NCPA - National Center for Policy Analysis

Common Parasite Deforms Frogs

April 30, 1999

Environmentalists who rushed to blame chemical pollutants for deformities in frogs have something new to think about. Field surveys and lab experiments indicate that small parasitic flatworms known as Ribeiroia trematodes can infect tadpoles, causing their legs to grow abnormally, according to a report in today's issue of the journal Science.

  • Frogs with missing, deformed or extra legs have been found have been reported throughout the U.S. and in parts of Canada -- leading some environmentalists to speculate that pollutants or exposure to ultraviolet light because of ozone loss were responsible.
  • Scientists, however, have always suspected that some natural cause must account for at least some deformities since abnormal limbs have been observed in amphibians for hundreds of years.
  • Hartwick College biologist Stan Sessions has determined that structures in malformed frogs he has studied were not consistent with experimental evidence suggesting that a class of chemicals called retinoids might cause such defects.

Some environmental researchers still contend that chemical contaminants can cause limb deformities and more studies are needed.

Source: William Souder, "New Suspect in Deformed Frogs," Washington Post, April 30. 1999.


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