• Journal of Aquaculture
• /
• v.20 no.1
• /
• pp.47-50
• /
• 2007

The primordial germ cells of the oblong rockfish, Sebastes oblongus were buried under fibrous mesenchymal tissues between gut and mesonephric duct of pre-larva with 4.0 mm total length (TL) at 1 day after the parturition. In the juvenile of 22.0 mm TL at 71 days after the parturition, the gonad composed of a large number of gonial cell and formed of cavity along the lateral side of the gonad, differentiated to the ovary. At this time, the gonad formed seminiferous tubules by somatic cells, was differentiated to the testis. The smallest oblong rockfish that possessed primary oocytes was about 42.1 mm TL at 141 days. Spermatogonia remained quiescent until most fish were over 42.1 mm TL at 141 days. The oblong rockfish the differentiated directly into male or female without an intermediate female phase at the early indifferentiated stage. Therefore, the oblong rockfish belongs to the differentiated type of gonochoristic teleosts.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.29 no.1
• /
• pp.44-50
• /
• 1996

Sex differentiation in the rockfish, Sebastes schlegeli, was studied by using a histological method for the appearance of primordial germ cell, formation of primitive gonad and differentiation of female and male. The primordial germ cells were buried under fibrous mesenchymal tissue between gut and mesonephric duct of pre-larva with a total length (TL) of 6.3 mm at 2 days after parturition. In juvenile of TL $5.2\~5.9cm$ at 65 days after parturition, the gonad composed of a large number of genial cell and formed of cavity along the lateral side of the gonad, differentiated to the ovary. At this time, the gonad formed seminiferous tubules by somatic cells, differentiated to the testis. In juvenile of TL $7.0\~7.2cm$ cm at 115 days after parturition, gonads divided into testis contained pigment cell and ovary absent pigment cell. S. schlegeli differentiated directly into male or female without an intermediate female phase at early indifferentiated stage. Therefore, S. schlegeli belongs to the differentiated type of gonochoristic teleosts. At 350 days after parturition, sex ratio was approximately 1 : 1(p>0.05).

• Korean Journal of Ichthyology
• /
• v.21 no.3
• /
• pp.141-148
• /
• 2009

Sex differentiation and gonad development were investigated in a marine medaka species, Oryzias dancena (Beloniformes; Teleostei). The average time to hatch was 11 days post-fertilization (dpf) at $25^{\circ}C$. Primordial germ cell (PGC) was first observed at 5 dpf and migrated to presumptive gonadal area between the gut and pronephric duct at 9 dpf. Male and female gonads were morphologically differentiated at 12 days post-hatching (dph). Early oocytes at perinucleolus stage as well as the formation of spermatid and efferent duct were observed at 28 dph. At 6 weeks of age, the ovary exhibited yolk granulation in many oocytes, while testis possessed a considerable number of spermatogonia and spermatids. The first ovulation was observed in 9-week-old females, and at the same age, males contained fully-matured spermatozoa. Data obtained in this study indicate that the gonad differentiation of O. dancena is the typical type of differentiated gonochorism.

• Korean Journal of Ichthyology
• /
• v.2 no.1
• /
• pp.95-105
• /
• 1990

Gonadal sex differentiation of Misgurnus mizolepis was studied during growth from the size of 3.5 mm (2-day old) larvae to about 80 mm in total length (100-day-old) adult fish. One pair of primordial germ cells were found 2 days after hatching, and the development of prominent genital ridge was noticed at both stages of 4 days and 5 days after hatching. The gonadal sexes of this species were clearly distinguishable in 8 days, when the fry reached 15. 0 mm in total length. Spermatids first appaered at the stage of 20 days after hatching and 100-day-old female fish had well-developed ovaries. Above results indicate that M. mizolepis belongs to the differentiated type of gonochoristic teleosts.

• Journal of Aquaculture
• /
• v.13 no.3
• /
• pp.215-222
• /
• 2000

The primordial germ cell of the sweet fish was recognized from the 2-day old fry (tl : 0.66 cm), when it began to protrude into peritoneal cavity between meaonephric duct and gut. The primordial gonad, with the formation of genital ridge, developed on the 30-day old fry. Ovarian differentiation was identified by the presence of ovarian cavity and meiotic oocytes from the 90-day old fry (tl : 3.42 cm). Testicular differentiation was identified by the presence of spermatogonial cells with efferent duct from the 100-day old fry (11 : 4.50 cm). Hence the sweet fish belongs to the differentiated type of gonochoristic teleost.

• Korean Journal of Ichthyology
• /
• v.13 no.4
• /
• pp.248-253
• /
• 2001

An histological study was conducted to determine the initial treatment time and treatment duration in the use of sex-reversal hormones in relation to gonadal development and sexual differentiation in the bagrid catfish, Leiocassis ussuriensis. The primordial germ cell, which could be recognized from one-day-old fry, began to protrude into the peritoneal cavity between the mesonephric duct and the gut. The primordial gonad with a genital ridge was developed at 5~10 days after hatching. Sex differentiation of the ovary was identified by the ovarian cavity and meiotic oocytes from 20-day-old larvae. Testicular differentiation was also identified by spermatogonial cells from 20-day-old larvae. It may therefore be concluded that this species belongs to the differentiated type of gonochoristic teleost.

• Development and Reproduction
• /
• v.2 no.1
• /
• pp.69-74
• /
• 1998

The early gonadal development and sexual differentiation of Rhynchocypris oxycephalus are described from the stage of hatching to 150 days after hatching. During this peroid, the average length of the body grew from 0.64 cm to 5.96 cm. the primordial germ cells (PGCs), which could be recognized at the time of hatching, began to protrude into peritoneal cavity at a standard total length of 1.91 cm. At a standard total length of 2.29cm, initial ovarian differentiation wasidentified by the transformation of PGCs to meiotic oocytes. Finally, at the standard total length of 5.96 cm, the female gonads gradually developed towards migratory nucleus oocytes, characterisiing the maturation. Oocytes proliferated rapidly after sex differentiation while the testis entered a period of quiescence, as they continued to multiply but did not undergo growth until the standard total length of 4.00 cm. At a standard total length of 4.00 cm, spermatocytes arrested in thephase of interkinesis, Sertoli-like cells and sperm duct formation, with signs of meiotic activity, were observed. Therefore it may be concluded that R. oxycephalus belongs to the differentiated type of gonochoristic teleosts.

• Journal of Aquaculture
• /
• v.18 no.2
• /
• pp.76-80
• /
• 2005

The early gonadal development and sex differentiation of the mandarin fish, Siniperca scherzeri was described from hatch to the 130th day post-hatch (DPH). Primordial germ cells were observed on the just hatched fry (5.10 mm in total length (TL)) and began to protrude into the peritoneal cavity between mesonephric duct and gut. The primordial gonad, with the formation of genital ridge, developed on the 8-10th DPH (10.77-12.47 mm TL). Ovarian differentiation was identified by the presence of ovarian cavity and meiotic oocytes from the 40th DPH (29.75 mm TL). Testicular differentiation was identified by the presence of spermatogonial cells with efferent duct also from the 40th DPH. Sex differentiation of the mandarin fish was identified as gonochoristic type.

• Journal of Aquaculture
• /
• v.11 no.4
• /
• pp.529-546
• /
• 1998

Gonadal part that developed by indifferentiation period for 6 months after hatching is made as gonad and fat body. These gonad are thin semi-transparant and undistinguished germ cell. Germinal epithelium is distinguished by development of gonad epithelial tissue from 7 months after hatching. Sex differentiation is begun by oogonia develoment at 8 months after hatching. Primary oocytes grow over germinal epithelium of gonadal cavity, at 9 months after hatching, gonadal cavity become ovarian cavity as they increasing. As soon as oocytes at 13 months after hatching are filled with the whole part of gonad, degeneration of oocyte is begun. And then, gonad has cavity tissue, a small number of oocyte are located in gonadal cavity. At 15 months after hatching, new primary oocyte develop and cavity of ovarian tissue in the central of ovarian cavity. Spermatogonia multiplicate and cavity tissue consist of testicular tissue. These gonad become hermaphrodite and then ditermine the sex of female and male. These results show the red sea bream is juvenile hermaphrodite and undif-ferentiated gonochoristic teleost. Male and female differentiation type of gonad is divided in undifferentiation stage, oogonia-like stage, ovary-like stage, ovary development stage, hermaphroditic testis stage, hermaphroditic ovary stage, and testis development stage. Undifferentiation stage is continued total lenth 18cm at 13 months after hatching. ovary-like stage is continued total length 11~18cm at 13 months after hatching. Ovary-like stage is continued total length 14~26cm at 10~14 months after hatching. Ovary development stage begins from total length 20cm, 14 months after hatching. At 20 months after hatching, 44 percent of total sampled individuals had ovary. Hermaphroditic ovary stage first begins total length 19~20 cm at 15 months after hatching, but it is not observed total length 28~29cm at 20months after hatching. Hermaphroditic testis stage first begins total length 21~22cm at 20months after hatching and is continued for 20months. Testis development stage first begins total length 20~21cm at 20 months after hatching, and is occupied 33 percent total length 28~29cm at 20 months. The beginning of sex differentiation more than 50 percent is from total length 16cm at 11 months after hatching. Sex determination begins total length 20cm, 14months after hatching in female and total length 20cm, 15 months after hatching in male. Sex determination more than 50 percent begins total length 23cm,, 17 months after hatching. Undifferentiated gonadal part of red sea bream consist gonad and fat body. As differentiation is going on and gonad is growing, fat body shrinks. This appearence is showed the same tendency in 3-year old red sea bream. 1.9mm larvae after hatching grow about 19mm larvae for 47 days. The relationship between the total length and body weight of larvae and juveniles in $BW=4.45{\times}10^{-6}TL^{3.4718}$ r=0.9820. Fishes in cage culture grow to maximum total length 28.4cm. The relationship between the total length and body weight of these fishes is $BW=2.36{\times}10^{-2}TL^{2.9180}$, r=0.9971. Undifferentiated gonadal part of red sea bream consist gonad and fat body. As differentiation is going on and gonad is growing, fat body shrinks.

• Development and Reproduction
• /
• v.11 no.3
• /
• pp.195-203
• /
• 2007

Sex determination and sex differentiation are influenced by genotype in many gonochoristic fish. Cytochrome P450 aromatase (CYP19) is the terminal enzyme in steridogenic pathway that converts androgens into estrogens. In this study, partial fragments of aromatase genes (ovarian aromatase, P450aromA and brain aromatase, P450aromB) were cloned and sequenced in Korean rockfish (Sebastes schlegeli), and gene specific primers were designed based on their sequences. Using these primers, aromatase gene expression during sex differentiation was investigated by RT-PCR. Expression of these aromatase genes were detected both in the head and body parts at 35 dab (days after birth). The number of fish that expressed the aromatase genes decreased at 52 dab, implying down-regulation of these genes. However, these genes were expressed at 59 dab in almost all fish studied here. The expression patterns of both genes are similar throughout the investigated period except for 45 dab where the expression of P450aromB was detected in more fish than that of P450aromA both in the head and body parts. Timing of sex differentiation in this species has been shown to be at around $50{\sim}65$ dab by histological analysis. However, the results from this study suggest that sex differentiation of rockfish may take place $1{\sim}2$ weeks earlier than the period proposed previously. The results also suggest that the mechanism of sex differentiation in viviparous fish may be similar to that in oviparous fish in terms of the importance of aromatase action during the critical period.