Scientists Discover an Amoeba That Thrives at 63°C, Shattering the Heat Limit for Complex Life

When things get even hotter, it has another trick up its sleeve.

Most living things would have a very bad day in water heated to 63°C (145°F). For humans, it can cause severe burns in seconds. For most plants and animals, it’s simply too hot to survive.

But deep in the steaming hot springs of California, scientists have discovered a microscopic creature that seems to thrive in these temperatures. It eats, moves around, and even reproduces.

The newly discovered amoeba, named Incendiamoeba cascadensis, has set a new heat-tolerance record for eukaryotes — the enormous group of organisms that includes animals, plants, fungi, and many single-celled microbes. In fact, it can divide at temperatures previously considered beyond the limits of complex cellular life.

And when the heat becomes unbearable, this tiny organism has another remarkable survival strategy: it transforms itself into a protective capsule and waits for conditions to improve.

A tiny predator in boiling-hot territory

The discovery came from California’s Lassen Volcanic National Park, a landscape of steaming pools and geothermal streams.

Between 2023 and 2025, researchers collected samples from several of the park’s geothermal environments. The team, led by biologists at Syracuse University, wanted to investigate whether heat-loving amoebae could survive at temperatures previously thought impossible for organisms with complex cells.

One sample, collected from an unremarkable-looking tributary of Hot Springs Creek, contained something extraordinary.

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Back in the laboratory, the researchers identified a previously unknown amoeba. They named it Incendiamoeba cascadensis, which roughly translates to “fire amoeba from the Cascades.” The organism is a predator, feeding on bacteria that thrive in the same scorching environment. Its flexible body allows it to change shape, crawl across surfaces, and engulf its microscopic prey.

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But its most remarkable ability only became apparent when the researchers started turning up the heat.

A new record for complex life

The researchers initially grew the amoebae at 57°C, the previous upper temperature limit for amoeba growth. The organisms appeared perfectly comfortable.

So the team increased the temperature.

At 60°C, the amoebae continued to grow. At 63°C, they were still reproducing. At 64°C, it can still move around, although the researchers did not observe sustained reproduction at that temperature.

The amoeba doesn’t just love heat; it seems to require it. The organism could not grow at 40°C or below in the laboratory, meaning that conditions we would consider dangerously hot are essential for its normal life cycle.

When it gets too hot, it transforms

The amoeba has one more trick up its sleeve: a transformation.

As temperatures climb beyond its preferred range, the organism becomes less active. Eventually, it changes shape and forms a protective outer layer, entering a dormant state called a cyst. This allows it to endure conditions that would otherwise destroy its cellular machinery.

In laboratory experiments, the amoebae recovered after five minutes of exposure to 70°C. Once returned to cooler conditions, they could resume their normal activities.

However, exposure to 80°C proved too much: the organisms failed to recover.

Could there be even tougher organisms out there?

If all this time we had no idea there’s an amoeba capable of reproducing at 63°C, what else might be hiding in Earth’s hottest environments?

The researchers found related DNA sequences in existing environmental samples from geothermal areas, including Yellowstone National Park and New Zealand. This suggests that other heat-loving amoebae may be more widespread than previously recognised.

Finding such resilient creatures could be important. Understanding how they protect their proteins could eventually help scientists develop heat-resistant enzymes for industrial processes. Furthermore, the discovery has implications beyond Earth.

Researchers studying the possibility of extraterrestrial life need to understand the environmental conditions that living cells can tolerate. The fire amoeba demonstrates that organisms with complex cells can remain active at temperatures exceeding previously established limits.

Of course, surviving extreme heat is only one part of the equation. Life also requires suitable chemical conditions, nutrients, water, and other essential resources. The discovery does not establish that complex life exists elsewhere in the universe.

Still, the fire amoeba offers a reminder that the limits of life are not always where we expect them to be.

Journal Reference: Rappaport et al., A geothermal amoeba sets a new upper temperature limit for eukaryotes, published in Cell on September 22, 2026.