Together with its cousins, the Japanese and Chinese Giant Salamanders, the hellbender is one of the largest amphibians in the world, and part of the only group of animals that can breathe mostly through folds of excess skin between their front and back legs. They're a strange creature worth investing in, especially now that their numbers are declining to the point where certain populations are dying out altogether, so researchers have developed new assisted reproductive technologies to help keep these slimy salamanders around.
Hellbenders are endemic to North America and are split into two subspecies, the eastern hellbender (Cryptobranchus alleganiensis alleganiensis), which is found throughout the eastern states, and the Ozark hellbender (C. a. bishopi), which is restricted to the Ozark Mountains of northern Arkansas and southern Missouri. Both males and females grow to around the same size, stretching 24 - 40cm (9.4 - 16in) and weighing in at a rather hefty 1.5 - 2.5kg (3.3 - 5.5 lb). While many sources will tell you that we don't really know where their common name 'hellbender' came from, its first use can be found in the 1812 book, A memoir concerning an animal of the class of reptilia, or amphibia, which is known, in the United-States, by the names of Alligator and Hell-bender, by American naturalist Benjamin Smith Barton. And let's just say he was a man of his time...
"I must not omit to mention a very singular name by which this animal is known in some parts of the United States. By the negroes in the western parts of Virginia, on the waters of Holsten where it is common, the reptile is often called Hell-Bender, by reason of its slow, twisted motions when moving in the waters, which the slaves compare to the torturous pangs of the damned in hell. It is beneath the dignity of natural history to notice such vulgar names, when they serve to throw any light upon the habits or economy of an animal? And does not the moralist perceive, that there is something melancholy and distressing in the condition and reflections of those who impose such names?"
Barton, who was the first to describe the species, decided that the Native American name for the creature, 'Tweeg', was more fitting, but despite his best efforts, it did not stick nearly as effectively as hellbender has. Other nicknames it has acquired along the way are devil dog, ground puppy and snot otter.
Over the past couple of decades, the eastern hellbender has been experiencing drastic declines throughout its range, and researchers aren't quite sure why. It could be the degradation of water sources that feed into their streams, new diseases or new pollutants being introduced to their streams, or a combination of all three, and its causing what's known as a lack of recruitment, which means young hellbenders are not growing up in declining populations, leaving fewer and older individuals for breeding each year. Plus dams and polluted rivers have already relegated them to the few healthy streams that are left, which has resulted in many isolated populations that could develop genetic defects because of inevitable inbreeding.
"Our hellbenders (Ozark and eastern), and the Japanese and Chinese Giant Salamanders are the only three species in the family Cryptobranchidae ... and this family contains the largest amphibians in the world. All three species are imperiled and may disappear unless conservation programs are developed for them," says Dale McGinnity, the ectotherm curator at the Nashville Zoo, and part of the team that has recently launched the first captive breeding program for eastern hellbenders.
Hellbenders are a difficult species to breed in captivity, and getting a hold on wild individuals to bring back to the lab is no walk in the park either. “Catching hellbenders is tough work because they live under large stones in rivers and streams,” says McGinnity. “We have to get several big guys with log peaveys (a log-moving tool) to tilt the rocks up, so that one of us can snorkel underneath to see if hellbenders are present.” However, determining if hellbenders are still present in given stream will be easier in the future.
Funding from a collaborative SWG grant (State Wildlife Grant) through the Tennessee Wildlife Resources Agency supported statewide surveys, disease testing, gene banking and genetic analysis for Tennessee hellbenders. The grant also funded the development of a new technique called eDNA (environmental DNA) for determining if hellbenders are still present in a stream from minute amounts of DNA taken from a 1 litre sample of stream water. The grant funded McGinnity’s work at the Zoo and in the field Brian Miller from Middle Tennessee State University, who has done the most research on hellbenders in Tennessee over the last 25 years documenting declining populations, and Michael Freake from Lee University in Tennessee who did the eDNA and genetic work.
It’s taken a team at St Louis Zoo in Missouri many years to be the first to successfully breed Ozark hellbenders in captivity, which they did last year for the first time, by keeping them in large artificial stream systems. “The natural breeding at St Louis is great, and will produce many animals for release in the future, but the genetic variability of these offspring is somewhat limited,” says McGinnity.
Working instead with the eastern hellbender subspecies, McGinnity's team at Nashville Zoo are developing new reproductive technologies to breed them in a laboratory setting, which, when perfected, will hopefully produce large numbers of genetically diverse offspring for reintroduction into the wild.
The Nashville Zoo's project launched about five years ago, with three male hellbenders and one female from a healthy wild population. It became an international collaboration, including Australian cryobiologist Robert Browne from the Zoological Society of Antwerp, who is an expert in amphibian reproductive technologies, and together they came up with painless techniques for collecting and cryopreserving sperm from captive and wild hellbenders to build up a large, cryopreserved gene bank.
Over the past couple of years, the team has also been using a new hormone injection called Amphiplex - recently developed for assisted reproduction in frogs - to stimulate egg and milt (seminal fluid) production in the captive hellbenders. "At the Zoo, we had been doing a long-term ultrasound study on the reproductive organs of our hellbenders over the seasons. By using ultrasound to determine the exact right time to inject the Amphiplex, based on the development of the testes and follicles, we have been able to reliably collect both eggs from the female and strip milt from all the males over the last two years," says McGinnity. "We then place the sperm on the eggs and test different variables to see which might work." Last month they announced that they were finally able to produce two healthy hellbender babies using freshly collected sperm.
"We need to further develop fertilisation protocols and early egg incubation techniques to produce large numbers of offspring, but we feel confident that we will be able to do this in the near future," says McGinnity. “We are not fully there yet, but our hopes for the project will be to produce genetically appropriate stock for reintroduction, and slow down the loss of genetic diversity in declining populations through gene banking.”
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