Effects of double transgenics for the somatotrophic axis on the growth and reproduction of zebrafish (Danio rerio)
Aquaculture is playing an important role in meeting the growing demand for fish worldwide. Currently, there is a beneficial interaction between aquaculture and biotechnology that favors the optimization of production through the application of biotechnological tools. Transgenesis is one of the most promising tools, where growth hormone (GH) has been the most important target in the search for genetically improved fish strains. However, it is established that the excess of GH causes a series of adverse effects due to its pleiotropic action. In this sense, the objective of this thesis was to evaluate the effect of double transgenics for the somatotrophic axis on the growth and reproduction of zebrafish (Danio rerio). Thus,the first work reports the production of a double-transgenic (GH / GHR) by crossing the F0104 strain (which overexpresses GH) with the Myo-GHR strain (which overexpresses the growth hormone receptor gene in a muscle-specific manner) . In the second study, the effect of double transgenics on skeletal muscle growth and structure was evaluated. The double-transgenic showed a growth comparable to the F0104 strain, although with a lower condition factor. Additionally, there was a decrease in the expression of a gene related to intracellular signaling in parallel with a strong decrease in the amount of thick muscle fibers. The third work aimed to evaluate the reproductive parameters of double-transgenic zebrafish males.The results showed a significant improvement in almost all the parameters analyzed, showing a reduction in the negative effects of GH on reproductive function. In conclusion, it is clear that the double-transgenic is an interesting study model that can generate new knowledge about the effects of GH in several biological and physiological aspects. It is necessary to note that the use of this hormone must respect the maximum levels supported by the organism to be manipulated in such a way that GH transgenics can be viable as a biotechnological tool in aquaculture.