Abstract: The individuals of tadpoles Rana chensinesis at stages 26-28 were exposed to 0.05-0.5 mg nonylphenol (NP) per liter water to estimate the acute toxicity effects of NP. The results showed that the regression equations between the individuals’ death probability and the logarithm of NP concentration for 24, 48, 72 and 96 h were y=8.4087x+10.202, y=9.5104x+11.745, y=10.284x+12.498， y=10.619x+13.095, with the mean LC₅₀ values being 0.24, 0.20, 0.19 and 0.17 mg·L^-1 respectively. The safe concentration (SC) was 0.017 mg·L^-1, and the 96 h LC₀ value was 0.14 mg·L^-1, suggesting that the death probability of tadpoles R. chensinensis individuals had a positive linear correlation with definite range of NP concentrations. In order to examine the effects of lower concentration NP on the growth and development of R. chensinensis, the individuals at stage 26 were continuously exposed to 100, 60, 30, and 10 μg·L^-1 of NP till metamorphosis, with 3 and 0.3 μg·L^-1 of E₂ as positive control. The body mass, total length, and the duration of metamorphosis were determined at 20 days, 40 days, and after metamorphosis. It was shown that <100 μg·L^-1 of NP had no effects on the mortality of tadpoles R. chensinensis, while 10 and 100 μg·L^-1 of NP had the similar effects of 3 μg·L^-1 E₂, i.e., delayed the time of metamorphosis, and decreased the body mass of froglets after metamorphosis. It was suggested that NP with the concentration of <100 μg·L^-1 did not directly damage the organism, but disrupted its endocrine activity to affect the development of tadpoles R. chensinensis.

Key words: Community structure, Biodiversity, Spatial distribution pattern, Interspecific association