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thumb|M. solifugus on [[Nisqually Glacier, Mount Rainier]]

Mesenchytraeus solifugus, commonly called an ice worm, is a species of oligochaete worm that inhabits coastal glaciers in northwestern North America. M. solifugus is dark brown and grows to about 15 mm long and 0.5 mm wide. It has a high population density and is common in suitable habitat. It can only survive at temperatures of approximately –7 °C to 5 °C. The ice worm is studied for its ability to survive in low temperatures. It has heavy pigment, absorbing most colors; however, it burrows into the glacier to avoid strong sunlight.

History and taxonomy

This species was first reported from Muir Glacier in Alaska. Carlo Emery named it solifugus in 1898, meaning "fleeing from the sun". Phylogeny suggests that it evolved from an aquatic ancestor. Adult ice worms are approximately long. However, the worms lack eyes or eyespots. Not much is known about the ice worm's diet, but it is thought to eat snow algae, as well as some bacteria.

Habitat

Ice worms inhabit glaciers and can be found in snowfields, avalanche cones, and glacier rivers and pools. The organisms require permanent glacial environments for survival and reproduction.

As well as the northwestern United States, ice worms have been found in glaciers of southern Alaska and certain parts of British Columbia. Though they are found in snowfields, rivers and pools, they are not found on dirty snow or rock. They freeze at around −6.8 °C (19.8 °F), and their bodies decompose after continuous exposure to temperatures above 5 °C (41 °F). This decomposition process, known as autolysis, occurs when the cells produce digestive enzymes and self-destruct. The body, figuratively, melts.

Even if other places are equally cold, ice worms never venture onto any other terrain. They eat the abundant snow algae and pollen carried by the wind.

Ice worms are most active in late spring. The snowfall provides insulation, and the temperatures below remains a stable 0 C (32 °F). Ice worms can still find plenty of algae in the firn layer, the layer of packed snow in transition to ice.

In glacial ponds or small streams, ice worms can be found in broad daylight. The freezing water provides the worms with a comfortable temperature, countering any heating of their dark bodies from the sun. In fast-flowing glacial streams, ice worms cling to the ice surface.

References

Sources

  • Hartzell, P. (2003). Glacial Ecology: North Cascades Glacier Macroinvertebrates. Retrieved on Oct. 21, 2005, from: https://web.archive.org/web/20051212000121/http://nichols.edu/departments/Glacier/bio/index.htm
  • Pelto, M. S. (2003). Ice Worms (Mesenchytraeus solifugus) and Their Habitats on North Cascade Glaciers. A study by North Cascade Glacier Climate Project. Retrieved on Sept. 28, 2005, from https://web.archive.org/web/20090209012557/http://www.nichols.edu/departments/glacier/iceworm.htm
  • Shain, D. H., Carter M. R., Murray, K. P., Maleski, K. A., Smith, N. R., McBride, T. R., et al. (2000). Morphologic Characterization of the Ice Worm Mesenchytraeus solifugus. Journal of Morphology, 246, 192-197.
  • Shain, D. H., Mason, T. A., Farrell, A. H., & Michalewicz, L. A. (2001). Distribution and behavior of ice worms (Mesenchytraeus solifugus) in south-central Alaska. Canadian Journal of Zoology, 79, 10, 1813-1821.
  • Dr. Daniel H. Shain @ Rutgers University
  • North Cascade Glaciers ice worms research
  • World Glacier Biology Program @ Clark University
  • Jason Project XIII 2001-2002
  • The Ballad of the Ice-Worm Cocktail by Robert W. Service @ U.S. Geological Survey