Picture something straight out of a science fiction movie. On mountaintop glaciers of Alaska, Washington and Oregon, billions of tiny black worms are tunneling upward to the barren, icy surface. Measuring about a half-inch in length and thin as threads of dental floss, ice worms (Mesenchytraeus solifugus) dot glaciers throughout the Pacific Northwest, British Columbia, and Alaska. Vast numbers of the tiny black worms emerge on summer afternoons and evenings to feed on algae, microbes, and other detritus on the surface.
Yet here’s where the story takes a darker turn. But as glaciers are vanishing, so are ice worms. “We want to find out as much about the worms as we can before they disappear,” says Shirley Lang, a biologist at Haverford College in Pennsylvania. The clock is ticking for these remarkable creatures as their frozen world melts beneath them. Ready to discover what makes these mysterious beings so incredible, and why their story might be coming to an unexpected end?
The Ice Worm: Nature’s Frozen Paradox
Yes, ice worms do, in fact, exist! They are small worms that live in glacial ice in Alaska, Washington, Oregon, and British Columbia; they have not been found in glaciers elsewhere. Ice worms are the only annelid worms known to spend their entire lives on glacier ice.
These tiny creatures represent one of nature’s most extraordinary evolutionary achievements. These distant relatives of earthworms survive in layers of ice-cold water within the snow and ice, thriving at water’s freezing point. This would be impossible for most creatures, especially cold-blooded ones without any insulation, like worms. Their very existence challenges everything we thought we knew about life’s limits in extreme environments.
M. solifugus is dark brown and grows to about 15 mm long and 0.5 mm wide. It has a high population density and is common in suitable habitat. Despite their diminutive size, their impact on glacial ecosystems is anything but small.
A Vanishing World
The Nisqually Glacier, on the south side of Mount Rainier, home to ice worms, has retreated significantly, with documented retreat of approximately 150 feet between 2003 and 2008. This relentless retreat isn’t just a local phenomenon. The recent rapid retreat of North Cascade glaciers, a loss of 20-40% of their entire volume since 1984 and the disappearance of 8% of the glaciers we monitor is of great concern.
The total population of ice worms must be decreasing as North Cascade glaciers continue to retreat rapidly and even disappear in some cases. Make no mistake their habitat has been shrinking with glacier retreat. The mathematics are stark: less ice equals fewer places for ice worms to call home.
The alarming reality becomes even clearer when you consider specific cases. At the end of the summer 2023 melt season only three of these remain as glaciers, Daniels, Foss and Lynch Glacier. The area loss from 1986 to 2015 was 0.07 km2, which is less than the area loss from 2015 to 2023 of 0.08 km2. The acceleration of glacier loss is frightening when viewed through the lens of ice worm survival.
The Scientists Racing Against Time
“I feel like I need to rush to study these animals,” Hotaling says. To beat the ticking clock, Scott Hotaling, a biologist at Washington State University, makes sure that as soon as ice worms appear on the mountain’s Paradise Glacier, so does he. Hotaling is one of the few people who actively studies this species.
Joanna Kelley, an evolutionary geneticist, and Hotaling are working to sequence the worm’s genome, which has proved difficult. That’s partially because they’re so full of melanin, which clings to DNA and interferes with genome sequencing technology. They hope to uncover their other secrets before it’s too late.
The urgency in scientific circles is palpable. “And I have little doubt they will disappear one day,” if glaciers continue to melt at their current rate. These researchers aren’t just studying ice worms for academic curiosity; they’re conducting what may amount to a rescue mission for scientific knowledge.
Temperature’s Deadly Dance
M. solifugus have a very narrow acceptable temperature range. Their metabolisms have adapted to cold temperatures, and they are the only known worm to spend their entire life in temperatures near 0 C (32 °F), where they are most active and their ability to produce adenosine triphosphate (ATP) is at its peak. Yet this specialization comes with deadly constraints.
When ice worms are exposed to temperatures as modest as 5 °C (41 °F), their membrane structures disassociate and fall apart (i.e., “melt”) causing the worm itself to “liquefy.” Imagine living in such precise conditions that a few degrees of warmth would literally cause your body to fall apart.
Despite spending most of their lives encased in ice, ice worms cannot tolerate freezing and will die if temperatures are less than 0º C (32º F). This paradox makes them exquisitely vulnerable to the temperature fluctuations that come with a changing climate.
The Mystery of Their Daily Lives
Ice worms retreat beneath glacial surfaces as daylight begins to hit the glaciers in the morning, and then ice worms return to glacial surfaces within several hours of sunset. Ice worms retreat beneath glacial surfaces as daylight begins to hit the glaciers in the morning, and then ice worms return to glacial surfaces within several hours of sunset. The species name of solifugus means “sun-avoiding” in Latin. This name was given to the species because of its natural tendencies to retreat back under glacial ice surfaces before dawn.
These thread-like worms, each only about an inch long, wiggle up en masse in the summertime, late in the afternoon, to do – what? Scientists don’t know. After decades of research, this fundamental question about their behavior remains unanswered.
For instance, we don’t know why they emerge in the summer, or why they spend most of their lives buried deep in ice. Further, what they do underneath the ice for so long is a complete mystery. The ice worms’ secretive nature adds another layer of urgency to conservation efforts.
Ecosystem Engineers in Black
With an area of 2.7 square kilometers, this represents somewhat potentially millions of ice worms on this glacier, representing extraordinarily high population densities on just one glacier. Such staggering numbers hint at the ice worms’ crucial role in their frozen ecosystems.
These worms support glacier ecosystems by breaking down organic debris and algae. In doing so, they add nutrients to the glacier meltwater, which in turn feeds insects, moss, and downstream forests. They’re essentially the recycling centers of the glacier world, processing organic matter and making it available to other life forms.
Already, the researchers have spotted birds chowing down on ice worms. Those known to peck at worms include gray-crowned rosy finches, American pipits, common ravens, horned larks, semipalmated plovers and snow buntings. The loss of ice worms could trigger a cascade effect throughout the entire glacial food web.
When Glaciers Die, So Do Their Worms
Dial says Byron Glacier, like much of ice worms’ habitat, has shrunk dramatically in just one year. A warming Arctic could be the ice worms’ undoing. The rapid pace of glacial retreat isn’t giving ice worms time to adapt or find new homes.
On Sholes and, Ptarmigan Glacier our annual census is showing a significant decline, likely due to a more limited snowcover duration. As the snowcover on glaciers is limited in extent and duration that is stressful on ice worms leading to population declines. Field observations are confirming what scientists feared most.
But I think, you know, this idea that these are worms that only live on ice means that once the ice is gone, the ice worms will be gone. GROSS: So this creature, adapted to live in a frozen world, must now adapt to the thaw or, like the polar bear, face possible extinction. Unlike some species that might relocate or adapt, ice worms are truly trapped by their specialization.
The Final Countdown
Yet, time is running out. Unless an effort is made to reverse or lessen climate change’s damage, these worms may be lost to time. The ice worms’ story has become a race between scientific discovery and environmental destruction.
Ice worms, however, show that this fragile environment – where the glaciers are vulnerable to climate change and are retreating – is potentially far more complicated. “If you were going to put a biological mascot on glaciers of the Northwest,” Hotaling says, “it’s an ice worm.” These creatures have become unlikely symbols of what we stand to lose.
Our limited genetic evidence suggests that ice worms probably covered the landscape during the last glacial period,” Hotaling said. When the glaciers retreated at the end of the Pleistocene, around 20,000 years ago, the worms were left on isolated peaks, where they have thrived ever since. Now, however, even these last refuges are disappearing.
The story of Alaska’s ice worms serves as both a scientific marvel and a sobering warning. These remarkable creatures, perfectly adapted to their frozen world, are vanishing along with the glaciers they call home. As researchers race to unlock their secrets, the ice beneath our feet continues to melt. “If I think of my children, I am living in a world with maybe no glaciers. That’s actually quite alarming,” he told UN News.
What will happen when the last ice worm disappears into the mystery from which it came? Will we ever fully understand these extraordinary beings before they melt back into legend? What do you think we should do to preserve these ancient survivors of the ice age?
