Biologia reprodutiva e expressão gênica gonadal em Genyatremus luteus (BLOCH, 1790) - (Teleostei, Perciformes: Haemulidae)

Abstract

Genyatremus luteus, popularly known as stonefish, is an estuarine-marine species with a preferentially coastal habitat, living especially in estuaries and lagoons. This species has great potential for extractive fisheries in the state of Maranhão. However, little is known about the reproductive biology of this species. Thus, the objective of this work was to evaluate the reproductive biology and gonadal gene expression in G. luteus on the island of Maranhão. 21 male and 28 female specimens were used. According to the histological characteristics of the testes observed in the histological analysis, males were grouped into three reproductive stages: immature (n=7), maturing (n=7) and mature (n=7) and females, in turn, based on the histological characteristics of the ovarian follicles and the development of the oocyte were also classified: immature (n=7), maturing (n=7), mature (n=7) and spawned (n=7). Plasma levels of hormones E2, 11-KT and 17α-OHP were measured by enzyme immunoassay (ELISA). Estrogen (er) and LH (lhr) receptor gene expression was analyzed by real-time PCR. In males, the plasma concentration of 11-KT showed a peak in the final maturation phase. The highest plasma concentrations of 17α-OHP were found in the immature stage, which decreased in the subsequent stages. On the other hand, 17β-estradiol (E2) showed higher concentration in the maturation stage. The expression of er significantly increased along the maturational development of the testes. The mRNA for the LH receptor decreased from the immature stage to the maturation stage with a consequent peak of expression in the mature stage. There was a high correlation between receptor gene expression and plasma steroid levels, especially with E2. In females, the highest plasma concentration of E2 was found in mature specimens. Plasma concentrations of 17α-OHP increased significantly from the immature stage to the final stage of ovarian maturation. The maturational reproductive stage had no effect on plasma 11-KT concentrations. The expression of er in the ovaries significantly increased throughout ovarian maturation and remained high in the maturation and spawning stages. The expression of lhr showed a similar trend throughout the maturation process, although it reached its peak in the spawning phase. In conclusion, this study characterized for the first time, under the cellular, endocrine and molecular aspects, the different stages of reproductive maturation in males and females of G. luteus, demonstrating that the gene expression profile for er and lhr receptors, as well as plasma concentrations of 11-KT and E2 were directly related to testicular and ovarian maturation, although not necessarily related to the gonadosomatic index.