Efeitos de hormônios sintéticos na desova, níveis plasmáticos de esteroides sexuais e transcrição de gonadotrofinas em Colossoma macropomum maduros e avaliação econômica do seu uso na produção de larvas da espécie

Abstract

The commercial production of tambaqui Colossoma macropomum can be considered a livestock activity in development in Brazil and South America. For this reason, it still presents challenges to overcome, inherent to the consolidation of any incipient zootechnical industry, in its constant search for high productivity with sustainability. Among the challenges, stands the search for commercial products to be used in the reproduction of the species, ensuring the supply of the entire production chain. This is because since its domestication, the production of tambaqui has been based on the use of crude carp pituitary extract (CPE), a biological product that represents a risk of spreading disease, and which, for this and other reasons, is being condemned by the regulatory organs of livestock products. The great challenge today, and which has been the subject of several studies in different Brazilian native species, is to identify a synthetic product (and therefore without biological risk) with the same efficacy as CPE, whose efficiency in inducing the final maturation of oocytes and ovulation in rheophilic fish is unquestionable. This theme underlies the relevance of this thesis. The objective of this work was to test different commercially available synthetic analogues of gonadotropin releasing hormone (GnRHa) in

tambaqui reproduction, to verify their effects on the qualitative and quantitative indexes of strip- spawning, sex steroid production, gonadotCorophin synthesis in the pituitary of mature males and

females, and finally, to assess the costs of their use as reproductive inducers for tambaqui. The results point to these compounds as alternatives hormones for the artificial reproduction of tambaqui, since the spawning and embryonic survival rates, as well as the investigated plasma hormones were similar in females treated with these compounds (in single doses) and treated with the tradicional CPE (two doses 12 hours apart). However, not all females treated with GnRHa spawned, unlike females that were induced with CPE. A single dose of gonadorelin (mGnRHa) upregulates lhβ expression while reducing fshβ transcription. The analysis of the costs of tambaqui larval production indicates that buserelin is very economic, however it provoked the lowest spawning index. As the analogues tested here promoted increased Lh expression, stimulated spawning with high quality and quantity of eggs, further studies are needed to optimize their dosages in order to achieve high spawning rates, at the same time as the costs involved in this practice must be considered, so that new technologies are viable for the industry, the main beneficiary of these researches.