Mesenchytraeus solifugus

Mesenchytraeus solifugus is a species of oligochaete worms commonly called ice worms that inhabits coastal glaciers in the North Western portion of North America. M. solifugus is dark brown and grows to about 15 mm long and 0.5 mm wide. They have a high population density and are relatively common in their area. The ice worms are also very sensitive to temperature and can only survive from approximately -7 °C to 5 °C. The ice worm is studied for it’s ability to survive in low temperatures. Ice worms have heavy pigment, absorbing all colors or reflecting dark brown; however, they burrow into glaciers to avoid strong sunlight. Carlo Emery named the species "solifugus" in 1898, meaning "fleeing from the sun".
Taxonomy.
"Mesenchytraeus solifugus" also known as ice worms or ice-worms are annelids. Ice worms were first reported on Muir Glacier in Alaska. Solifugus means "sun avoider" which can describe their behavior in different aspects of sunlight. Phylogeny suggests that they evolved from an aquatic ancestor due to the other members in the order.
Description.
Ice worms are predominantly small and are the only known psychrophilic annelids. Adult ice worms are approximately 1.5- 2.5 cm in length. They live their entire lives in snow or ice. Dark in color, usually a dark-brown or black, the ice worm’s color is thought to be an adaptation that helps protect it from radiation on the glacier. Their fluid and flexible body are able to squeeze through air holes and tiny crevasses in ice.It is believed that the ice worm has a lifespan of five to ten years.
Ice worms have an elongated head pore, multiple sensing organs which are located on their prostomium and ventral surface. These organs are responsible for chemo-, thermo, and photorecpetion. However, they do however lack eyes or eyespots. They also have setae that are differentiated from other related organisms because they curve at the end. All of these structures may aid the organism in its ability to survive in glacial environments. 
Little is known about the life cycle of the ice worm; it is thought to be unusually slow. It requires temperatures of 0°C for a successful reproduction. Cocoons are dispersed by birds. Ice worms cannot leave where they are. Not much is known about the ice worm's diet, but it is thought that it eats snow algae as well as some bacteria.
Habitat.
Ice worms have evolved a mechanism for surviving on snow and glacial ice. Ice worms can be found west of North America. They inhabit glaciers and can be found in snowfields, avalanche cones, and glacier rivers and pools. These environments have freezing-point temperatures and are nutrient poor. The organisms require permanent glacial environments for survival and reproduction.
Ice worms have also been found in glaciers in southern Alaska and in certain parts of British Columbia. They are very abundant (about 100 per sq m). Though they are found in snowfields rivers and pools, populations are never found near dirty snow or rock.
Behavior.
The ice worms display a diurnal cycle by appearing on the glacier's surfaces before sunset, and entering back into the glacier when the sun rises. It has been shown that they enter back into the glacier beneath the surface algae. They are extremely active in late spring. Light levels determine the movements of these organisms. Like other oligochaetes that avoid strong radiation and are attracted to dim light, this may explain their behavior for rising before the sunsets. Their pigment is what helps protect them from radiation.
Ice worms increase their energy levels as temperatures decrease, and tend to become lethargic as temperatures rise. They “melt” at room temperatures, which is caused by the liquefaction of their membranes. Ice worms are most active at 0°C. They freeze at a temperature of -6.8°C and self destruct at a continuous temperature of 5°C. Their metabolisms have adapted to cold temperatures.They can penetrate the glacier burrowing several feet down until they reach an area that is temperature favorable.
They move on the surface of ice at 3m/h and get through snow by moving through the grains.Lateral movement is usually along the surface of the glacier and they penetrate the glacier vertically. They have also been known to anchor themselves in glacial ice during times of runoff.
Ecology.
"Mesenchytraeus solifugus" have a very narrow acceptable temperature range. Ice worms 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.
They are the only known worm to spend their entire life in temperatures near 0 C (32 °F). 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.
In the summer, ice worms follow a diurnal cycle—at the first light in the morning, they sink into the glacier. A few hours before sunset, they poke out from the snow.
Ice worms can still be found in broad daylight. Many of them gather in glacial ponds or small streams. Scientists believe the water blocks out the sun's longer wavelengths which the worms avoid, and the freezing water provides the worms with a comfortable temperature.
In fast-flowing glacial streams, ice worms cling onto the icy surface. Researchers have observed the worms gyrate their head in the stream, possibly catching algae and pollen carried by the water. In still ponds, ice worms gather in bundles. Researchers speculate this has something to do with their reproduction. Ice worms do not graze in groups on the surface. The bonding in the still pond provides the rare opportunity for breeding.
Since in the winter the surface temperature on a glacier could reach −40 C (−40 °F), scientists doubt the worms follow the diurnal pattern. The worms most likely remain below the surface. The snowfall provides insulation and the temperatures below maintain 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. Scientists know little about the ice worm during the winter as the inaccessibility of glaciers prevents further study.
Medical uses.
Researchers are now investigating what prevents the worm from freezing at 0 C (32 °F) and are looking at the evolutionary steps by which the ice worm diverged from other species. Understanding the ice worm's secret could help preserve vital organs for transplant, and could aid in the understanding of potential extraterrestrial life on cold planets, as well as species on Earth which survive in climates colder than previously thought possible.
Scientific studies.
Ice worms produce increasing amounts of adenosine triphosphate(ATP) as the temperature in their environment drops. This adaptation is how they are above to survive in glacier ice. Respiratory rates generally decrease as temperature decreases. For most organisms exposure to temperatures of 0 degrees Celsius causes their metabolic rates to fail and for cells to not function properly.
Antifreeze proteins of ice worms are studied for surgeries where organs have to be kept cold. Funded by NASA and NIH for research purposes.