Lunar Age-Dependent Oscillations in Expression of the Genes for Kisspeptin, GnIH, and Their Receptors in the Grass Puffer during the Spawning Season.

Grass puffer is a semilunar-synchronized spawner: spawning occurs on beaches only for several days of spring tide around new moon (lunar age 0) and full moon (lunar age 15) every 2 weeks from spring to early summer. To investigate the role of kisspeptin and gonadotropin-inhibitory hormone (GnIH) in the semilunar-synchronized spawning, lunar age-dependent expression of the genes encoding kisspeptin (), kisspeptin receptor (), GnIH (), GnIH receptor (), gonadotropin-releasing hormone 1 (GnRH1) (), and three gonadotropin (GTH) subunits (, , ) was examined in the male grass puffer, which was kept in an aquarium under natural light condition in a lunar month during the spawning period. In the brain, both and showed lunar variations with a peak at lunar age 10, while both and showed semilunar variations with two peaks at lunar age 0 and 20. On the other hand, showed semilunar variation with two peaks at lunar age 0 and 15. In the pituitary, , , , and showed similar variations to those shown in the brain. The and mRNA levels showed semilunar variations with two peaks at lunar age 0 and 15. The present study shows lunar and semilunar oscillations of / and / expressions, respectively, with their peaks around spring tide in the brain and pituitary along with the semilunar expressions of and the pituitary GTH subunit genes. These results suggest that the lunar age-dependent expressions of the kisspeptin, GnIH, and their receptor genes may be primarily important in the control of the precisely timed semilunar spawning of the grass puffer.