I've heard of male frogs laying eggs when treated with hormones over an extended period of time. Many pollutants are either estrogens or pseudo estrogens, which means they can make wild amphibian males develop female characteristics. There was an extreme case of this shown by Tyrone Hayes on that PBS documentary a few months ago - a male Xenopus had reacted to a pollutant so strongly that it behaved as a female and laid eggs.