EFFECT OF THE LENGTH OF THE DAILY PHOTOPERIOD ON THYROID ACTIVITY IN THE FEMALE JAPANESE QUAIL (COTURNIX COTURNIX JAPONICA)

Abstract

In birds the interaction between day-length and the activity of the thyroid gland is complex: pituitary thyrotrophs are stimulated in the male quail by exposure to a long daily photoperiod (Tixier-Vidal, Follett & Farner, 1967) but the uptake of radioactive iodine by the thyroid is depressed in male ducks (Tixier-Vidal & Assenmacher, 1965) and male quail (Baylé & Assenmacher, 1967). This depression of thyroidal activity is thought to arise from the gonadal development induced by long days and is possibly mediated by gonadal steroids. Thus castration intensely stimulates pituitary thyrotrophs in the duck (Tixier-Vidal & Assenmacher, 1965) and quail (Tixier-Vidal et al. 1967) and also increases thyroidal uptake of radioactive iodine (Tixier-Vidal & Assenmacher, 1965). Since the two effects of light on pituitary thyrotrophs and iodine uptake by the thyroid were somewhat contradictory the matter was investigated further in the female Japanese quail (Coturnix coturnix japonica) subjected to long daily