Timing of a Single Daily Meal and Diel Variations of Serum Thyroxine, Triiodothyronine and Cortisol in Goldfish Carassius auratus
Two groups of goldfish were maintained on a 12L:12D photoperiod at 19°C and fed either at 0800 (light onset) or 1600 h daily. After 3 weeks, blood samples were taken at one of six times of day and the serum was analyzed for thyroxine, triiodothyronine, and cortisol by radioimmunoassay. Fish fed in the morning had significant diel variations in circulating titers of thyroxine and cortisol, those fed in the afternoon had significant variations of thyroxine and triiodothyronine. Meal feeding appeared to entrain, and phase shift, the cortisol rhythm but not the rhythms of thyroid hormones. These results are briefly discussed in light of the effects of timing the daily meal on weight gain in fish.
Richard E. Spieler and Teresa A. Noeske. 1981. Timing of a Single Daily Meal and Diel Variations of Serum Thyroxine, Triiodothyronine and Cortisol in Goldfish Carassius auratus .Life Sciences , (26) : 2939 -2944. https://nsuworks.nova.edu/occ_facarticles/196.