Effects Of Feeding Steroid Hormones On The Growth,Serum Sex Hormones And Gonad Development Of Pelodiscus Sinensis Juvenile

Pelodiscus sinensis is one of the important special economic aquatic animals in China,which belongs to the Reptilia,Testudines,Trionychidae,and Pelopiscus.As males grow faster than females in P.sinensis,it is important to study the sex differentiation and gonad development.Sex hormone is a key factor in the process of sex differentiation and development,which affects the direction of sex differentiation.In this study,the effects of steroid hormones on growth,serum hormone and gonad development of P.sinensis juvenile were studied by feeding steroid hormones.Main contributions of this work are as follows:1.Effects of sex steroid hormone treatment on the survival and growth of P.sinensis juvenile?1?It is no significant difference on the survival rate of P.sinensis juvenile by feeding different doses of estradiol,while methyl-testosterone significantly reduced the survival rate.?2?Relative growth rates of body weight,carapace length and carapace width of P.sinensis juvenile in 20 mg/kg dosage estradiol groups were not significantly different from those in control group?P>0.05?.Relative growth rates of body weight,carapace length and carapace width of P.sinensis juvenile in other dosage groups were significantly decreased?P<0.05?,which showed inhibition role on the growth.?3?The relative growth rate of body weight,carapace length and width of P.sinensis juvenile showed a significant decrease in different doses of methyl-testosterone treatment groups?P<0.05?.?4?The growth of tail length of P.sinensis juvenile was significantly promoted by different doses of the two hormones,especially methyl-testosterone?P<0.05?.2.Effect of sex steroid hormone treatment on serum sex hormone and gonad development of P.sinensis juvenileEnzyme-linked immunosorbent assay?ELISA?was used to investigate the content of E₂ and T in serum of P.sinensis juvenile treated with different doses of estradiol and methyl-testosterone.The results showed that:?1?E₂ content in serum of P.sinensis juvenile increased significantly?P<0.05?and T content in serum of P.sinensis juvenile decreased to a certain extent after treatment with different doses of estradiol.?2?The T and E₂ content in serum of P.sinensis juvenile were significantly increased by feeding different doses of methyl-testosterone?P<0.05?.?3?Estradiol could promote ovarian development,furtherly,the size and number of oogonium cells were larger than those of the control group,while methyl-testosterone treatment groups was the opposite.?4?No obvious effect on the testis development was observed by using two hormones.3.Cloning and expression characterization of GnRH1 gene of P.sinensisThe cDNA full-length sequence of GnRH1 gene of P.sinensis was obtained by RACE,and the expression characteristics were analyzed by real-time fluorescence quantitative PCR?qRT-PCR?.The results showed that:?1?GnRH 1 gene of P.sinensis was 546 bp in length,in which the open reading frame?ORF?was 279 bp encoding 92 amino acids.?2?The results based on phylogenetic tree showed that the GnRH1 gene of P.sinensis and the GnRH 1 gene of Chelonia mydas,Terrapene mexicana triunguis and Chrysemys picta bellii were clustered into one.The relationship among them is close.?3?The results based on qRT-PCR showed that GnRH1 gene was expressed in 8 tissues of adult P.sinensis,both male and female,and was highly expressed in brain and gonad tissues?P<0.05?.The expression level of GnRH1 gene increased significantly with the embryo development?P<0.05?.GnRH1 gene may play an important role in the growth and gonad differentiation of P.sinensis.