Halicephalobus mephisto is resistant to a temperature as high as 37 °C (higher than most terrestrial nematodes can tolerate),[1] it reproduces asexually, and feeds on subterranean bacteria. According to radiocarbon dating, these worms live in groundwater that is 3,000–12,000 years old.[2] The worms are also able to survive in waters with extremely low levels of oxygen, lower than one percent of the level of most oceans.[2] It is named after Mephistopheles, the Lord of the Underworld in the Faust story,[2] and alludes to the fact it is found so deep under the Earth's surface.[1]