Since the 1990s, herpetologists have watched in horror as amphibians have vanished from every ecosystem where they once hopped, crawled, and swam. In tandem with habitat loss and a warming climate, the global amphibian decline was quickened by a prolific threat: Batrachochytrium dendrobatidis, a fungal pathogen known as Bd or “chytrid” fungus. Bd rode the backs of amphibians from one continent to the next. Karen Lips, an associate professor of biology at the University of Maryland, witnessed the carnage firsthand in Central America.
“I started noticing dead frogs everywhere,” says Lips. At her study site in Western Panama in 1993, she recalls the fungus was pervasive. “We’d see frogs that looked healthy. But when we picked them up, they would jump once, and then die right on the ground.” Lips has since become one of the world’s leading experts in amphibian diseases.
Like a Hydra, chytrid fungus recently reared a new head: Batrachochytrium salamandrivorans, or Bsal, a fungal pathogen that targets salamanders. First described in 2013, Bsal began infecting fire salamanders in the Netherlands. It has not yet appeared in the U.S., where most of the world’s salamander species live.
But if the infections follow Bd’s patterns, says Lips, Bsal will almost certainly claim many of North America’s salamanders. Our best hope, she believes, is to enact new laws that would stop people from importing infected wildlife. Between her two presentations at the February 2016 meeting of the American Association for the Advancement of Science in Washington D.C., Lips sat down with SciCom’s Brendan Bane to discuss the outlook for salamanders.
When did you first become interested in amphibians?
As an undergraduate, I wanted to take all of the “ology” classes: mammalogy, ornithology, herpetology. I ended up taking herpetology first. My professor took the class out on weekend field trips where we collected animals from all over the state. I ended up working for him. At the time I was working at the mall for minimum wage, which was $3.15 an hour. My professor offered to pay me to catch turtles for $7 an hour, so that was easy math.
Then I got hooked on herpetology. I took a year off to intern at Archbold Biological Station in South Florida, where I studied gopher tortoises and the animals that lived in their burrows. Someone there told me about the golden toads in Costa Rica. Once I saw the frogs, that was it.
Many people know about Bd, the form of chytrid fungus that worsened the global amphibian decline. But you mentioned the new form, Bsal. Let’s start simply: What is chytrid fungus?
It’s a group of fungi, but nothing like the mushrooms you might imagine. It’s microscopic. Its life cycle has two stages. In the first, it looks like a little sperm or tadpole. It has a tail it uses to swim through water to get to a new frog or host. It burrows into the skin, drops off its tail, embeds itself, and morphs into its second life stage, which looks like a capsule filled with spores. The spores mature, the capsule breaks open, they swim out, and the frog or salamander is reinfected.
How do Bd and Bsal differ?
Bd creates a lawn of fungus in the skin of the frog or salamander. Bsal, however, creates a localized lesion. In European fire salamanders, for example, when they have a bad infection, they get little ulcers around their face and eyes. Reports say that while Bd is a lawn, Bsal is more localized—like little volcanoes of disease.
How do Bd and Bsal kill amphibians?
With Bd, you get one infection. It spits out ten more spores, and it grows and grows. Soon the skin gets completely filled. If you look closely at infected frogs once they’re dead, they have more fungi cells than frog cells in their skin. They’re just that abundant.
The fungi’s little capsules physically block the skin. That alone causes huge problems for frogs and salamanders. Many amphibians have no lungs. They absorb water and get rid of carbon dioxide right across their skin. Their skin is their lung. So the animal tries to shed its skin to rid itself of the fungus. That briefly helps, but they can’t keep shedding, and they quickly get reinfected.
The fungus blocks them from breathing, but it also kills amphibians a second way: by turning off parts of a frog’s immune system. When we get sick, our immune system responds by sending out T and B cells that go out and kill evil virus particles. That’s what the frog immune system should be doing. But the fungus manipulates the frog’s genetics and turns genes off, so it can’t produce enough T and B cells.
"I think there’s very little we can do. It’s unclear even what we should do."
Does Bsal suffocate like Bd?
We don’t know. It’s too early to say.
Are North America’s salamanders at risk?
They’re already in decline, and more threats like this new chytrid fungus are on the horizon. It isn't here yet, apparently, but everyone is worried it will be. If it does get here, we know that many of our species are susceptible. Since our salamanders have really broad distributions, if one gets infected, it will quickly spread across the country.
What can the average person do to help?
Encourage your representatives to stop the import of animals without testing. We have laws that require testing of anything that can bring a human disease, so live primates and any plant or animal that might unleash an agricultural pest or pathogen gets tested. These things are regulated so that when we import live animals, they don’t bring nasty parasites or pathogens with them.
But that leaves most wildlife unchecked because they don’t fall under any of the existing categories. Amphibians, reptiles, many fish, and some birds and mammals are imported without testing because there’s no legal requirement for them to be tested.
None at all?
Zero.
That’s incredible.
It is. The U.S. Fish and Wildlife Service recently instituted a ban on a subset of some salamanders. That’s great. That works. But it’s a very clunky tool. They can’t actually list or test for the disease itself. It would be better if they could just say, “don’t import anything that might have a disease and here are things to watch out for.” But they only have the Lacey Act, which says you can’t import certain animals. It says nothing about parasites or pathogens. So if you wanted to control Bsal or Bd, you’d have to list the host animal, which is crazy. It’s the most clunky application, but it’s the only law they have.
This is where Congress needs to step up and create a new law that prevents the importation of invasive diseases in wildlife or requires testing live animals being imported. As of now, we don't even know what’s coming in. It’s like we’re blind.
What makes salamanders worth protecting?
Because they’re cool, right? And they’re useful. They eat bugs, like the mosquitoes that spread Zika, malaria, or dengue. They offer all sorts of medical and biotech opportunities. The red spotted newt, for example, can regenerate up to half its heart. You can imagine doctors being very interested in figuring out how that works.
And they’re important ecologically, of course. They supply food to predators and regulate algae and insects in streams and ponds. When they metamorphose, they bring nutrients from one habitat into another.
What can zoos and museums do to help?
They’re kind of against the ban. When they move animals betweens zoos, they have to apply for permits, and that’s a hassle. We all have to do this now. But if you claim to be a conservation organization, you should support it, despite the annoyance.
Have you seen any promising adaptations in the wild?
People look for obvious things like genetic changes, but that requires material from before the decline. We don’t have that for most places. We almost never have the “before.” We have a lot of “after.” Everything is infected or declined or missing. So how do you compare it to what was there before?
Museums can make collections when there’s a permanent historical record in the form of specimens, tissues or genes. We could look and see how they differ from now and from 50 years ago.
How did you feel when you first noticed the decline?
I first noticed it when I was a graduate student. I left my field research to go home for Christmas. When I got back, the frogs weren’t there. I thought, “Well, it’s kind of dry and the rain hasn’t settled yet.” I waited and waited, but they never came back.
That was before chytrid fungus was described and before anyone knew what was going on. I knew something similar had happened in Monteverde, Costa Rica. So I went south to another study site in Western Panama to look there, and because I had no more frogs to study.
One day, I started noticing dead frogs. In three weeks we found 50 dead frogs. We took some of the sick frogs back to the lab, but they died before we got home. I thought, “This is it. Whatever this is, this is it.”
What’s our best strategy is now?
We have to get way more involved on a conservation level. We can’t just hope for the best and see what happens. We have to start asking questions. Did we cause this decline? Did we contribute? Which species get selected and what are the criteria we’re going to use to prioritize them? There are no answers, of course. But we need to start asking.
I also think we have to come up with a systematic, scientific approach to either turn off genes in the fungus, or help the frogs and salamanders adapt to a world of fungus. That may mean leaving them out there. It may mean bringing them in, raising them, continually putting them back out there, and hoping we eventually get the right genetic combination that can handle the fungus.
Are you at all optimistic about the future of amphibians?
No, not really. I think there’s very little we can do. It’s unclear even what we should do. Should we leave the frogs out there and give them a chance to adapt? Or should we bring them into captivity and let them sit in a box until something magical happens, the problem is solved, and then put them back out?
Our first response used to be to bring them in and stick them in a zoo until the problem passed. Well, today’s problems don’t go away. You can’t get rid of this disease.
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© 2016 Brendan Bane. Hop through Brendan’s collected work at brendanbane.wordpress.com.
