Impact of injection of different hormones on gonadosomatic index and expression of gonadotropin genes(GtHα,FSHβ,LHβ)in female marbled eel(Anguilla marmorata)

In order to study the effect of different hormones injection on marbled eel Anguilla marmorata ovarian development and to clarify the role of two gonadotropins in the process, this paper compares the induction effects treated by different hormone combinations through GSI(Gonadosomatic index), and a quantitative study by real-time fluorescent quantitative PCR(qRT-PCR)was applied to analyze the expression of the pituitary gonadotropin hormone subunits: GtHα, LHβ and FSHβ genes at different developmental ovary stages. The results showed that combination of CPE(carp pituitary extract)and hCG(human chorionic gonadotropin)can effectively induce the gonadal maturation of eels with GSI significantly increased. However, injection of androstenedione(ADSD)alone and mixture of ADSD, CPE and hCG didn't have significant impact on GSI which varied within 1%-3%. The results of quantitative fluorescence PCR showed that expression of LHβ and GtHα significantly increased among the CPE and hCG treated group, while the expression quantity of FSHβ was down-regulated. In conclusion, CPE and hCG could successfully induce female maturation, while injection of ADSD into female eel had no induction of gonadal development; meanwhile, LH plays a vital role in gonadal development in A. marmorata, and FSH plays a key role in early gonadal development, indicating that the FSH may be the key factor inducing the early development of eel's ovary.