• Development and Reproduction
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• v.20 no.3
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• pp.267-274
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• 2016

Cichlid fish species exhibit characteristic sexual behaviors according to not only reproductive stages but also social status. In a reproductive season, Astatotilapia burtoni males compete for females and a small number of dominant winners finally obtain the chance of spermiation. In addition to the characteristic behaviors, the dominant males have relatively bigger gonadotropin-releasing hormone 1 (GnRH1) neurons in the preoptic area (POA) of brain compared to those of subordinate males. Although the stimulatory effect of GnRH1 in vertebrate reproduction is well established, little is known about the triggering signal pathway to control GnRH1 neurons and GnRH1-mediated sexual behavior. In the present study, we evaluated the potential effect of TOR inhibitor rapamycin in relation to the cichlid male behaviors and GnRH1 neuron. After 14 h and 26 h of intraventricular injection of rapamycin, behavior patterns of chasing and courtship display did not show significant changes between rapamycin- and DMSO-injected males. Behaviors of spawning site entry increased in rapamycin-injected fish at 26 h post-injection than at 14 h post-injection significantly (P<0.05). Meanwhile, there was a tendency that GnRH1 neurons' soma size in the POA shrank by rapamycin injection, whereas the testes did not show notable changes. Taken together, these results suggest the possible role of TOR signal on GnRH1-mediated sexual behavior in cichlid dominant males, although further biological characterization of the TOR signaling pathway will be required to clarify this matter.

• Development and Reproduction
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• v.17 no.2
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• pp.79-85
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• 2013

To understand the sex reversal characteristics in the longtooth grouper (Epinephelus bruneus), this study examined the sex reversal and artificial masculinization of wild caught E. bruneus reared in indoor rearing tank after a 17${\alpha}$-methyltestosterone injection. To domesticate a broodstock, 64 wild caught E. bruneus, between 47.0 to 110.0 cm in total length and from 1.5 to 21.4 kg in body weight, were reared in indoor rearing tank (4.0 to 5.0 m wide, and 2.5 to 3.0 m depth) for four years. Seven specimens showed sex reversal from female to male during indoor rearing condition, whose total length and body weights were from 63.0 to 99.0 cm and from 4.4 to 13.2 kg, respectively. After inducing artificial masculinization in 14 female E. bruneus with a 17${\alpha}$-methyltestosterone (2.0 mg/kg BW) implants for 3 years, spermiation occurred in 9 specimens (total length: 54.0 to 68.0 cm, body weight: 2.3 to 4.3 kg). Among the female to male sex reversals, two specimens returned back to being female, whose body weights were 2.8 kg (initially 2.6 kg) and 2.7 kg (initially 2.3 kg). Therefore, this study suggested that E. bruneus (> 3.0 kg) was more effective in masculinizing by 17${\alpha}$-methyltestosterone implants.

• The Korean Journal of Zoology
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• v.38 no.3
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• pp.395-404
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• 1995

In order to study the process of spermiogenesis of the korean striped field mouse Apodemus agrorfus coreae, the cell differentiation of seminiferous epithelium and morphological features of mature sperm in cauda epididymis was examined and the results are as follows: Spermiogenesis was divided, according to the features of cell structure; Golgi, cap, acrosome and spermiation phases were further subdivided into two steps of early and late phases respectively, and maturation phase has only one step. Hence, the spermiogenesis consists of nine phases. in the changes of the chromatin in nucleus, the chromatin granules began to be condensed in the cap phase and the condensation proceeded to form a globular of nucleus at the acrsome phase. Finally, the chromatin regularization was completed and perfect nucleus of sperm was formed at the maturation phase. Sperm head had the falciform, and the outer dence fibers of middle piece were arranged in a horseshoe fashion. The outer dence fiber number 1, 5, 6 and 9 was larger than other fiber number 2, 3, 4, 7, 8.

• Journal of Aquaculture
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• v.22 no.1
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• pp.5-10
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• 2009

Spermatogenesis in male yellow croaker Larimichthys polyactis was histologically investigated by sampling testicular tissue from $2{\sim}3$ years old wild fishes captured from the coast of Mok-Po, South Korea. Spermatogenesis was characterized histologically, and staged according to the most advanced type of germ cell present. Annual reproductive cycle was classified into the following successive 4 stages: spermatogonia from August to September (rest stage), spermatogonia and spermatocytes from October to December (growth stage), spermatogonia, spermatocytes and spermatids from January to February (maturation stage), spermatogonia, spermatocytes, spermatids and spermatozoa from March to May (spermiation stage IV), and regressing testis from June to July (degeneration stage).

• Korean Journal of Ichthyology
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• v.18 no.4
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• pp.311-318
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• 2006

Ultrastructure of germ cells, the cyst epithelial cells and interstitial cells during spermatogenesis of the stone flounder, Kareius bicoloratus (Pleuronectidae) sampled on the west coast of Korea were investigated by electron microscopic observations. In the primary spermatocyte, the synaptonemal complexes appear in the zygotene stage of the prophase during maturation division. In the growing testis, especially, the interstitial cells (Leydig cells) appear near the primary, secondary spermatocytes and spermatids. Well-developed interstitial cells (steroid hormone secreting cells) which are located in the interlobular space in growing testis have three morphological characteristics of a vesicular nucleus, mitochondria with tubular cristae and smooth endoplasmic reticulum. During spermatogenesis, the primary and secondary spermatocytes attach to the cyst epithelial cell (Sertoli cell) having an elongated ovoid or triangular nucleus and several mitochondria in the cytoplasm. In the growing testis, lipid droplets, the mitochondrial rosettes and glycogen particles appear in the cytoplasm of the cyst epithelial cells near the secondary spermatocytes and spermatids. Particularly, the mitochondria, endoplasmic reticulum, little lipid droplets and the large amount of glycogen particles are present in the cytoplasm of the cyst epithelial cell in the late growing testis. In the late stage of spermiogenesis, the proximal centriole is joined to the nuclear envelope, the distal centriole forms the basal body of the flagellum and gives rise to the axial filament of the flagellum. No acrosome of the sperm is formed as seen in other teleost fish. The head of the spermatozoon is approximately $3{\mu}m$ in length and its tail is about $30{\mu}m$ in length. The axoneme of the tail flagellum of the spermatozoon consists of nine outer doublet microtubules at the periphery and two centrial singlet microtubules at the center. The spermatozoon of this species has two axonemal lateral fins. Especially, the cyst epithelial cells which located near groups of gametes in the various stages, show three functions: nutrition, phagocytosis and steroidogenesis. Especially, the nuclei of cyst epithelial cells in the recovery stage of the testicular developmental stages appear to be irregular in shape after spermiation. Of three functions of the cyst epithelial cell, several characteristics of phagocytosis are showed in the cytoplasm of the cyst epithelial cells in the recovery stage of the testicular developmental stages. At this stage, therefore, it is assumed that the cyst epithelial cells are involved in degeneration and resorption of undischarged germ cells after spermiation.

• Development and Reproduction
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• v.9 no.1
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• pp.15-22
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• 2005

The objective of the present study was to investigate changes of sex steroid(testosterone: T and $estradiol-17{\beta}:\;E_2$), cortisol levels and gonadal development following $T_3$ treatment to protandrous black porgy, Acanthopagrus schlegeli. Exogenous $T_3$ was found to significantly stimulate the increase of T levels in plasma of black porgy after 60 days of treatment. However no effects of $T_3$ on $E_2$ levels and oocyte size were found. $T_3$ treatment resulted in stimulated spermatogenesis and testicular development in gonad and prolonged spermiation. Also, the levels of cortisol were significantly increased in the fish treated with $T_3$ as compared to control fish at 60 days. The results showed that exogenous $T_3$ had direct effect on the release of T and cortisol, thus $T_3$ seems to play, either directly or indirectly, an important role in the testis development of functional male black porgy.

• Applied Microscopy
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• v.37 no.3
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• pp.185-198
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• 2007

Spermiogenesis in Japanese white-toothed shrew. Crocidura dsinezumi was investigated by transmission electron microscope. Spermiogenesis was divided into 12 phases 14 steps, based on the morphological features of the nucleus and change of organelles in cytoplasm. The nucleus of spermatids in Golgi (step $1{\sim}2$) phase were spherical; however, they were changed into oval in the cap (step $3{\sim}6$) phase. Flagellum appeared in the middle of acrosomal phase; on the other hand, slender and long spermatid head was formed in maturation phase. The head of spermatids faced the lumen in step 1 to step 6 (from Golgi to cap phase), but, in step 7 to step 14 (from acrosomal to spermiation phase), it turned its head to the basal lamina of the seminiferous epithelium. The nucleus and acrosome were elongated maximally in step 10. The condensation of chromatin started in late acrosomal (step 10) phase, and it was completely finished and homogenized in the middle of maturation (step 12) phase. Multivesicular body appeared near the acrosomal vacuole during the middle cap (step 5) phase, and a large number of them were observed near the Golgi apparatus in the late cap (step 6) phase. Considering all the results, the spermiogenesis might be useful information to analyse the differentiation of spermatogenic fells.

• The Korean Journal of Zoology
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• v.38 no.3
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• pp.405-416
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• 1995

The testis and the epididymis of sexually mature male bats were examined to investigate the process of spermiogenesis of Korean long-fingered bat (Miniopterus schreifersi fulignosus) using electron microscope. The ultrastructural findings were analysed on the basis of Lee's method (1992). Especially, we focused on the acrosome formation. The results are as follows: The spermiogenesis of the Korean long-fingered bat can be divided into ten phases on the basis of ultrastructural differentiation; three "Golgi" phases of early, mid and late stages, two "cap" and two "acrosome" phases respectively composed of early and late phases, one "maturation phase and two "spermiation" phases of early and late phases. The axoneme of sperm in the cauda epididymis is composed of nine outer dense fiber and a central singlet. The number 1, 5, 6, and 9 outer dense fibers are larger than others. In the Golgi phases, small vesicles are separated from Golgi vesicles and then appear to fuse into a large vesicle, and finally it contacd with the outerside of the nucleus. It suggests that proacrosomal material could be made in the cytoplasm before the Golgi vesicle formation and then it could be transferred into the Golgi vesicle and condensed more and more, and finally form acrosome, just as Lee;s suggestion (1992).m acrosome, just as Lee;s suggestion (1992).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.5
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• pp.624-628
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• 1999

Annual plasma levels of vitellogenin and sex steroids were investigated in relation to the gonadal development for understanding the endocrine control of reproduction in spotted flounder, Verasper variegatus. The plasma vitellogenin level was highest, 6.36 mg/ml, in November when vitellogenesis was most active. The level, thereafter, decreased to 3.81 mg/ml in December with the initiation of spawning. On the other hand, estradiol-17 $\beta$ was highest, 2.7 ng/ml, in December, and rapidly decreased in January when spawning occurred. The decreased level of estradiol-17$\beta$, around 0.2 ng/ml, remained unchanged until May. The profiles of plasma testosterone were similar to those of estradiol-17$\beta$ in the fish, The plasma 17 $\alpha$-hydroxyprogesterone level was relatively low throughout the spawning period, but increased slightly with the initiation of ovarian development, In males, the plasma testosterone and 11-ketotestosterone were highest in December when spermiation actively proceeded, but rapidly decreased during the spawning period (January).

• Journal of Aquaculture
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• v.20 no.4
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• pp.219-225
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• 2007

This study investigated the correlationship between artificial maturation season and reproduction coefficient of cultured eel Anguilla japonica from May (spring) to next January (winter). The brood stock, female eels ($400{\sim}600\;g$) were artificially matured by weekly intramuscular injections of salmon pituitary extracts (SPE, 20 mg/fish) to induce a completion of vitellogenesis. After completion of vitellogenesis, final oocyte maturation and ovulation was induced by injection of $17{\alpha}$, $20{\beta}-dihydroxyprogesterone$ (DHP) at about $2\;{\mu}g/g$ body weight. Most fish ovulated $15{\sim}18\;h$ following the DHP injection. The ovulated fish were induced to natural spawning or artificial fertilization by the dry method. Males ($200{\sim}350\;g$) were received weekly intramuscular injections of human chorionic gonadotropin (HCG) at a dosage of 1 IU/g body weight to induce testicular maturation and spermiation. Seasonal reproduction coefficient which includes the rate of ovulation, buoyancy, fertilization and hatching of eggs in the artificially matured eel during spring to summer ($May{\sim}July$) were significantly higher than the other season, while there were no significant difference among spring and summer (P<0.05). Furthermore, the number of eggs spawned and larvae hatched in the artificially maturated eel during spring to summer ($May{\sim}July$) were significantly higher than the other season, while there were no significant difference in spring and summer (P<0.05). These results indicate that artificial maturation by hormone treatment of A. japonica was successful only during spring to summer, which is the maturation period in the wild stock in nature. Consequently, it is possible to determine the period of artificially induced sexual maturity by the reproduction coefficient which includes the rate of ovulation, buoyancy, fertilization and hatching of eggs in the cultured eel A. japonica.