Some researchers have long pointed toward historical records from 200 years ago that showed a similar incidence of deformities, long before pesticides had been unleashed on the environment. Now, this opinion has been strengthened. Two reports just published in the April 30th issue of Science support the parasite argument. In California, a study linked frog deformities to a parasitic flatworm called Ribeiroia , while in the Pacific Northwest, a survey of mutated frogs revealed a pattern of malformation consistent with parasite damage. As a result of these reports, the debate has been transformed.
Any definite conclusions concerning what really threatens amphibians seem to be premature.
The direction of the investigations has focused on a single cause.