To verify the sex steroids which are involved in oocyte maturation of the blacktip grouper, , we incubated vitellogenic oocytes (0.41 and 0.50 mm in average diameter) in the presence of exogenous steroid precursor (-hydroxyprogesterone). Steroids were extracted, separated and identified by thin layer chromatography. The major metabolites produced were androstenedione, estradiol-, estrone and progestogens. Progestogen metabolites in the oocytes of 0.50 mm were more abundant than those of 0.41 mm. Also, we investigated the effects of human chorionic gonadotropin (HCG; 5, 50 and 500 ), -dihydroxy-4-pregnen-3-one () and -trihydroxy-4-pregnen-3-one (; 5, 50 and 500 , respectively) on oocyte maturation. In the oocytes of 0.41 mm, treatment with 50 IU HCG stimulated GVBD () compared with controls (, <0.05). In the oocytes of 0.50 mm, treatment of (50 and 500 ) stimulated GVBD ( and , respectively) compared with controls (, <0.05). Treatment with 500 IU HCG also stimulated GVBD () compared with controls (<0.05). Taken together, these results suggested that both HCG and were effective on in vitro oocyte maturation and may act as a maturation inducing hormone in blacktip grouper.

Light characteristics are very specific in the aquatic environment. Fish vision and different light spectra perception are related to each species’ natural habit. Light is one of the main environmental conditions and can be easily manipulated in artificial rearing settings. Cholecystokinin (CCK) and mucus-secreting goblet cells are the main regulators of digestion. In this study, we established whether the light spectrum (natural condition, full spectrum: green, 520 nm; red, 590 nm, and blue, 480 nm) influences growth performance and digestive activity related to CCK mRNA expression and mucus-secreting goblet cell activity in order to develop a good management protocol and optimal rearing system for the longtooth grouper. For each light spectrum, fish were reared 12 weeks under a flow-through system and fed commercial pellet diets once daily. At the end of the experiment, the final body weights differed among the fish reared under different light spectra. The highest growth performance value was observed in fish reared under the green light condition. On the other hand, the growth performances of fish in the natural and blue light conditions were drastically decreased in last 3 weeks of the experiment. CCK mRNA expression and mucus-secreting goblet cell activity were significantly higher in the fish under green light condition than in the fish under the natural, red, and blue light conditions. Rearing of the longtooth grouper under the green light condition had positive effects on fish growth performance and digestion. We recommend that the appropriate light spectrum for the artificial culture of the longtooth grouper is the green light condition from the perspective of growth performance and the synergistic effects of CCK and mucus-secreting goblet cells. However, longer light treatment periods are needed in future investigations to clarify the effects of light spectrum on the longtooth grouper. Together with the findings of the present study, such studies would result in better understanding of the digestive physiology and contribute to the development of optimal rearing management for commercial production of the longtooth grouper.

The transcription factors, DMRT1 and FOXL2, play a role in fish sex differentiation of the bipotential precursor into the male and female pathway, respectively. In order to provide the molecular background for understanding hormonal regulation in sexual determination and differentiation in the red-spotted grouper, Epinephelus akaara, one of commercially important epinephelines, and is often used to study protogynous sex change. First, we amplified the partial sequence of two genes (DMRT1 and FOXL2) from the gonad of red-spotted grouper. Also, we surveyed the tissue-specific and sex-specific expression pattern of each genes by RT-PCR. The effects of 17α-methyltestosterone (MT) in the sexually immature gonad of red-spotted grouper were investigated by Real-time quantitative RT-PCR. Fish were treated with MT-dipping method from around 70 days after hatching (DAH) for two month. DMRT1 and FOXL2 cDNA flagments consist of 489 and 836 base pairs (bp) and encodes a protein of 162 and 278 amino acids, respectively. RT-PCR revealed that DMRT1 mRNA was expressed higher level in the testis. Foxl2 was expressed extensively in the neural and peripheral tissues with its highest level in the ovary, indicating a potential role for Foxl2 in the brain-pituitary-gonad axis. Real-time quantitative RT-PCR analyses showed that DMRT1 mRNA expression was upregulated in the MT-treated fish. These results suggest that the sex inversion of red-spotted grouper by MT might be due to the suppression of FOXL2 gene expression, and resulting in the induction of the 11-KT secretion.

This study is to survey the ultrastructure of gamete cells and micropyle of pre-fertilized and post-fertilized eggs after HCG hormone treatment by transmission and scanning electron microscopy (TEM and SEM) in E. akaara, E. bruneus and E. septemfasciatus. These fishes are economical importance species for Jeju coastal area resources. In spite of its an importance resources, details studies on the ultrastructural aspects of gamete cells for its reproductive biology have not been undertaken. Morphological features of ovulation process have been studied during its normal occurrence in the reproductive cycle of these fish by light microscopy. Moreover, it has been studied for many years to induce spawning by environmental factors (day length, water temperature etc) or injection of HCG for ovulation in these species. Studies on the micropyle was mainly focused on the eggs of insects, fresh water and a few sea water fishes. Micropylar structure of fish displays morphological characteristics of interspecies-specific by inhabitant environment and spawning feature. On the other hand, it is an importance cue for a taxonomical indicator and identification fish eggs. SEM studies were performed on growing and mature oocytes obtained by stripping and cannulation from 3 grouper species sampled between July and August in spawning season. The outer layer of chorion of preovulatory growing stage oocytes could be divided into four layers; zona pellucida, follicular cell layers consisted of granulosa and thecal cells layer and the most outer ovigerous lamella. Ovulation process of mature stage oocytes initiated by rupture of ovigerous lamella and ovulated by contraction of follicular cell layers. Besides, the micropylar shape of ripe stage oocytes in E. akaara, E. bruneus and E. septemfasciatus presented volcano or crateriform-like cylindrical form. Internal structure of micropylar vestibule displayed cylindrical clockwise 8 or 10 spiral arrangement structure in these species. The micropyle diameter and apparatus at the animal pole differ significantly among the 3 species. The difference in their diameters suggests species-specific in the correlation between spermatozoal head size and micropylar diameter for polyspermy prevention and hybridization during fertilization. Besides, after artificial fertilization, the vestibule morphologically transformed into dom-shape and pillar-shape for fertilization cone formation. Pores of various sizes in the 3 grouper species were somewhat regularly distributed in concentric circles only around the micropyle. In particular, large pores had numerous gill filament-shaped projections connected to oolemma. These structures are suggested to be related to gas exchange, osmoregulation, and micronutrient influx or efflux between eggs and water during fertilization and egg development. In addition, spermatozoa ultrastructure was examined in 3 grouper species. TEM investigation revealed that, in all species, spermatozoa display a round head, a nucleus containing highly condensed, filamentous chromatin clusters, no acrosome, a short midpieces consisting of numerous mitochondria and the proximal and distal centrioles and a flagellum exhibiting the typical axoneme structure (9+2). Especial, both E. akaara and E. bruneus display regular laternal fins in flagella, but in E. septemfasciatus, no fins in flagella with hook shape tails.

We investigated the androgenic effects of 11-ketotestosterone (11-KT) on gonadal sex reversal and spermatogenesis in honeycomb grouper Epinephelus merra by method of gonadal biopsy. 11-KT was injected intramuscularly at a concentration of 1 and body weight. The proportion of cross sectional area of the gonad occupied by each germ cell type was measured and compared pre- and post-injection group. During the sex change phase, the distribution ratio of oocytes was decreased in all fish of 11-KT treatment group while the distribution ratio of spermatocytes was increased than pre-injection group. In male phase, all fish of 11-KT treatment group shown the increased distribution ratio of spermatocytes, but the distribution ratio of spermatozoa was decreased than pre-injection group. The present results suggest that 11-KT can stimulate degeneration of oocytes, proliferation of spermatocytes and spermiation in honeycomb grouper.

이 연구는 실내 사육수조에서 자연산란 후 수정된 난을 대상으로 수온에 따른 난 발생속도와 부화율을 조사하였다. 부화에 이르기까지 각 수온조건에서 소요된 시간은 에서 상실기 이후 발생이 진행되지 않았고, 18, 21, 24, 에서 각각 70시간 30분, 44시간 10분, 29시간 10분 그리고 24시간 30분이 소요되었다. 부화율은 에서 0%였고, 18, 21, 24 그리고 에서 각각 , , 그리고 로 뚜렷한 차이 없이 에서 다소 높았고 21와 에서 비슷

2000년 2월부터 2001년 2월까지 남태평양 미크로네시아 군도의 Chuju 연안에 서식하는 주Epinephelus merra 암컷을 대상으로 생식주기를 조사하였다. 생식소숙도지수 (GSI)는 2월부터 증가하기 시작하여 3월에 최고치 (3.410.84)를 보였다. 조직학적 관찰결과 3월과 4월의 난소 안에는 난황을 가진 다양한 단계의 난모세포와 배란여포들이 존재하였다. 6월부터 1월에 난소 안에는 미성숙 난모세포만 있었다. 이들 결과로 E. merra