Giant hellbender salamanders benefit from water temperature fluctuations
The research may help scientists to understand how the species will survive in the face of climate change.
Thu, Sep 12 2013 at 3:50 PM
How will one of the world's largest salamanders survive in a warming world? It turns out that the eastern hellbender — which can reach an astonishing two feet or more in length — may be slightly more resilient to climate change than previously thought.
Here's what we already knew about hellbenders (also known as snot otters, devil dogs, mud devils, Allegheny alligators and other quaint nicknames). They thrive in cold water. They need absolutely pure water, and suffer when rivers become full of grit or pollution. And their populations are declining in all of their habitats.
But here's something new: according to research published Aug. 15 in the Journal of Experimental Biology, hellbender salamanders can withstand a greater fluctuation in water temperature than previously understood. In addition, the temperature swings appear to provide the amphibians with a greater resistance to bacteria.
"Not only were these results surprising, they were the exact opposite of what we had expected," Kimberly Terrell, the study's lead author and a scientist at the Smithsonian Conservation Biology Institute said in a prepared statement. "Clearly, we need to understand how amphibians are influenced by weather patterns in order to accurately predict whether these species can survive in a changing climate."
Terrill and her fellow researchers subjected hellbenders to simulated temperature changes at the National Zoo's Appalachian Salamander Lab. Daily temperatures changed from 60 to 80 degrees, something that could happen in the natural environment. The scientists then measured the animals for their growth rates, behavioral responses and immune health.
The assumption going into the experiment was that the fluctuations would negatively impact the hellbenders' health, either by affecting their immune functions or by creating physiological stress. The opposite happened.
The researchers tested the hellbenders' response to three types of bacteria: Pseudomonas aeruginosa, a common bacterium that can cause disease in animals; the ever-popular E. coli; and Aeromonas hydrophila, a bacterium found in warm waters that often causes diseases in fish and amphibians. After the temperature fluctuations, the hellbenders showed 70 percent greater resistance to Pseudomonas aeruginosa and 50 percent greater resistance to E. coli. Resistance to the third bacteria appeared to be unchanged.
So what does this mean? Although the hellbenders do still need cold waters to live in their optimal conditions, they — and possibly other amphibians — may have a greater ability to withstand day-to-day temperature changes, and may even benefit from those changes. As the researchers write in their paper, "Our findings highlight the need to consider naturalistic patterns of temperature variation when predicting species' susceptibility to climate change."
Eastern hellbenders are currently listed as a threatened species and are protected by state laws in most of their range. The related subspecies the Ozark hellbender was declared a federally endangered species in 2011. Both kinds of hellbenders have also been threatened by over-exploitation for the pet trade and face low sperm counts and birth rates due to human hormones being introduced to their watery habitats.
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