Tadpoles develop deformed hearts and impaired kidneys and digestive systems when exposed to the widely used herbicide atrazine in their early stages of life, according to research by Tufts University biologists. The results present a more comprehensive picture of how this common weed killer – once thought to be harmless to animals -- disrupts growth of vital organs in amphibians during multiple growth periods. In recent years, worldwide amphibian population declines have fueled concerns over the potentially harmful effects of pesticides on "sentinel" organisms. Previous research had revealed negative effects of atrazine on amphibians extremely early and late in development....