In order to examine the effects of four different light spectra (white, red, green, and blue) on the oocyte maturation, the change of reproductive parameters, via brain-pituitary-gonad (BPG) axis in grass puffer, were investigated. After exposure four different light spectra for 7 weeks, the abundance of gonadotropin-releasing hormone (GnRH) mRNA which is a type of seabream (sbGnRH) and two different subunit of gonadotropin hormones mRNAs, follicle-stimulating hormone (fshβ) mRNA and luteinizing hormone (lhβ) mRNA, were analyzed in the brain and pituitary. Histological analysis showed that the mature oocyte ratio in the green spectrum was higher than other light spectra-exposed groups. Gonadosomatic index (GSI) and oocyte developmental stage were also investigated in the gonad based on histological observations. GSI value with the presence of yolk stage oocytes was significantly increased in the green spectrum-exposed group when compared to that of the other light-exposed groups (white, red, and blue) (p˂0.05). The abundances of sbGnRH mRNA and fshβ mRNA in the green spectrum-exposed group were also significant higher than those of the other light spectra-exposed groups (p˂0.05). These results indicate that the maturation of oocyte in grass puffer can be accelerated by exposure to the spectrum of green. To better understand the molecular mechanism for the maturation of oocyte in grass puffer, further study examining the relationship between oocyte development and its related genes is required.

In order to examine the effects of four different light spectra (i.e., white, red, green, blue) on the oocyte maturation in grass puffer, the change of reproductive parameters via brain-pituitary-gonad (BPG) axis were investigated in this study. After exposure to four different light spectra for 7 weeks, the abundance of gonadotropin-releasing hormone (GnRH) mRNA which is a type of seabream (sbGnRH) and two different of subunit of gonadotropin hormones mRNAs, follicle-stimulating hormone (fshβ) mRNA and luteinizing hormone (lhβ) mRNA, were analyzed in the brain and pituitary. Gonadosomatic index (GSI) and oocyte developmental stage were also investigated in the gonad based on anatomical- and histological observations. GSI value was significantly increased in the green spectrum-exposed group when compared to that of the other light-exposed groups (i.e., white, red, blue), with the presence of yolk stage oocytes (p˂0.05). The abundances of sbGnRHmRNA and fshβ mRNA in the green spectrum-exposed group were also significant higher than those of the other light spectra-exposed groups(p˂0.05). However, there was no significant difference between the abundances of lhβmRNA in all light spectra-exposed groups. These results indicate that the maturation of oocyte in grass puffercan be accelerated by exposure to the spectrum of green. The sbGnRHmRNA and fshβ mRNA may play an important reproductive parameters role in the initiation of maturation of oocyte. To better understand the molecular mechanism for the maturation of oocytein grass puffer, further study examining the relationship between oocyte development and its related genes (e.g., sbGnRHmRNA and fshβmRNA) is required.

In fish, light (photoperiod, intensity and spectra) is main regulator in many physiological actions including body growth. The present study was to investigate the effect of light spectra on the body growth in red spotted grouper Epinephelus akaara. Experiment performed from December, 2016 to March, 2017 and fish (n=200, body weight 6.9±0.1, total length 7.5±0.1) was reared under different light spectra (blue, green, red and white) for 15 week under 12 hour light and 12 hour dark photoperiod and natural water temperature (13.6~16.7℃). We examined the mRNA expression levels of growth hormone (GH) in the brain with pituitary and photoreceptors mRNA expression in the retina. Red spotted grouper of BW was no different in each for the four groups (light spectra of blue, green, red and white) to five week of rearing period, but BW of rearing blue light spectra group fish was significantly increased in ten week of rearing period. After that, in 15week of rearing period, BW of four group fish was no showed difference respectively. The total length (TL) of fish was no differed in four experimental groups under the experimental duration respectively. The gh mRNA was more highly expressed in rearing blue light spectra group fish than other experimental groups in 15 weeks. The short wavelength sensitive opsin (sws) mRNA was more increased in rearing blue light spectra group fish than other groups in 15 weeks. The middle wavelength sensitive opsin (mws) and rod opsin mRNA expression was no differed in four experimental groups under all experimental durations respectively. The long wavelength sensitive opsin (lws) mRNA expression was more increased in rearing red light spectra group fish than other groups in 15 weeks. Our present results suggest that somatic growth of red spotted grouper is induced under blue light condition under low water temperature duration. Also, these results are thought to be affected of the gh and sws mRNA expression blue wavelength. However, in this experiment we did not confirm the correlation between GH and photoreceptor. Therefore, further studies are needed to clarify the correlation of the light spectra and photoreceptor with body growth in red spotted grouper.

In fish, light (photoperiod, intensity and spectra) is main regulator in many physiological actions including growth. We investigate the effect of light spectra on the somatic growth and growth-related gene expression in the rearing tiger puffer. Fish was reared under different light spectra (blue, green and red) for 8 weeks. Fish body weight and total length were promoted when reared under green light condition than red light condition. Expression of somatostatins (ss1 and ss2) in brain were showed higher expression under red light condition than green light condition. The ss3 mRNA was observed only higher expression in blue light condition. Expression of growth hormone (gh) in pituitary was detected no different levels between experimental groups. However, the fish of green light condition group was showed more high weight gain and feed efficiency than other light condition groups. Our present results suggest that somatic growth of tiger puffer is induced under green light condition because of inhibiting ss mRNA expression in brain by effect of green wavelength.

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. 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 mucus-secreting goblet cell activity in order to develop a good management protocol and optimal rearing system for nursery stage of Epinephelus akaara. For each light spectrum, fish (11.5 ± 0.2 g in mean initial body weight, 9.0 ± 0.1 cm mean initial total length) were reared 16 weeks under a flow-through system and fed commercial pellet diets twice 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 and feed efficiency were observed in fish reared under the green light condition. Mucus-secreting goblet cell activity was significantly higher in the fish under green light condition than in the fish under the natural, red, and blue light conditions. Rearing of E. akaara under the green light condition had positive effects on fish growth performance and digestion. We recommend that the appropriate light spectrum for nursery stage of E. akaara is the green light condition from the perspective of growth performance and the synergistic effects of mucus-secreting goblet cells. However, longer light treatment periods are needed in future investigations to clarify the effects of light spectrum on each growing stage of E. akaara.

We investigated the change mRNA expression of GtHs subunits (FSHβ, LHβ) in the pituitary, androgen receptor (AR), estrogen receptor (ERα) in gonad and histological observation of gonads in longthooth grouper Epinephelus bruneus by treatment Femara, an aromatase inhibitor (AI). Longtooth grouper (body weight 408±43.1 g; one year) cultured in Future Aquaculture Research Center, NFRDI were used in the experiments. The experiment was conducted for 12 weeks from 21 August 2013. Fish received intramuscular injection of AI at 5 mg/g BW dose in three times every 3 weeks. Fish were sampled pituitary and gonads at 3, 6, 12 weeks post-injection (n=50). The mRNA levels of FSH-β, LH-β in pituitary and AR, ERα mRNA in gonad were evaluated using qRT-PCR and qPCR. The histological change of gonads observed on light microscope. The gonads of control group contained most perinucleolus oocyte. At 3 to 6 weeks post-injection, the gonads of AI-treated group contained a few degenerated oocytes, spermatogonia and spermatocytes. At 12 weeks post-injection, gonads contained spermatids undergoing spermatogenesis. From 6 to 12 weeks post-injection, the expression level of GtHs subunits mRNA in pituitary was significantly higher than control group. The expression level of AR mRNA in gonad was higher than control group from 3 to 12 weeks post-injection. The expression level of ERα mRNA in gonad was lower than control group from 6 to 12 weeks post-injection. These results suggest that immature longtooth grouper with AI treatment induced masculinization via change of GtH subunits in pituitary, AR and ERα mRNA in gonad.

To effects of sex maturation in olive flounder by regulating long photoperiod, gonadal development and GTH mRNA expression in the pituitary were investigated. Photoperiod was treated natural photoperiod and long photoperiod (15L:9D) conditions from September 2011 to March 2012. The results showed that natural photoperiodic group showed a higher gonadosomatic index (GSI) than long photoperiodic group during the spawning season (March 2012). The histological analysis of ovarian tissue showed that natural photoperiod group of ovaries contained vitellogenic oocytes, but long photoperiod group of ovaries mainly contained perinucleolus staged oocyte and oil-drop staged oocytes. The FSH mRNA of olive flounder, under natural photoperiod group, showed a significantly higher expression but no significant difference under long photoperiod group. The LHβ mRNA showed a significantly higher expression only under natural photoperiod group. These results may suggest that long photoperiodic information regulates secretion of pituitary FSH and LH and maintain early growing stage of gonadal development in this species.