Nashville Zoo 'hell bent' on saving salamanders

[MartinS]

After several years and challenges, zoo breeds Eastern hellbenders in captivity, a first.

Two temperature- and light-controlled tanks sit in a utilitarian room tucked behind the Nashville Zoo's amphibian exhibits. Inside, two young Eastern hellbenders wriggle in semi-darkness.

Hellbenders are rare salamanders that can grow to 2 1/2 feet. For now, though, this baby pair are just a few inches long — nondescript black squiggles that won't go on display for years. They don't look like much.

But they're a huge deal to the zoo: the product of a five-year, international, biotech-aided breeding effort.

The zoo regularly works to conserve many species, from the Nashville crayfish to the clouded leopard, in projects involving anything from helping other organizations to actual breeding. But this is the first time the Eastern hellbender has been bred in captivity and the first captive breeding of any hellbender using reproduction technologies.

Those "firsts," plus the difficulty of this project, make it unusual, said Dale McGinnity, curator of ectotherms (cold-blooded critters).

"There was so much that could go wrong we didn't want to get our hopes up" in October, when it appeared the zoo had achieved fertilized hellbender eggs, said amphibian specialist Sherri Reinsch.

McGinnity was downright superstitious. "Dale didn't want to see them in person; I sent him pictures," Reinsch said. Several weeks after hatching, when the larvae began eating rather than living off their eggs' yolks, the staff finally exhaled and announced the new arrivals.

The Eastern hellbender is native to rivers in the Eastern U.S. Its numbers have dwindled since the 1990s, probably because of water quality problems, said Jeff Ettling, herpetology and aquatics curator at the St. Louis Zoo, which in 2011 bred the closely related Ozark hellbender naturally in an artificial river.

The U.S. Fish and Wildlife Service this year will consider listing the Eastern hellbender as endangered.

Tough to count
The Nashville Zoo's two larval hellbenders represent years of painstaking collaboration.

The breeding project included attempts to count how many remain in the wild. Hellbender head counts, done the old-fashioned way, are laborious.

"We've gotten really big strong guys with (logging tools) who lift giant rocks, and we have to snorkel underneath to try to find the hellbenders," McGinnity explained.

Lee University biology professor Dr. Michael Freake designed a better method, "environmental" or "e-DNA." It involves checking water samples from streams for traces of hellbender DNA, to identify whether any remain in that particular creek. This method will be used increasingly in the future, McGinnity said.

"In streams, we're only finding old males," not conducive for reproduction, said Bill Reeves, Tennessee Wildlife Resources Agency's chief of biodiversity. The agency gave the zoo a $32,000 grant for breeding hellbenders and another to Freake for developing e-DNA.

Nashville researchers learned from their St. Louis counterparts' work with the Ozark hellbender, specifically about water quality and ovulation cycles, Ettling said.

The Nashville Zoo has nurtured one female and three male hellbenders for years. Staff used ultrasound to monitor fertility and identify the sexes; outside the annual fall breeding season, it's impossible to tell males from females by sight. For two years, the female ovulated and the males' testes enlarged as expected during breeding season, but they produced no viable eggs or sperm.

In the third year, 2009, the zoo used a human fertility hormone to stimulate the males to produce milt (sperm and seminal fluid), and worked with Australian cryobiologist Dr. Robert Browne to freeze milt for use in future breeding seasons.

Later the zoo teamed with a University of Ottawa endocrinologist, Dr. Vance Trudeau, who'd developed a frog-breeding method applied to the hellbenders: injecting a hormone "cocktail" tricking the salamanders into releasing eggs and sperm.

"It is not a miracle love potion," Trudeau said. "The animals have to be sexually mature." Timing's critical, and zoo staff knew when to inject. "Then they collected eggs from females and sperm from males and mixed them together."

But still no fertilized eggs. Last fall, zoo staff tried again — and rigged a camera to remote iPhones for instant alerts.

"We came in at 3 a.m. when she laid her eggs," McGinnity said with a chuckle. "We ran around collecting sperm" — precious few teaspoons from each male — applied it to the eggs, and finally: fertilization! This fall the zoo will repeat the process, hoping for more than two larvae.

The challenges
Hellbenders are maddeningly coy; with complex mating habits, they don't exactly reproduce like rabbits. In nature, the males don't reproduce until they're 7 to 10 years old, and they, not females, guard fertilized eggs, which need to remain with daddy for at least 10 days or they die.

"There are clearly cues missing in captivity," Trudeau said. "It could be the right diet, light, temperature, vegetation, the right environment to lay eggs, enough space, etc.," he said. "Mimicking what they need is a problem."

"What's unusual about (breeding the hellbenders) is it took so long to figure them out," McGinnity said. "They're so different from everything else." It's not like breeding a frog and consequently knowing how to breed another kind of frog, he said.

So the zoo made great efforts, all for the sake of a slimy, mud-colored river-dweller that's not even part of the human food chain. Why?

"Hellbenders are such a unique organism," McGinnity said. "They're evoluntionarily distinct. Their fossil record goes back to the age of dinosaurs." The species changed little in 60 million years.

McGinnity hopes captive breeding can replenish hellbenders' numbers, but another problem is loss of genetic diversity, which protects species, long term, from disease and other threats.

Inbreeding — in captivity or when wild populations become isolated from each other — reduces such diversity. Captive breeding programs ideally maintain 90 percent of the genetic diversity of the wild population for a century.

"That takes a lot of space and keeper time," and sometimes hundreds of individual animals, McGinnity said.

"With reproduction technology, we can cryopreserve sperm and use artificial fertilization. We can maintain that genetic diversity with a lot fewer animals and a lot fewer resources," McGinnity said. "That's why we're really excited about developing these techniques."

Ettling said, "I can share their excitement. It's a big high-five moment."

Written by
Maura Ammenheuser
The Tennessean
http://www.tennessean.com/article/20130104/NEWS01/301040079/Nashville-Zoo-hell-bent-saving-salamanders?nclick_check=1

[joost.v.wijk]

Dus binnen enkele jaren is de Tijgersalamander niet meer de grootste in de hobby ;D

[MartinS]

Dus binnen enkele jaren is de Tijgersalamander niet meer de grootste in de hobby ;D

Ik ken in elk geval één lid die daar heel blij mee gaat zijn.
Of niet Niels?  ;D

[Niels D]

Ik wil hem.

[Maxim M.]

Ik wil hem.

Dat hadden de meeste mensen wel al door denk ik :D