Paralvinella sulfincola is a species of polychaete worm of the Alvinellidae family that thrives on undersea hot-water vents. It dwells within tubes in waters surrounding hydrothermal vents, in close proximity to super-heated fluids reaching over 300 °C. The upper thermal limit for this polychaete is unknown; however, it is unlikely they can survive in constant temperatures over 50 °C. It may tentatively be named a metazoan extremophile or, more specifically, a thermophile.