A tiny worm discovered in the Great Salt Lake could help scientists better understand the origins and resilience of life in extreme environments. Its story remains largely a mystery.
The Great Salt Lake is famous for brine shrimp, brine flies, and water so salty that few animals can survive in it. Now scientists have added a far stranger resident to that short list: a tiny worm that appears to live nowhere else on Earth.
Researchers at the University of Utah have formally described a new free-living nematode found in the lake’s microbialites, the reeflike mineral mounds that cover parts of the lakebed. The species, named Diplolaimelloides woaabi, measures less than 1.5 millimeters long (0.06 inches), but it could offer important clues about life in one of North America’s most extreme aquatic environments.
The name honors the Northwestern Band of the Shoshone Nation, whose ancestral lands include the lake. Michael Werner, an assistant professor of biology who led the research team, consulted tribal elders, who recommended Wo’aabi, an Indigenous word meaning “worm.”
A Tiny Animal Hidden in a Harsh Lake
Nematodes are among the most abundant animals on Earth. They live in soil, polar ice, deep ocean vents, and many other environments, and more than 250,000 species are known. Yet until 2022, none had been confirmed in the Great Salt Lake.
That changed when Julie Jung, then a postdoctoral researcher in Werner’s lab, found nematodes during sampling trips by kayak and bicycle. The worms were living in microbialites, hardened structures built by microbial communities that help support the lake’s food web.
“We thought that this was probably a new species of nematode from the beginning, but it took three years of additional work to taxonomically confirm that suspicion,” said Jung, now an assistant professor at Weber State University.
The team confirmed the species using 18S DNA sequencing and detailed anatomical studies with scanning electron microscopy and differential interference contrast (DIC) microscopy. Those methods revealed tiny but important features, including eyespots, fused lips, a funnel-shaped mouth cavity, short sensory bristles, and specialized male reproductive structures.
Only the Third Known Animal Group in the Lake’s Salty Water
The discovery makes nematodes only the third known metazoan animal group living in the Great Salt Lake’s hypersaline waters. The others are brine shrimp and brine flies, which help feed huge numbers of migratory birds.
Diplolaimelloides woaabi belongs to the family Monhysteridae and order Monhysterida, groups known for members that can tolerate salty or otherwise extreme habitats. Its genus is usually associated with coastal marine or brackish environments, making its presence in Utah especially puzzling. The Great Salt Lake sits about 4,200 feet above sea level and roughly 800 miles from the nearest ocean.
Researchers have also found genetic evidence that a second nematode species may live in the lake, though more study is needed.
“It’s hard to tell distinguishing characteristics, but genetically we can see that there are at least two populations out there,” Werner said.
How Did It Get There?
The worm’s origin is one of the biggest mysteries. One possibility reaches back to the Cretaceous Period, when a vast seaway divided North America and parts of present-day Utah bordered marine water. Co-author Byron Adams, a Brigham Young University biology professor and nematode expert, thinks the worms may be ancient survivors from that time.
“So we were on the beach here. This area was part of that seaway, and streams and rivers that drained into that beach would be great habitat for these kinds of organisms,” said Adams, who also has a nematode species named after him. “With the Colorado Plateau lifting up, you formed a great basin, and these animals were trapped here. That’s something that we have to test out and do more science on, but that’s my go-to. The null hypothesis is that they’re here because they’ve always kind of been here.”
That idea would mean the worms endured major changes in the region, including the freshwater Lake Bonneville, which covered northern Utah between 20,000 and 30,000 years ago.
“If the nematode has been endemic since 100 million years ago, it has survived through these dramatic shifts in salinity at least once, probably a few times,” Werner said.
Another possibility is that the worms arrived more recently on migratory birds, perhaps carried in feathers or mud from other saline lakes.
“So who knows. Maybe the birds are transporting small invertebrates, including nematodes, across huge distances,” Werner said. “Kind of hard to believe, but it seems like it has to be one of those two.”
A Possible Warning System for a Changing Lake
The worms appear closely tied to microbialites, where they live in algal mats and feed on bacteria. Researchers found them mainly in the upper few centimeters of the mats (roughly the top inch), but not deeper down.
That narrow habitat could make the species especially important. Microbialites help drive the lake’s biological productivity, so any animal that interacts with their microbial communities could influence the wider ecosystem.
The team also found a puzzling sex ratio. In wild samples, less than 1% of the worms were male. In lab cultures, males made up about half the population.
“That’s another confusing part of the story for us. When we sample out there on the lake and bring them back in the lab, we get less than 1% males. But when we have cultured them in the lab, the males make up about 50% of the sex ratio,” Werner said. “We’re super happy to be able to culture them in the lab, but there’s something about it that’s clearly different than the lake environment.”
Because nematodes often respond quickly to environmental stress, scientists use them as bioindicators of water quality, salinity, sediment chemistry, and ecosystem change. That could make Diplolaimelloides woaabi valuable as the Great Salt Lake faces pressure from drought, water diversion, shrinking lake levels, and rising salinity.
“When you only have a handful of species that can persist in environments like that, and they’re really sensitive to change, those serve as really good sentinel taxa,” Adams said. “They tell you how healthy is your ecosystem.”
For now, Diplolaimelloides woaabi is both a new species and a new mystery. It may be a relic of ancient seas, a traveler carried across continents by birds, or part of a hidden microbial world scientists are only beginning to understand.
Reference: “Diplolaimelloides woaabi sp. n. (Nematoda: Monhysteridae): A Novel Species of Free-Living Nematode from the Great Salt Lake, Utah” by Julie Jung, Thomas R. Murray, Morgan C. Marcue, Thomas Powers, Solinus Farrer, Abigail Borgmeier, Byron J. Adams, Jonathan A. Wang, Gustavo Fonseca and Michael S. Werner, 1 February 2025, Journal of Nematology.
DOI: 10.2478/jofnem-2025-0048
Funding for this research came from the National Institutes of Health, Society of Systematic Biologists, National Science Foundation and Conselho Nacional de Desenvolvimento Científico e Tecnológico.
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