Effect of Fromestane on Gonadal Sex Differentiation and Sex Ratio in the Frog, Euphlyctis cyanophlyctis , with Undifferentiated Type of Gonadal Differentiation

Analyzing the gonadal transcriptome of the frog Hoplobatrachus rugulosus to identify genes involved in sex development

BACKGROUND

The tiger frog (Hoplobatrachus rugulosus) is listed as a national Class II protected species in China. In the context of global warming, the sex ratio of amphibians will be affected, and the development of the population will be limited. Therefore, considering the potential for a decrease in the number of amphibians, studying sex evolution and molecular regulation of gonadal development in H. rugulosus, phenomenon that are currently unclear, is of great significance.

RESULTS

Here, H. rugulosus was used to explore the mechanisms regulating gonadal development in amphibians. Illumina HiSeq 3000 was used to sequence the gonadal transcriptome of male and female H. rugulosus at two growth stages to identify genes related to gonadal development and analyze expression differences in the gonads. This analysis indicated that cyp17α, hsd3β, hsd11β1, cyp19α, and hsd17β12 perform vital functions in sex development in amphibians. Specifically, the expression of cyp3α, cyp17α, hsd3β, hsd11β1, sox2, sox9, sox30, soat, cyp19α, hsd17β12, and hspα1s was correlated with gonadal development and differentiation in H. rugulosus, as determined using the quantitative reverse transcriptase-polymerase chain reaction.

CONCLUSION

Significant differences were found in the gonadal gene expression levels in H. rugulosus of both sexes, and we identified a steroid hormone synthesis pathway in this species and analyzed related gene expression, but the changes during sex differentiation were still unclear. To our knowledge, this report presents the first analysis of the H. rugulosus gonadal transcriptome and lays the foundation for future research.

The combined effects of temperature and aromatase inhibitor on metamorphosis, growth, locomotion, and sex ratio of tiger frog (Hoplobatrachus rugulosus) tadpoles

Background

The tiger frog (Hoplobatrachus rugulosus) is widely raised by many farms in southern region of China as an economically edible frog. The growth, development, and sexual differentiation of amphibians are influenced by temperature and steroid hormone level. However, the problem of hormone residues is caused by the addition of exogenous hormones in frog breeding, it is worth considering whether non-sterol aromatase inhibitors can be used instead of hormones.

Methods

In our study, H. rugulosus tadpoles were subjected to two water temperatures (29 °C and 34 °C) and three letrozole concentrations in the feed (0, 0.1 and 1 mg/g) to examine the effects of temperature, aromatase inhibitor and their interaction on metamorphosis, locomotion, and sex ratios. A G-test and contingency table were used to analyze the metamorphosis rate of tadpoles and the survival rate of froglets after feeding for 90 days. A G-test was also used to analyze sex ratios in different treatment groups.

Results

Metamorphosis time and body size (snout-vent length, body mass and condition factor) were significantly different between the two temperature treatments. Metamorphosis time was longer and body size was increased at 29 °C compared to those at 34 °C. Letrozole concentration and the temperature × letrozole interaction did not affect these variables. The jumping distance of froglets following metamorphosis was positively associated with the condition factor; when controlling for condition factor, jumping distance was not affected by temperature, letrozole concentration and their interaction. Temperature and letrozole concentration also did not affect metamorphosis and survival rate. Sex ratio of the control group (0 mg/g letrozole) was 1:1 at 29 °C, but there were more males at 34 °C. The sex ratios of H. rugulosus treated with letrozole at 29 °C and 34 °C were significantly biased toward males, and male ratio increased as letrozole concentration increased. Furthermore, more males were produced at 34 °C than at 29 °C at each letrozole concentration.