STUDY OF 17β-ESTRADIOL HORMONE CONCENTRATION AND HISTOLOGY OF GONAD TISSUE IN RELATION TO FEMINIZATION AND GROWTH RATE OF PASIFIC WHITE SHRIMP (LITOPENAEUS VANNAMEI, BOONE 1931) POSTLARVAE
This study was conducted to determine the effect of different concentration of estrogen hormone, 17β-estradiol (E2) on feminization for the production of all female and growth rate of Pasific white shrimp (Litopenaeus vannamei) postlarvae. L. vannamei PL1 were randomly stocked at a density of 10 ind.L-1 into a 10L of seawater for each experimental flask with three replicates each. PL1 was immersed in seawater containing 0.2, 0.4 and 0.6 mg/L estrogen hormone (E2) for 4 hours. The experiment was continued for 60 days. At termination of experiment, the specimens in each treatment group were individually weighed and measured for their wet body weight (BW) and total length (TL) to estimate the weight gain, length gain and the specific growth rate (SGR). The mean sex values of female gained from control till the highest E2 hormone concentration of 0, 0.2, 0.4 and 0.6 mg.L-1 were 38.89%, 52.22%, 63.33% and 78.89% respectively. The immersion dose treatment in the E2 hormone also had a significant effect (P<0.05) on the weight and length growth of white shrimp post-larvae compared to the control. The weight gain and length gain were 126824% and 900% for control, 135748% and 954% for 0.2 mg.L-1 concentration, 149662% and 961% for 0.4 mg.L-1 concentration and 151029% and 964% for 0.6 mg.L-1. The mean SGR BW and SGR TL for control till the highest E2 hormone concentration of 0, 0.2, 0.4 and 0.6 mg.L-1 were 11.91 and 3.84, 12.02 and 3.93, 12.18 and 3.94 and 12.20 and 3.94 respectively. This difference is thought to be caused by differences in weight and length between male and female individuals. The increase in the percentage of female individuals and the growth rate of Litopenaeus vannamei post-larvae in various treatments compared to controls in this study was influenced by differences in the concentration or dose of the E2 hormone given. This is related to the ratio of the amount of the E2 hormone that is absorbed into the body of the post-larvae osmotically. The higher concentration of the E2 hormone used in post-larva immersion caused higher amount of E2 hormone absorbed into the post-larva's body. The E2 hormone concentration of 0.6 mg.L-1 turned out to be the highest level of absorption into the post-larval body, namely an average of 105 pg.mL-1 and it is what causes the percentage of female sex and the growth rate of vaname shrimp post-larval to be the highest compared to other treatments. Histological tests on vaname shrimp gonad tissue samples resulting from the study did not reveal any hermaphrodite individuals.
17β-Estradiol, Feminization, Litopenaeus Vannamei, Postlarvae, Growth Performance, Gonad Tissue.