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.