Frogs’ immune systems weakened by chemicals, study finds

Frogs are exposed to flame retardants through dirt, plants and insects they eat.

Young frogs exposed to flame retardants have weakened immune systems, which could leave them more susceptible to diseases that are ravaging amphibians worldwide.

new laboratory experiment is the first to link flame retardants to immune system problems in frogs, and adds to evidence that pollutants may contribute to global declines of their populations.

Tadpoles of northern leopard frogs were exposed to polybrominated diphenyl ethers in their food from the time they could swim until they turned into frogs. Then scientists injected the young frogs with a foreign protein and found that they produced up to 92 percent fewer antibodies than non-exposed frogs.

“Making antibodies to get rid of pathogens is vital to frogs’ ability to fend off disease,” said Tawnya Cary, a postdoctoral scholar at the Institute for Biology Education at the University of Wisconsin, Madison, and lead author of the study.

Nearly one-third of the world’s amphibians – more than 1,800 species of frogs, toads, salamanders and newts – are threatened with extinction or already extinct. Chytrid fungus is to blame for devastating many populations, although other threats include habitat destruction, UV radiation and parasites.

One theory for the spread of the deadly fungus is that “pollutants alter immune function of the animals, and then they’re not able to fend off disease pathogens properly,” Cary said.

The period when tadpoles are turning into frogs – called metamorphosis – is a “very vulnerable time,” said Louise Rollins-Smith, an associate professor of pathology, microbiology and immunology at Vanderbilt University who did not participate in the study.

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About jensera

Jennifer Harrington is a Toronto-based illustrator, writer and graphic designer. She illustrated the best-selling children’s book series 'A Moose in a Maple Tree,' which includes the titles 'A Moose in a Maple Tree,' 'The Night Before a Canadian Christmas' and 'Canadian Jingle Bells.' She is also the owner of JSH Graphics, a boutique graphic design agency that specializes in print and web advertising. With her latest project, Eco Books 4 Kids, Jennifer has partnered with illustrator Michael Arnott to create a series of ecologically-themed ebooks for children. Her next book, 'Spirit Bear,' is due for release in the Summer of 2013. Jennifer offers two different school presentations for her 'Moose in a Maple Tree' collection, an illustration demonstration and a Christmas concert series, which can be booked at She will be taking bookings for school readings of 'Spirit Bear' beginning in October 2013.

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