Avaliação do citrato de tamoxifeno e temperatura na inversão sexual da tilápia do Nilo (Oreochromis niloticus).
Aquaculture in Brazil has been improving and finding new techniques to improve the quality of fish produced, one of the main problems is the use of steroids in sex inversion of tilapia, despite being a widespread technique and practiced in various regions of the world is increasing concern to environmental liabilities generated by the use of 17 α-methyltestosterone. In this context, this study aims to evaluate the overall use of non steroids in sex inversion of Nile tilapia. The first experiment was conducted to evaluate the influence of citrate tamoxifen on sex inversion of Nile tilapia larvae from two days of life, they were divided into an experimental design of five treatments and three replicates, and fed diets with different amounts of citrate tamoxifen: 0, 25, 50, 75 and 100 mg kg-1 of feed. After 28 days of treatment, the larvae remaining in each treatment were counted and transferred to water tanks of 500 liters which were fed a diet containing 28% crude protein for 60 days. After this period the fry were sexed by the "squash" method. The survival 75.5 ± 5.74, 73 ± 4.76, 66 ± 11.19, 76.5 ± 4.12, 75 ± 3.46 and average percentage of male individuals 62.5 ± 5, 70 ± 8.1, 60 ± 8.2, 70 ± 0.0, 62.5 ± 9.5 for treatments 0, 25, 50, 75 and 100 mg of citrate tamoxifen kg-1 diet, respectively, showed no statistically significant differences. The number of gonads in each subject experienced a significant reduction in the treatments with 75 and 100 mg of citrate tamoxifen (89.3 and 79.3 ± 0.527 ± 0.378) when compared with treatments 0, 25 and 50 mg of citrate tamoxifen (98, 9 ± 1.0, 97.6 ± 1.0 and 94.5 ± 1.0, respectively), the histological structure of female gonads did not differ and ovaries in all treatments showed well-defined and oocytes at various stages of maturation. The second experiment evaluated the effects of temperature 28, 30, 32 and 34°C and control (28ºC + ration plus 60 mg of 17 α-methyltestosterone) in sexual inversion, survival and presence of deformities in Nile tilapia. The results showed a statistical difference between the proportion of males, with a temperature of 32 and 34°C and control (91 ± 0.71; 96 ± 0.59 and 98.33 ± 1.0%, respectively) showed better results than those obtained for 28 and 30 degrees treatments (71 and 82 ± 0.29 ± 0.33%). Survival: 90.49 ± 2.32, 88.20 ± 2.04, 85.43 ± 1.58, 82.16 ± 1.63 and 90.74 ± 2.28% for temperatures 28, 30, 32 and 34°C, respectively, showed no statistical differences, but there were differences in survival between the control and treatments 32 and 34°C. In the analysis of radiographs was not possible to observe the presence of morphological changes in fish subjected to different treatments. With this experiment it was concluded that temperatures of 32 and 34°C larvae were able to genetically masculinizing females, and that there was no increase in mortality and in deformities presence that can be attributed to treatment. This technique is an alternative to the use of steroid hormones. The third experiment was conducted in order to describe gonads of Nile tilapia fingerlings (Supreme) with 75 days of age, using as a tool cytological techniques, structural and ultrastructural. Cytological technique gonads were stained with carmine acetate pressed between slide and coverslip and observed under light microscopy. To structural prepare gonads, after processing, were cut in microtome at thickness of 5 mm, stained with hematoxylin-eosin and observed under light microscopy. At the ultrastructural method, gonads were photo documented in a scanning electron microscope FEI QUANTA 200. The structural and cytological preparations allowed the visualization of the ovaries of oocytes, cell boundaries, nuclei and nucleoli associated. In males the cytologic preparations did not allow a clear identification of the structures, but in preparing structural testicular sperm was possible to visualize cysts, Sertoli cells and the beginning of the formation of seminiferous tubules. The scanning electron microscopy, used to visualize surface allowed, after the fracture of the gonads, to observe internal structure, such as spermatogonia, oocytes and collagen fibers. The results showed that all three techniques were efficient in distinguishing the sex of the individual, allowing observation and comparison of the structures present in the gonads.
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| Format: | Thesis/Dissertation biblioteca |
| Language: | Portuguese |
| Published: |
Universidade Estadual de Maringá. Centro de Ciências Agrárias. Programa de Pós-Graduação em Zootecnia
2011
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| Subjects: | Sexual inversion, Reproduction, Temperature, Tamoxifen Citrate, Brazil, Temperatura, Citrato de tamoxifeno, Brasil, Avaliação, Tilápia do Nilo, Inversão sexual, Reprodução, Oreochromis niloticus, Nile tilapia, Evaluation, |
| Online Access: | http://hdl.handle.net/1834/9840 |
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