Vol. 39 No. 1, 2000
Sex Differences in the Responses of Serum Calcium Concentrations to Temperature and Estrogen in Tilapia, Oreochromis mossambicus
Ching-Lin Tsai* and Li-Hsueh Wang
Department of Marine Resources, National Sun Yat-sen University, Kaohsiung, Taiwan 804
Ching-Lin Tsai and Li-Hsueh Wang (2000) Sex differences in the responses of serum calcium concentrations to temperature and estrogen in tilapia, Oreochromis mossambicus,
were investigated. Prespawning males and females were kept at 26, 29,
and 32°C aquatic temperatures for 21 d. The serum calcium levels
increased by elevated temperature in females but were not altered in
males. Females showed higher serum calcium levels than males at the 26,
29, and 32°C exposure groups, respectively. On the other hand, males
and females were gonadectomized and treated with different dosages of
17β-estradiol for 21 d. Serum calcium levels significantly decreased
after gonadectomy in females but were not altered in males. There was
no difference in serum calcium levels between gonadectomized males and
females. Treatment with 17β-estradiol at 50 or 100 mg/kg diet
significantly increased serum calcium levels dose-dependently in both
gonadectomized males and females. The hypercalcemic effect of
17β-estradiol was greater in castrated males. These results suggest
that the estrogen induced calcium regulatory system is temperature
dependent in females and not in males. On the other hand, estrogen
induced elevation of blood calcium level is more pronounced in males
than in females.
Key words: Estradiol, Serum calcium, Sex difference, Temperature, Tilapia.
*Correspondence: Tel: 886-7-5255032. Fax: 886-7-5255020.