Abstract
The purpose of this study was to examine the effects of oral-administered sex hormone for hybrid sturgeon, bester juvenile. The bester juveniles (2 months after hatching) were received a diet containing various doses of <TEX>$17\alpha$</TEX>-methyltestosterone (MT) or estradiol-<TEX>$17\beta$</TEX> (<TEX>$E_2$</TEX>) for 6 months. Somatic growth of bester sturgeon juvenile did not show significant differences between experimental and control groups (27.9-30.5 cm; 125.1-161.7 g), although survival percentages showed a decreasing tendency in MT-treated animals. By histological examination, germ cells were recorded as smooth type in MT-treated fish and uneven type of germinal epithelium in <TEX>$E_2$</TEX>-treated animals. Their sex ratios were 5:4:1 (male: female: undifferentiation) in control and low dose of MT-treated fish (1 mg/kg), and 9:1:0 in fish treated with high dose of MT (10 mg/kg), whereas the ratios were reversed by both low and high doses of <TEX>$E_2$</TEX> treatment, recorded as 2:8:0. Gonadal areas were not significantly differed in all trials (424,600.4 - 1,039,656.3 <TEX>${\mu}m^2$</TEX>). Total number of germ cells, number of germ cells per gonadal areas and number of germ cells per area were significantly higher to 144.7-148.7 cells/section, 374.0-408.5 <TEX>$cells/mm^2$</TEX> and 1,599.5-1,670.9 <TEX>$cells/mm^2$</TEX> in <TEX>$E_2$</TEX> treatment than those of others (30.4-63.9 cells/section, 148.4-226.9 <TEX>$cells/mm^2$</TEX> and 850.0-1,050.6 <TEX>$cells/mm^2$</TEX>), respectively. And somatic growth according to their gender was not significantly differed between male and female.
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