Effect of long-afterglow phosphorescent pigment on reproductive parameters and ovarian maturation in the yellowtail damselfish, Chrysiptera parasema

Photoperiod is considered the most important factor that entrains animal rhythms, including the reproductive cycle. The present study tested differences in sex maturation and sex steroid hormones of yellowtail damselfish (Chrysiptera parasema) exposed to a white fluorescent bulb (12L:12D and 14L:10D) or long-afterglow phosphorescent pigment (LumiNova sheet) for 4 months. At the end of the experiment, in the phosphorescent group, mRNA expressions of gonadotropin hormones [(GTHs, including gonadotropin (GTH) α and luteinizing hormone (LH) β)], estrogen receptor (ER), and vitellogenin were significantly higher than in the photoperiod groups (12L:12D and 14L:10D), and these results are consistent with those of Western blotting for protein expression. Furthermore, in the phosphorescent group, plasma FSH, LH, and estradiol-17β (E2) levels were significantly higher than in the photoperiod groups. However, plasma melatonin levels were significantly lower than in the photoperiod groups. Because LumiNova sheets continue to emit green light (520 nm) for approximately 2 h after sunset, the extended light conditions probably contributed to reproductive ability in the experimental fish. In conclusion, long-afterglow phosphorescent pigment can be used for energy-efficient aquaculture to regulate the reproduction of fish, although its effect needs to be evaluated in other species.