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North America's biggest salamanders, hellbenders can grow as long as 2.5 feet (0.7 meter) (file photo).
Photograph by Joel Sartore, National Geographic
Hellbender sperm-cell tail, with characteristic "corkscrew" tissue. Photograph courtesy Dalen Agnew.
Published August 20, 2010
It may be a shot in the dark, but freezing sperm is one of the last chances to save the hellbender, North America's biggest salamander, conservationists say.
Hellbenders—also known as snot otters and devil dogs—have dwindled throughout their range, which once encompassed streams from northeastern Arkansas to New York.
The 2.5-foot-long (0.7-meter-long) amphibians have declined by 80 to 90 percent in most of their traditional watersheds in recent decades, and now haunt only isolated pockets of southern Appalachia (see map), said Dale McGinnity, curator of reptiles at Nashville Zoo.
All of the states in the hellbender's range have listed the animal as a "species of special concern," and the U.S. Fish and Wildlife Service is currently reviewing whether to add the hellbender to the federal endangered species list, McGinnity said.
The reasons for their decline is unknown, but it's likely environmental contaminants such as pesticides are harming the creatures via their highly permeable skin, he said.
To make matters worse, hellbenders don't seem to be breeding at all in the wild, he said, possibly because human-made pollutants containing synthetic hormones are damaging the amphibians' reproductive systems.
As a result, there are apparently no young wild hellbenders in existence, only aged individuals—the amphibians likely live between 30 and 80 years, McGinnity said.
The hellbender's decline spurred an international team to collect sperm from some captive salamanders in September 2009 for cryopreservation, a common zoo practice that freezes sperm without damaging its cell membranes.
Though several zoos have put a "great deal of effort" into breeding the amphibians in captivity, none has been particularly successful, McGinnity added. It's unclear why they're tough to breed, but it may be that it's hard to replicate the exact temperatures of their home streams.
"For the first time, sperm was collected from a living salamander, cryopreserved, and brought back to life," said McGinnity, who is involved in the sperm-preservation effort with colleagues from Belgium's Antwerp Zoo and Michigan State University.
A sort of "insurance policy" against extinction, the sperm will enable scientists to manage hellbender breeding, according to team member Dalen Agnew, a reproductive pathologist at Michigan State University.
For instance, scientists can use the stored sperm to crossbreed individuals, he said, to ensure that wild hellbenders are genetically diverse, he said. Genetic diversity is important because if closely related salamanders breed, their inbred offspring will be weaker and more susceptible to disease.
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