Ice worm refers to any of a number of species of worm that live in glacial ice, such as Mesenchytraeus solifugus, M. harrimani, M. kuril, M. maculatus, and M. obscurus.

The first ice worm species were discovered in 1887 in Alaska, on the Muir Glacier. These glacier ice worms can be found on glaciers in Alaska, Washington, Oregon and British Columbia. They have not been found in other glaciated regions of the world. The name "solifugus" is Latin for "sun-avoiding", as ice worms retreat underneath the ice before dawn. Enzymes in ice worms have very low optimal temperatures, and can be denatured at even a few degrees above 0°C. When ice worms are exposed to temperatures as low as 5°C, their membrane structures disassociate and fall apart (i.e., "melt") causing the worm itself to "liquify". Ice worms are several centimeters long, and can be black, blue, or white in color. The ice worms come to the surface of the glaciers in the evening and morning. On Suiattle glacier in the North Cascades population counts indicated over 7 billion ice worms on that glacier alone.

It is not known how ice worms tunnel through the ice. Some scientists believe they travel through microscopic fissures in ice sheets, while others believe they secrete some chemical which can melt ice by lowering its freezing point, like an antifreeze. They feed on snow algae.

In 1997, methane clathrate deposits in the ocean floor were found to be inhabited by a specialized worm of the class polychaete. The worms were given a species name, Hesiocaeca methanicola, and are often called Methane Ice Worms.

Ice worms in culture

Scottish-born Canadian poet of the Yukon Robert W. Service wrote a poem, "Ballad of the Ice-worm Cocktail", in which a fake ice worm made of spaghetti is the subject of a bar bet. This may have contributed to the impression that ice worms are mythical creatures.

Science fiction author Alastair Reynolds made ice worms the subject of his short story Glacial in a collection titled Galactic North. While the ice worms themselves are stupid, deterministic biological machines, the chemical trails they leave through the ice act as behavior-modifying signals for subsequent ice worms, creating a vast, if exceedingly slow, neural network in the pervasive glacial covering of an alien planet. Reynolds specifically compares the ice worm analogues in his story to terrestrial ice worms, in particular referencing a small pore just above their mouths which secretes salts to help them burrow through ice (see Road salt). Note that the behavior of the ice worms in this story is very similar to the computer simulation Langton's Ant, which demonstrates the potential complexity of emergent systems when following very simple rules.

Science fiction author Peter F Hamilton also used ice worms in his novel Fallen Dragon. An alien planet named Amethi has succumbed to "iso-lock," a permanent ice age in which even the atmosphere has frozen, and the emerging biosphere on the planet has essentially died. The planet is discovered by humans and seeded with artificial life forms phenotypically very similar to ice worms. The distinguishing characteristic of these worms is that, while they chew through the ice and organic material of the dead planet, they excrete terrestrial bacteria as a first step in terraforming the planet to make it suitable for human habitation.

The small town of Cordova, Alaska has an annual Ice Worm Festival in February, in which a long imitation ice worm is paraded through the streets rather like a Chinese new year dragon dance.

External links

• Scientists Discover Methane Ice Worms on Gulf of Mexico Sea Floor
• North Cascade Glaciers ice worms research
• Ballad of the Ice-worm Cocktail
• Cordova Ice Worm Festival
• Seattle Times Article on Iceworms