Central Ideas (main idea)

The Pompeii worm (Alvinella pompejana), a polychaete residing on the walls of deep-sea hydrothermal vents, experiences one of the steepest temperature gradients of any known animal: its tail rests in vent fluid reaching 80°C, while its head protrudes into 22°C seawater. Biologist Craig Cary observed that the worm's dorsal surface is covered in a thick layer of episymbiotic bacteria. Through in situ measurements, Cary found that this bacterial "fleece" functions as an insulating thermal barrier, reducing the temperature at the worm's skin by as much as 20°C compared to the surrounding vent fluid, thereby allowing the worm to inhabit a microenvironment that would otherwise be biochemically intolerable.