Abstract
Effects of estradiol-17 β on the giant freshwater prawn were observed in case of the embryonic tolerance, growth, development, survival rate, yolk adsorption, eye appearance, and muscular compactness. The methods were designed in two steps; those were the tolerance and the growth. In the two hours after spawning, embryos were immersed in 0.5, 10, 50, 100, or 150 µg/ml estradiol-17β solution for two days, and the controls were treated with 15% artificial seawater. The tolerance was monitored in a separate experiment; they were immersed in 10, 50, 100, or 150 µg/ml estradiol-17β solutions showed that the mortality rate at 150 µg/ml estradiol-17β was 31.66%. The growth represented by yolk adsorption, hatching rate, and eye appearance. The results showed that the eyes appeared earlier than those of the controls. The survival rates were investigated in other experiments. The results showed that the highest survival rate was 48.16 %, observed in the 50 µg/ml estradiol-17β treatment. Therefore, estradiol might accelerate the growth as indicated by the number of days for eye appearance being the shorter period than in the control treatment. The eyes of the embryos treated with 50, 100, and 150 µg/ml estradiol-17β appeared on day 10, whereas those in the control were observed on day 16. Hatching rate was tending to high in 150 µg/ml estradiol-17β but those were not significant with the control. Yolk adsorption was found in treated embryo rather than those of the controls. The pattern of yolk cluster distribution was differing from the control. The muscle tissue was observed on day 20 after the histological process. The results showed that the bundle's muscle cells were more compactness and were larger, denser, and stronger with increasing concentrations of estradiol-17 β than that the controls. Therefore, estradiol-17 β should be applied to stimulate growth and might be introduced with the feed to the prawn industry and manufacturing.
Key words: estradiol-17β, embryonic development, muscles, giant freshwater prawn
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