Abstract:
Declining of Amphibian species has become a worldwide problem today. Habitat fragmentation and alteration, UV radiation, climate change, diseases, contaminants and nitrogenous fertilizers can be considered as the main reasons. Present study was carried out to investigate the effect of urea on the development of the endemic arboreal tree frog Polypedatus cruciger. Urea is the most common nitrogenous fertilizer used in the country. Samples of foamy egg masses of P. cruciger were collected from sites in Wellamadama, Matara, and Thelikada area, Galle District. The Lethal Concentration (LC50) of urea on 10-day old post-hatched tadpoles was determined using Probit Analysis. After the estimation of LC50, the tadpoles were exposed to three sub-lethal concentrations 7.0 g/L, 7.5 g/L and 8.2 g/L of urea, and the effects on growth and morphology of tadpole stages of P. cruciger were studied. The impact of sub-lethal concentrations of urea for the snout-vent length and weight showed significant difference (p<0.05) and strong negative correlation (Spearman’s rho correlation coefficient= -0.405 and -0.436 accordingly) when compared to the control. The observed external morphological changes under the laboratory conditions included edema formation, abdominal lesions, colour change and rupturing of tadpoles. Since water bodies in agro ecosystems contain diverse fertilizers and pesticides, their impacts on amphibians in the field may be severe due to their synergistic effects. This may cause severe declining in amphibian species, which have their developmental stages associated with water bodies in agro eco systems.
