title: Entrainment of daily serum gonadotropin cycles in the goldfish to photoperiod, feeding, and daily thermocycles.
abstract: Female fish were kept under 16L:8D/20 degrees C in November and April and the onset of light and/or feeding times were shifted by several hours in the experimental groups. Photoperiod and feeding entrained significant fluctuations in serum gonadotropin hormone (GTH) levels when the onset of light and the first daily feeding were 4 hr apart, but not when they were 10 hr apart. Fish were subjected to 16L:8D for 14-16 days in February, and to either a constant warm (20 degrees C) or a diurnal sinusoidal (12-20 degrees C) temperature regime, the warmth being imposed during photophase or scotophase. While relatively high, uniform serum GTH levels were found throughout the 24-hr period in fish subjected to constant warmth, warm temperature during the day promoted fluctuations in serum GTH levels, and warmth during night resulted in relatively low, uniform serum GTH levels.
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D003530:Cyprinidae / Q000097:blood*; D003624:Darkness; D004435:Eating; D005260:Female; D006054:Goldfish / Q000097:blood*; D006062:Gonadotropins / Q000097:blood*; D008027:Light; D012621:Seasons
chemical_list: D006062:Gonadotropins