Some worms like it hot.

The Pompeii worm (Alvinella pompejana) is an extremophile—an animal that thrives under extreme conditions. It makes its home at the top of hydrothermal vent “chimneys,” where superheated water belches from within the Earth’s crust, delivering a rain of mineral “ash.” Here, large numbers of worms live side by side, each darting in and out of their paper-thin tubes while waving pointy, rust-colored gills.

Pompeii worms build their tubes directly on the rocky vent chimneys. The base of these dwellings can experience temperatures up to 105 degrees Celsius (221 degrees Fahrenheit) hot, and the inside of the tube isn’t much cooler either.

What’s the secret to surviving such scalding temperatures? The woolly worm scuttles back and forth between the hot water rich in nutrients and the cool water rich in oxygen—movement that also mixes cool water into the tube. But more importantly, a fleece-like layer of bacteria helps insulate the Pompeii worm from the extreme heat.

On its own, a Pompeii worm can only tolerate temperatures up to 55 degrees Celsius (131 degrees Fahrenheit), but their bacterial coating redistributes the heat to keep the worm cool. The bacteria not only help regulate the temperature of the worm, they also break down minerals from the vent to aid their host.

Video observations captured by MBARI’s remotely operated vehicles (ROVs) in the Gulf of California illuminate the behavior of these worms in their natural environment. MBARI researchers are also leveraging genetics to learn how one population is connected to another from vent to vent. We have sequenced samples from Pompeii worms all along the East Pacific Rise—a mid-ocean ridge that stretches from Mexico to Easter Island—and the Pacific Antarctic Ridge further south.