The role of pineal and eyes in the photoperiodic effect on the gonad of the medaka, Oryzias latipes.
Studies on gonadal development in the female medaka, Oryzias latipes, intact, blinded or blinded-pinealectomized, maintained on different lighting schedules, i.e. LD14:10 and LD 10:14 and under natural daylight conditions, revealed that: 1)blinded fish were capable of responding to annual photoperiodic shifts with alterations of gonadal development, if the pineal was left intact; 2)the mean gonosomatic index(GSI) was higher in blinded fish than in intact fish, during a period from October through April, under LD 14:10, LD 10:14 and the natural daylight conditions; 3)when reared under the natural daylight conditions, the mean GSI in blinded fish was approximately half of that in intact ones in May and June, although the values were significantly larger than those in fish examined during all the other seasons; and 4)in December, the mean GSI was larger in blinded-pinealectomized fish than in intact and blinded ones. These findings seem to indicate that, during the breeding season, the gonadal growth in the medaka is stimulated by the pineal blocking the inhibitory mechanism against the hypothalamo-hypophyseal gonadotropic system, whereas during non-breeding seasons, the gonadal involution is induced by an anti-gonadal factor released by the pineal. It is likely that the effects of photoperiods are exerted on the pineal through the eyes.
D000818:Animals; D001766:Blindness; D001827:Body Height; D001835:Body Weight; D005260:Female; D005399:Fishes / Q000502:physiology*; D008027:Light; D009799:Ocular Physiological Phenomena; D009929:Organ Size; D010053:Ovary / Q000033:anatomy & histology / Q000502:physiology*; D010507:Periodicity; D010870:Pineal Gland / Q000502:physiology* / Q000601:surgery