Exploring the Ozarks Outdoors: freshare.net

Probing Preserved Frogs for Clues

By Robert J. Korpella

First posted on 06-22-2012

If history can light our path to the present, a Yale grad student has come up with a novel means of searching the past for answers to a pathogen outbreak that is decimating amphibian populations worldwide.

Katy Richards-Hrdlicka is a doctoral candidate at the Yale School of Forestry & Environmental Studies. She’s studied the infectious pathogen, Batrachochytrium dendrobatidis (Bd), a trigger for chytridiomycosis, one of the most devastating diseases to affect vertebrates in the wild. The disease attacks an amphibian’s skin, preventing it from respiring. Infected animals die from suffocation.

First identified in the late 1990s, Bd is now found on every continent in the world, having appeared in over 200 species.

“I have long proposed that the millions of amphibians maintained in natural-history collections around the world are just waiting to be sampled,” she said. So, Richards-Hrdlicka examined 164 preserved amphibians for a historical look at the infectious disease that is driving amphibians toward extinction.

She took swab samples from the skin of preserved specimens that were collected as far back as 1963. Those specimens had been pickled in formalin at the Peabody Museum of Natural History in Connecticut.

From there, Richards-Hrdlicka used a sensitive molecular test that was capable of detecting Bd DNA, even if that DNA had been long ago fixed in formalin. The preservative chemical is a known destroyer of DNA molecules.

“This advancement holds promise to uncover Bd’s global or regional date and place of arrival, and it could also help determine if some of the recent extinctions or disappearances could be tied to Bd,” said Richards-Hrdlicka. “Scientists will also be able to identify deeper molecular patterns of the pathogen, such as genetic changes and patterns relating to strain differences, virulence levels and its population genetics.”

Richards-Hrdlicka discovered the presence of Bd in six specimens that date back as far as 1968. That is now the earliest record of Bd in the Northeastern United States. All were from Guilford, a community in southern Connecticut, near New Haven. Four other 1960s-era specimens tested positive for Bd. Those animals came from nearby Hamden and Woodbridge as well as Litchfield, some fifty miles northwest of Guilford.

By the time Richards-Hrdlicka got to specimens preserved from the 2000s, she found 27 that had been infected with Bd, all of them from Woodbridge and surrounding areas. Extrapolating from more current samples, Richards-Hrdlicka said that nearly 30 percent of the amphibians in Connecticut were presently infected, even though none as yet show symptoms.

Richards-Hrdlicka’s work helps focus attention on past events, providing valuable information to researchers scrambling for more insight into the deadly pathogen.


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