Characteristics and functional significance of daily cycles in serum gonadotropin hormone levels in the goldfish.
Goldfish were subjected to 12L:12D/12 degrees C, 16L:8D/20 degrees C, or to an outdoor pond regime for various lengths of time at several times of year. Serum gonadotropin hormone (GTH) levels were determined through 24-h periods and ovaries were examined histologically. Low and uniform serum GTH levels were found throughout the day in fish under 12L:12D/12 degrees C for 32 days in November; significant fluctuations were found under this regime after 32 days in March. In fish held under 16L:8D/20 degrees C, a peak in serum GTH levels was detected after 7 days in November and after 13 days in March. GTH levels were high and uniform throughout the day after 32 days in November and March. Patterns of daily cycles in serum GTH levels of fish kept in an outdoor pond were similar to the patterns detected in the laboratory under similar conditions of photoperiod and temperature. Fluctuating serum GTH levels were correlated with greater oocyte growth than constant low levels. Constant high serum GTH levels were correlated with oocyte atresia.
D000818:Animals; D002940:Circadian Rhythm; D003530:Cyprinidae / Q000097:blood*; D005260:Female; D006054:Goldfish / Q000097:blood* / Q000502:physiology; D006065:Gonadotropins, Pituitary / Q000097:blood*; D008027:Light; D008297:Male; D010053:Ovary / Q000033:anatomy & histology; D011863:Radioimmunoassay; D013696:Temperature
D006065:Gonadotropins, Pituitary