Effects of temperature and sex steroids on sex ratio, growth, and growth-related gene expression in the chinese giant salamander Andrias davidianus

Abstract

Andrias davidianus is one of most farmed amphibians owing to its palatability and nutritional value. In this transitional group between aquatic and terrestrial animals the effects of temperature and sex hormones on sex ratio and growth are not fully understood. Here, we quantified the sex dimorphism of A. davidianus growth with adult males approximately 30% larger than females, and for the first time determined the time of initiation of sex differentiation to be ~98 days post-hatching (dph). Mortality increased significantly with increased temperature, from 9.4% at 20°C to 40.6% at 28°C. At temperatures ≥30°C we observed 100% mortality. The proportion of males was 66.1% at 28°C, significantly higher than in the control group (p < 0.05). 17α-estradiol induced larval feminization and produced female bias of 81-100% at concentrations from 25 μg l-1 to 1000 μg l-1. However, sex bias was not observed in larvae exposed to 17β-methyltestosterone at concentrations of 50 μg l-1 and 100 μg l-1. Additionally, growth characteristics at different temperatures showed that 28°C inhibited growth and 24°C promoted growth, reflecting the expression profile of growth-related genes (GH, GHR, and IGF-1). Sex steroids including 17β-estradiol and 17α-methyltestosterone significantly inhibited growth (p < 0.05). The results suggest that water temperature and sex steroids play a vital role in gonad differentiation and growth of A. davidianus.