Effects of Letrozole on Growth, Sex Ratio and Sex Hormone Level of Quasipaa spinosa

PurposeTo study the effects of letrozole on the growth, sex ratio and sex hormone levels of Quasipaa spinosa, providing reference for the whole male breeding of Q. spinosa.

MethodsFeeding letrozole (20, 100, 400 and 1000 mg/kg) with different contents (recorded as L₂₀, L₁₀₀, L₄₀₀ and L₁₀₀₀ group, respectively), and the control group (CK group) was set up, the feeding cycle was 90 days. During the period of 20-70 days after hatching, the levels of sex hormones estradiol (E₂) and testosterone (T) of tadpoles in each group were measured every 10 days. After normal feeding until metamorphosis completed, the growth indicators and sex ratio of each group were measured.

ResultsThe male rate of Q. spinosa was low at (19±1) °C, the male rate of CK group was only 33.33%. Feeding different contents of letrozole could significantly improve the male rate of Q. spinosa (P<0.05), the male rates of L₂₀, L₁₀₀, L₄₀₀ and L₁₀₀₀ groups were 58.49%, 55.26%, 48.84% and 56.82%, respectively. Different contents of letrozole had no significant effect on snout-vent length, head length, head width, forearm and hand length, hind limb length and hepatosomatic index of young frogs (P>0.05). From primitive gonad to the end of gonad differentiation (during 20-70 days after hatching), compared with the CK group, the E₂ level and T level of each letrozole treatment group was significantly increased (P<0.05). During testis differentiation (during 40-50 days after hatching), the T level of each letrozole treatment group was significantly higher than that of CK group (P<0.05), which was the key to induce maleation.

ConclusionIn this experiment, letrozole has no effect on the growth of Q. spinosa, but it can improve the male rate of offspring of Q. spinosa significantly.