Uso de diferentes técnicas na avaliação do sexo e estágio de maturação gonadal em Astronotus ocellatus

Abstract

Considering the economic importance, as well as the scarcity of studies applied to the reproduction of the Oscar fish (Astronotus ocellatus), the general objective of this study was to evaluate the methods for identifying the sex in this species, such as dosage of sexual steroids (testosterone and 17β-estradiol), ultrasonographic evaluation of gonads, morphometric evaluation and gonadal histology. A. ocellatus specimens with 12 months of age, in a total of 20 animals, were used for this study. Blood samples were collected for hormone dosage of testosterone (T) and 17β-estradiol (E2). Coelomic ultrasonography, morphometric evaluation and gonadal histology were also performed on the specimens to confirm sex and assess gonadal maturation. The data obtained from the analyzes were correlated to the sex of the animals at 5% significance using the Minitab® program version 18 (Minitab LLC, Stage College, PA). After histological evaluation, the presence of 13 females and 7 males were verified, with 40% in initial maturation, 15% in final maturation, 20% mature, 10% spermed/spawned and 15% at rest. None of the tested animals was characterized as immature. The morphometric data did not show statistical differences (p>0.05), however the hormonal analyzes showed a statistical difference regarding the T/E2 ratio between males and females (p=0.013) and showed 78.94% effectiveness in predicting sex. The results of gonadal ultrasonography showed different echogenicity with hyperechoic patterns of mature ovaries in relation to hypoechoic patterns of maturing ovaries. Males, on the other hand, presented an anechoic pattern in the testicular region. It can be concluded that under the conditions in which the experiment was carried out, the sexing method by hormone dosage was validated. However, the morphometric data were not efficient for gender prediction. The data obtained by ultrasonography, although promising, require further work with a larger number of animals in different age groups for validation of the technique.