A battle to save mountain toads from virulent fungus
Lab-grown bacteria called “Purple Rain” used to give tadpoles a fighting chance
BROWNS CREEK WATERFALL» Thousands of 1-inch black boreal toad tadpoles this week wriggled into a high alpine bog beneath mountain peaks, seemingly pristine habitat for amphibians.
But even in Colorado’s high country, they’re blinking out of existence. The culprit: a highly virulent hybridized fungus spread by humans that clumps onto their skin and penetrates, triggering massive organ failure and death.
This chytrid fungus — a main driver of a worldwide demise of frogs, toads, salamanders, newts and other amphibians —
now contaminates the farthest reaches of the planet, which scientists warn will mean trouble for people.
These boreal toad tadpoles, however, have a chance. They darted out of tubs in which Colorado scientists had bathed them in a lab-grown, anti-fungal bacteria called “Purple Rain” — like the Prince song and album — that, when coating amphibians, protects them.
Their deployment this week by University of Colorado scientists and a Colorado Parks and Wildlife team northwest of Salida marked the first large-scale test of Purple Rain in the wild. The scientists hauled 5,600 hatchery-raised toads-to-be up to this bog, bathed them for 24 hours, then set them loose. The idea is to develop a lifeline that could slow the pace of amphibian extinctions across the planet.
Nearly 50 percent of amphibians worldwide are vanishing rapidly — a trajectory scientists say will lead to extinction. That threatens humans because amphibians counterbalance insects, such as mosquitoes, that spread disease. And chemicals on amphibian skin can help fight superbugs that current antibiotics cannot stop.
Chytrid has emerged as a leading killer worldwide, along with loss of habitat, invasive species, climate change impacts on water flow, and pesticides. Colorado’s high country boreal toads, listed at the state level for a quarter century as endangered, are especially hard hit. State biologists said survivors breed at 25 or fewer sites statewide, down from 40 sites a few years ago.
“It is fairly urgent. This is one of the last regions with a breeding population of boreal toads. If this one goes under, it is dire — really in trouble, ” said Val McKenzie, the CU biologist directing this work on the frontlines of microbial ecology.
“We need a lot more conservation science support,” McKenzie said. “And, all over the world, we need better biosecurity. We need to stop moving amphibians around for aqua-culture (the industrial farming of fish, crustaceans and other organisms) and the pet trade. All that does is introduce pathogens.”
“The battle of the decline”
Boreal toads live in Rocky Mountain wetlands above 8,000 feet up to timberline. And this week’s launch of inoculated tadpoles may be the “intensive effort” without which the toads “are probably going extinct pretty quickly,” CU field crew leader Tim Korpita said as researchers crouching with pipettes drew the native strain of lab-grown bacteria (janthinobacterium lividum or “j-liv”) out of petri dishes and poured it into a quartsized jar. It looked milky. The brew takes on a purple tint when the bacteria multiply into the trillions at a CU lab inside “biosafety cabinets.”
Colorado Parks and Wildlife is helping to fund this research, and this week coordinated the rollout.
State crews had culled live eggs June 4 from a site along Cottonwood Creek west of Buena Vista and raised the tadpoles at the Native Aquatic Species Restoration Facility in Alamosa. They hauled the tadpoles north over Poncha Pass on Tuesday in truck-mounted tanks to this Browns Creek watershed northwest of Salida.
“We’re hoping they’ll re-establish,” said Paul Foutz, a state native aquatic species biologist who oversees amphibians with a focus on the endangered boreal toads. “We are fighting the battle of the decline. We are racing against time.”
Foutz cast Purple Rain as a potential “game changer” in reversing the decline of a species and said the approach of harnessing lab-grown native strains of microbes to boost defenses may be applicable elsewhere.
State officials convened a team of 40 volunteers — people such as Bryan Ward, co-owner of Salida’s Moonlight Pizza and Brew Pub — who are worried about biodiversity. Ward has helped on fish species rescues.
“Toads don’t have any less importance than fish,” he said. “They’re all part of the same ecosystem.”
The volunteers waited as state technicians scooped the inch-long tadpoles, rear legs indicating they’d metamorphosed to the brink of being toads, out of the tanks and slipped them into clear plastic bags. They closed the bags and loaded each into a backpack.
Volunteers hoisted the backpacks. They lugged them 3½ miles up to an alpine bog near Browns Creek Waterfall. CU’s six-member team had positioned plastic tubs around a pond. They dumped the tadpoles into the tubs with pond water to acclimatize and to soak overnight in the Purple Rain that — if it stays on toads — can protect against the chytrid.
In labs, the bacteria led to the production of a chemical called violacein that killed the chytrid and boosted toad survival by 40 percent, CU scientists said.
Korpita tipped the tadpoles out of the tubs into the pond starting Wednesday afternoon. This alpine bog habitat appeared somewhat compromised — spruce beetles infesting surrounding forest, cattle allowed to graze in the area — yet toads historically bred here and scientists said the pond appeared chytrid-free.
“There they go,” Korpita said as the tadpoles darted out.
Most swiftly circled back to the banks of the pond, beaching themselves. They immediately began feeding through their partially formed mouths on algae along blades of submerged grass.
“Unexplored ecology”
It will take a couple of years to determine whether the Purple Rain enables survival. Boreal toads live up to 12 years if snakes and birds don’t eat them. CU scientists, with Colorado Parks and Wildlife support, plan to monitor them regularly, catching a few to take swab samples of bacteria from the skin on their backs for analysis to measure how long the Purple Rain persists.
The chytrid fungus driving the decline of amphibians worldwide turned highly virulent after “a hybridization event” that researchers have traced to Korea in the 1950s. Global commerce spreads the fungus.
Scientists increasingly are focusing on the invisible microbial action on amphibian skin that can enable survival. Humans have a growing interest because researchers are struggling to develop new drugs fast enough to fight changing antibiotic-resistant bacteria. “We are quickly falling behind,” McKenzie said.
For amphibians, skin layers play major roles, allowing water exchange, balancing electrolytes and chemically combatting threats. Chemicals derived from amphibians have been used in developing drugs. McKenzie said researchers now are looking for broader alternative strategies to fight superbugs and see potential in deploying probiotics.
But this emerging approach of harnessing natural bacteria to boost defenses against pathogens hinges on the survival of these amphibians and the study of the microbial battles on their backs.
“We are learning things about microbial communities,” Korpita said, sloshing around the pond as the tadpoles settled in.
“This is the unexplored ecology of our world.”