Healing Hellbenders

The Ozark Hellbender may never win a beauty contest. But the giant salamander, which has a large tail, tiny eyes and a flattened body that can stretch two feet, does have a remarkable ability: it can regenerate lost limbs. So when scientists noticed that hellbenders living in some Missouri and Arkansas rivers were losing the ability to regenerate tissue – and rapidly declining in numbers – they got worried.

“We were finding animals with no legs that were still alive with flesh wounds or bones sticking out of limbs,” recalls Max Nickerson of the Florida Museum of Natural History at the University of Florida. Soon, Nickerson and a group of colleagues began studying the salamander’s skin, trying to see if a microbe, bacteria or fungi might be playing a role in the hellbender’s troubles, which helped land it on the Endangered Species list earlier this year. Now, in PLoS ONE, the team reports on their initial findings

“Scientists and biologists view amphibians as kind of a ‘canary in the coal mine’ and their health is often used as a barometer for overall ecosystem health, including potential problems that may affect humans,” says Nickerson. And “if you don’t understand an amphibian’s skin you don’t understand the amphibians,” he adds, noting that the studies could help researchers understand threats facing other amphibians.

To better understand the hellbender (Cryptobranchus alleganiensis bishop), a team led by Cheryl Nickerson of Arizona State University, cultured and identified microorganisms from abnormal and injured tissue on the salamanders, searching for pathogens that may be causing the lack of regeneration and population decline. They found several potentially dangerous pathogens, including Aeromonas hydrophila, a bacterium scientists believe is associated with disease and death in both amphibians and fish.

But no single organism was responsible for the lack of regeneration, they report. Instead, the hellbender’s problems may have many contributing factors, including disease and habitat degradation.

While some conservationists try to address those problems, others are taking another approach: The St. Louis Zoo recently bred hellbenders in captivity for the very first time. David Malakoff & press materials | December 20, 2011

Source: Nickerson CA, Ott CM, Castro SL, Garcia VM, Molina TC, et al. (2011) Evaluation of Microorganisms Cultured from Injured and Repressed Tissue Regeneration Sites in Endangered Giant Aquatic Ozark Hellbender Salamanders. PLoS ONE 6(12): e28906. doi:10.1371/journal.pone.0028906

Image Courtesy USFWS