15. Devil Worm (Halicephalobus mephisto)
The devil worm, Halicephalobus mephisto, is a nematode species discovered nearly two miles beneath the Earth’s surface in South African gold mines. (nationalgeographic.com) It thrives in subterranean aquifers with temperatures up to 48°C (118°F) and oxygen levels less than 1% of those at the surface. (en.wikipedia.org) This adaptation is facilitated by an expanded repertoire of heat-shock proteins, particularly Hsp70, which help refold damaged proteins under heat stress. (nature.com) (aura.american.edu) (american.edu) (nationalgeographic.com)