Pompeii worm

The Pompeii worm (Alvinella pompejana) is a deep-sea polychaete vermiform extremophile found only at hydrothermal vents in the Pacific Ocean, discovered in the early 1980s off the Galápagos Islands by French researchers.

Pompeii worms get their name from the Roman city of Pompeii that was destroyed during an eruption of Mount Vesuvius in AD 79. Attaching themselves to black smokers, the worms have been found to thrive at temperatures of up to 80°C (176°F), making the Pompeii worm the most heat-tolerant complex animal known to science after the tardigrades or water bears, which are able to survive temperatures over 150ºC.

Pompeii worms simultaneously keep their heads (including the gills) in much cooler water while their tails are exposed to hot water (see below). Since their internal temperature has yet to be measured, it is plausible that a Pompeii worm survives exposure to hot water by dissipating heat through its head to keep its internal temperature within the realm previously known to be compatible with animal survival.

The Pompeii worm's family name Alvinellidae and genus name Alvinella both derive from DSV Alvin, the three-person submersible vehicle used during the discovery of hydrothermal vents and their fauna during the late 1970s. The family Alvinellidae contains eight other species, but none match the Pompeii worm's heat tolerance.

Reaching a length of up to 13 centimetres (5 inches), Pompeii worms are a pale grey with "hairy" backs; these "hairs" are actually colonies of bacteria which are thought to afford the worm some degree of insulation. Glands on the worm's back secrete a mucus which the bacteria feed on (see symbiosis). The Pompeii worms form large aggregate colonies enclosed in delicate, paper-thin tubes.

Thought to subsist on vent microbes, the Pompeii worm pokes its feather-like head out of its tube home to feed and breathe. The plume of tentacle-like structures on the head are gills, coloured red by haemoglobin. It is the posterior end that is exposed to extreme temperatures; the anterior end stays at a much more comfortable 22°C (72°F).

While it is not yet known precisely how the Pompeii worm survives these severe vent conditions, scientists suspect the answer lies in the fleece-like bacteria on the worm's back; this layer may be up to a centimetre thick. The bacteria may possess special proteins, "eurythermal enzymes", providing the bacteria&mdash;and by extension the worms&mdash;protection from a wide range of temperatures. It is plausible that the bacteria also provide thermal insulation. Studies are hampered by the difficulties of sampling; to date, Pompeii worms have not survived decompression.

Study of the Pompeii worm's seemingly life-sustaining bacteria could lead to significant advances in the biochemical, pharmaceutical, textile, paper and detergent industries.