveniles were obtained from a aquafarm in Muan-gun, Jeolla-namdo Province, Korea. The average water temperature at the time of breeding was $23.0^{\circ}C$ and average water salinity was 33.0 psu. Freshly hatched fish larvae had not undergone any ossification, but ossification of the parasphenoid bone, which forms the base of the cranium, occurred as the juveniles reached an average body length (BL) of 2.49 mm. At the same time, ossification of the preopercle and opercle occurred in the operculum, and ossification of the maxilla, which forms the upper jaw, and the dentary bones, which form the lower jaw, began. In addition, ossification of the vertebra occurred by formation of 7 vertebral centra and the neural spine in the abdominal vertebra. When the juveniles reached an average (BL) of 5.22 mm, ossification of the nasal, lateral ethmoid, and alisphenoid bones occurred in the cranium; ossification of the endopterygoid and metapterygoid bones began in the palatine region; and ossification of the hypohyal and interhyal bones occurred in the hyoid arch. At an average (BL) of 20.9 mm, ossification of the basisphenoid bone in the cranium and the suborbital bone in the orbital region occurred. Ossification of the vertebra then occurred by the formation of long pairs of ribs from the third to the ninth abdominal vertebrae, completing osteological development.

• 한국발생생물학회지:발생과생식
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• 제17권1호
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• pp.55-62
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• 2013

Puberty is the developmental period which animals obtain the ability of reproducing sexually for the first time in life. In commercially important aquaculture fish species, the onset of puberty is a matter of major interest due to controlling of sexual maturation to improve broodstock management. To investigate pubertal characteristics of female longtooth grouper (Epinephelus bruneus), specimens were classified into three groups by the bodyweight, including 1, 2, and 3 kg group. Thereafter, we focused on ovarian development and level changes of endocrine regulation factors (GnRH, GTHs, steroid hormone). In the non-breeding season (April), the levels of endocrine regulation factors showed increasing trends in accordance with bodyweight gaining; nevertheless, the oocytes were growth phase belongs to almost peri-nucleous stages in all groups. In the breeding season (June), the levels of endocrine regulation factors were fluctuated that decreases in levels of sbGnRH and $FSH{\beta}$ mRNA expressions along with serum $E_2$ concentrations in 3 kg of group. However, $LH{\beta}$ mRNA expression levels sustained increasing trends by the bodyweight. Moreover, the oocytes developed that 2 kg and 3 kg groups obtained plentiful vitellogenic oocytes while 1 kg group was still composed with greater part of pre-vitellogenic oocytes. Especially, the oocytes of 3 kg group reached over 450 ${\mu}m$ of diameters that indicating possibility to enter the final maturations. These results suggest that the progress of pubertal development in female E. bruneus could be classify into three phases via bodyweight, including pre-puberty (1 kg), early-puberty (2 kg) and puberty (3 kg).

• 한국발생생물학회지:발생과생식
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• 제23권1호
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• pp.35-42
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• 2019

Fish shows great difference in growth rate between individuals during larval development and early growth. This difference seriously reduces the production efficiency in fish culture. Growth hormone (GH)/Insulin-like growth factor 1 (IGF1) system is said to play some pivotal roles in fish growth. In this study, we investigated differences of GH, IGF1 and GHR gene expressions in juvenile red spotted grouper (Epinephelus akaara) with different growth performance. Red spotted groupers were reared under the same environmental condition (water temperature $24{\pm}1^{\circ}C$, natural light) for 96 days after hatching. They were divided into 3 groups by size (fast growing, middle growing and slow growing groups: FGG, MGG, and SGG, respectively). RNA was extracted from the brain, liver and muscle tissues from each group, and target gene expression was examined by real-time PCR. In the brain with pituitary gland, expression of GH gene in FGG was significantly higher than the expression in SGG, but the expression of IGF1 and GHR genes in the muscle was highest in SGG. Difference of GHR and IGF1 mRNA in the liver between groups with different growth performance was less clear than that in other tissues, although level of IGF1 mRNA was higher in SGG than in MGG. These results suggest that hormonal governing of growth is not the same in fast growing and slow growing fish, and size grading could cause a shift of hormonal state and growth pattern in this species.

• 한국발생생물학회지:발생과생식
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• 제23권2호
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• pp.139-148
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• 2019

Rising of water temperature due to global warming is a great concern to aquaculturists and fishery biologists. Hence, the present study aimed to investigate the effects of high water temperature on juvenile red spotted grouper, Epinephelus akaara based on the evaluation of stress responses in blood. E. akaara juveniles were exposed to different thermal conditions ($25^{\circ}C$, $28^{\circ}C$, $31^{\circ}C$, and $34^{\circ}C$) for 6 weeks following 2 weeks of acclimation at $25^{\circ}C$. Blood cell morphology and number were examined at three sampling points (2, 7, and 42 days) from a total of 180 fish. Major erythrocytic cellular abnormalities (ECA) observed in blood smears of thermally stressed groups ($31^{\circ}C$ and $34^{\circ}C$) after 6 weeks were echinocytes, teardrop-like cells, swollen cells and vacuolated cells. Both red and white blood cell number (RBC and WBC) were significantly (p<0.05) elevated in $31^{\circ}C$ and $34^{\circ}C$ group after 6 weeks thermal exposure. Differential leucocytes number showed significant increases in neutrophil (N) and decreases in lymphocytes (L) in the highest temperature ($34^{\circ}C$). Different N:L ratio was observed at different thermal conditions which can be used as a reliable alternative to measure stress response. Taken together, these results suggest that higher temperature ($31^{\circ}C$ and $34^{\circ}C$) can interfere the immune system of red spotted grouper by altering the blood cell morphology and number.

• 한국발생생물학회지:발생과생식
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• 제22권4호
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• pp.369-378
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• 2018

We determined the morphologic characteristics (body weight and degree of abdomen inflation) of the red spotted grouper, Epinephelus akaara, mother fish producing healthy eggs. Experimental fish were chosen from fish reared in a sea cage. The fish were divided into four size groups by body weight: 400~600, 600~800, 800~1,000, and 1,000~1,200 g and four stages (I~IV) of the degree of abdomen inflation. After hormone treatment, we observed the amount of ovulation-induced eggs, and rates of buoyancy, fertilization, embryonic survival, and hatching. As a result, mother fish with a body weight of 600 g or more spawned, and the fertilization rate, embryonic survival rate, and hatching rate were high in the 800~1,000 g range, thus showing effective ovulation induction. As a result of dividing the degree of abdomen inflation based on the anal fin of the mother fish into I-IV stages and determining hormone treatment time, the GSI was $0.9{\pm}0.2%$ at stage I, $2.3{\pm}0.2%$ at stage II, $5.6{\pm0.2%$ at stage III, and $7.9{\pm}0.9%$ at stage IV. The flotation rate and hatching rate were highest at stage III, and the fertilization rate and embryonic survival rate were highest at stage IV. Therefore, in terms of egg quality, the amount of eggs collected per mother fish, maturation, and histology were different depending on the degree of abdomen inflation. At stage III, where the abdomen inflation degree of the mother fish was based on the basal part of the dorsal fin relative to the height of the anal fin was 1, the egg quality was highest.