Whichever path to adulthood the newt chooses, it can’t reproduce on land. Newts need to breed and lay their eggs in water. The breeding season begins in September, and females will mate with several males over the course of a season, storing sperm for up to a year before using it to fertilize their eggs. Mating involves males performing a little dance for the females, then clasping their backs in “amplexus” before depositing a spermatophore for the female to pick up.

Many adult newts will leave their pond and overwinter in the forest, but some will stay active throughout the winter months — a rare occurrence for amphibians.

“Unlike most temperate amphibian species, which breed in spring or summer and burrow in soil or sediment during the winter months, newts have aquatic adults that start breeding from early autumn until the following spring in permanent ponds, making it possible to sample newts year-round from the same habitat,” said Thomas Raffel, an expert on amphibian parasitism whose Ph.D. thesis centered on eastern newts.

No one knows exactly why some eastern newts choose to keep breeding under the ice while others take shelter in the forest with the rest of the amphibians. Raffel suggested they were “obviously keen to do a lot of breeding that year.”

Some adult eastern newts stay active under the ice all winter long. Image by Thomas Raffel.

“Partly because they’re so abundant, partly because they’re one of the few predatory aquatic amphibians that are actually present for most of the year, and not just during a short breeding season, we’re talking about a species whose loss or decline could have a big impact on ecosystem function in wetlands,” Raffel said.

Fortunately, eastern newt populations are currently doing well. Since efts and adult newts are toxic, many predators will avoid them, and their ability to adapt and spread means they currently face few conservation concerns. But a fungal pathogen from Asia could be about to change all that. Scientists are worried it could decimate U.S. salamanders, including eastern newts, and wreak havoc on pond ecosystems across the eastern U.S.

A pandemic on the horizon

Bactrachochytrium salamandrivorans, or Bsal for short, has been given the Latin name “salamander devourer” for a reason. In 2008, an outbreak of the fungal pathogen was detected in the Netherlands. A few years later, it had wiped out more than 90 percent of the country’s fire salamanders and spread to neighboring Belgium and Germany.

Experts believe Bsal was most likely introduced to Europe by the international pet trade; the fungus is found naturally coexisting with salamander populations in Asia, but it has proved deadly to salamanders that did not evolve with the pathogen in their native environment. And it could take just one unwanted pet set loose into a stream to unleash an epidemic.

Now, with the Netherlands serving as a dire warning, scientists and policymakers in the U.S. are desperately trying to take steps to detect and minimize the damage from Bsal when it reaches North America. “We can avert another disease-mediated mass mortality of amphibians if we are proactive as a community, that effort includes academia, NGOs, governmental agencies, and the public,” Longo said.

So far, proactive measure have involved instating a pet trade ban, testing U.S. salamander species for susceptibility to the fungus, and swabbing 10,000 salamanders for Bsal in locations where it has been deemed most likely to enter the country. The survey turned up zero cases of infection, but even with measures taken to delay its arrival, most scientists believe it’s a case of when — not if — Bsal will arrive on U.S. shores.

The next step is determining management measures to limit the damage Bsal does once it hits the world’s salamander biodiversity hotspot. Understanding how certain species might react to and spread the fungus is critical, and eastern newts are at the top of that list.

The eastern newt is both a critical part of its ecosystem and an important model organism for studies on limb regeneration, skin toxins and predator-prey dynamics. It’s also alarmingly susceptible to the fungus and highly likely to spread it across North America.

Typical ulceration and inflammation resulting from Bsal chytridiomycosis in the eastern newt. Image by Alberto L. López-Torres.

A study has found Bsal to be fatal to eastern newts in 100 percent of test subjects, and researchers say this means the species will likely fare poorly if Bsal gets to the U.S.

“We expect that we would see widespread die-offs and population declines in eastern newts if Bsal invaded North America,” said Karen Lips, an amphibian disease expert at the University of Maryland, College Park, and co-author of the study.

Longo is currently working with a team researching how Bsal might interact with Bactrachochytrium dendrobatidis, or Bd, a related fungal pathogen already present in American salamander populations. While Bd has caused mass mortality in some frog species, salamanders can survive infection. In fact, Longo has found that some populations of eastern newt have an 80 to 100 percent prevalence of Bd.

Right now, it doesn’t appear to be causing much of a problem, but preliminary results of Longo’s research show that Bd could have an immunosuppressing effect that makes it harder for newts to fight off Bsal. Using eastern newts to study interactions like these is important not only for eastern newts, but also to understand how Bsal might affect closely related species like the endangered black-spotted newt (Notophthalmus meridionalis). It is also critical to understanding where eastern newts might disappear and how that could affect the ecosystems they inhabit.

Because eastern newts are so widespread and so good at migrating, experts are concerned that they could play a major role in spreading Bsal once it arrives.

“Eastern newts are one of the most mobile amphibian species, and if they’re carrying something, they could be a really important vector of moving disease across the landscape,” Raffel said.

Longo was unequivocal in her assessment: “Without a doubt, all the evidence is showing that eastern newts will be super-spreaders of Bsal,” she said. “We know that eastern newts will have a key role in the emergence of Bsal, therefore we need to focus on ways to control the infection in this particular species.”

Amphibian disease ecologists and policymakers have their work cut out for them, but none question the importance of remaining one step ahead of Bsal if it could mean saving species like the eastern newt.

“The prospect of possibly having the collapse of eastern newt populations on a large scale would, to me, be really frightening,” Raffel said. “We don’t know how much of an impact the loss of eastern newts would have on pond ecosystems, but it could be something analogous to the loss of wolves in Yellowstone.”

 

 

Banner photo: An eastern newt eft. Image by Steven Kersting (CC BY-NC-ND 2.0).

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Article published by Morgan Erickson-Davis
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