Pompeii worm

Pompeii worm
Scientific classification
Kingdom: Animalia Phylum: Annelida Class: Polychaeta Order: Terebellida Family: Alvinellidae Genus: Alvinella Species: A. pompejana
Binomial name
Alvinella pompejana Desbruyéres and Laubier, 1980

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.

Introduction

In 1997, nearly 21 years after the discovery of the first hydrothermal vent system, marine biologist Craig Cary and colleagues identified the most heat-tolerant animal on Earth—Alvinella pompejana, the Pompeii worm. Pompeii worms were initially discovered by French researchers in the early 1980s and are described as deep-sea polychaetes that reside in tubes near hydrothermal vents along the seafloor. They can reach up to 5 inches in length and are pale gray with red tentacle-like gills on their heads. Perhaps most fascinating, is that their tail end is often resting in temperatures as high as 176 °F (80 °C), while their feather-like head sticks out of the tubes into water that is a much cooler 72 °F (22 °C). Scientists are attempting to understand how Pompeii worms can withstand such extreme temperatures by studying the bacteria that form a "fleece-like" covering on their backs. Living in a symbiotic relationship, the worms secrete mucous from tiny glands on their backs to feed the bacteria, and in return they are protected by some degree of insulation. The bacteria have also been discovered to be chemolithotrophic, contributing to the ecology of the vent community.

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 150 °C.

Biology

Reaching a length of up to 13 centimeters (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.

Pompeii worms have a feather-shaped head. The plume of tentacle-like structures on it are gills, coloured red by haemoglobin.

Name

Pompeii worms get their name from the Roman city of Pompeii that was destroyed during an eruption of Mount Vesuvius in AD 79. Its 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.

Symbiotic bacteria

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—and by extension the worms—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.

Behavior

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.

Thought to subsist on vent microbes, the Pompeii worm pokes its head out of its tube home to feed and breathe. It is the posterior end that is exposed to extreme temperatures; the anterior end stays at a much more comfortable 22 °C (72 °F).

External links

• Exploratorium: The worm that boasts the world's hottest lifestyle
• Mission to the Abyss: includes an interactive 3D rendering of a Pompeii worm
• National Geographic article about the Pompeii worm

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