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Effects Of Exogenous Hormone And Temperature On Sex Differentiation Of Large Yellow Croaker Larimichthys Crocea

Posted on:2013-09-15Degree:MasterType:Thesis
Country:ChinaCandidate:J YangFull Text:PDF
GTID:2283330461471278Subject:Aquaculture
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In this paper, effects of methyl testosterone, aromatase inhibitor and rising temperature on sex differentiation of larvae and juveniles of large yellow croaker Larimichthys crocea were preliminarily studied. After treatments of methyl testosterone, Letrozole and water temperature, sex of each individual was determined by observing its gonadal tissue slices and then sex ratio of male was counted, respectively.1. Larvae and juveniles of large yellow croaker were fed with feed soaking in different concentrations of methyl testosterone and three treatment times of 1, 2 and 3-months were set up. Results showed that short-time or low methyl testosterone concentration treatment could improve growth of large yellow croaker, but long-time or high methyl testosterone concentration treatment could inhibit growth of large yellow croaker. Besides, influences of treatment time to growth of large yellow croaker were larger than that of methyl testosterone concentration. Male sex ratio of each test group after 1 or 2 months methyl testosterone treatment was at 30.95%~67.65%. There was no significant difference compared to the control group. Male sex ratio of each test group after 3 months methyl testosterone treatment was at 80.00%~95.65%. It was significantly higher than that of the control group, and differences between different concentration groups were not significant. Influences of treatment time to sex differentiation of large yellow croaker were larger than that of methyl testosterone concentration.2. Larvae and juveniles of large yellow croaker were fed with feed soaking in different concentrations of Letrozole and three treatment times of 1, 2 and 3-months were set up. Results showed that effects of Letrozole on growth of large yellow croaker were not significant. Body length and body weight of larvae and juveniles of large yellow croaker in each test group after different time and concentration treatment basically had no difference with that of the control group. Male sex ratios of low concentration test groups were at 40.00%~65.00%. But as treatment time prolonging, male sex ratios of high concentration test groups were up to over 70.00%.3. Larvae and juveniles of large yellow croaker were bred at water temperature(26±0.5) ℃,(28±0.5) ℃ and(30±0.5) ℃, respectively. The control group was bred at(22±1) ℃. Results showed that high temperature was beneficial to growth of larger yellow croaker, but there was no significant difference between the three groups. The culture situation in group raised at 28 ℃ was slightly better than that of groups raised at 26 and 30 ℃. Male sex ratio of the high temperature group in which treatment started when juveniles gained 2.5cm in body length was over 75.00% and was higher than that of the control group whose male sex ratio was 65.45%. There is no remarkable difference between the control group Male sex ratios of the test groups in which treatment started when juveniles gained 1.5 cm and 3.5 cm in body length was approximately 60.00%.
Keywords/Search Tags:Large yellow croaker, Methyl Testosterone, Letrozole, Sex differentiation, Temperature
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