Distribution and behavior of ice worms (Mesenchytraeus solifugus) in south-central Alaska

The ice worm, Mesenchytraeus solifugus ssp. rainierensis, is the only known annelid that survives in glacier ice. We report the locations of eight ice worm populations in south-central Alaska, including the northern- and west ern-most extent of known ice worm habitation. All ice worms identified in t his study inhabit coastal glaciers proximal to the Gulf of Alaska. They wer e found in a variety of habitats including level snowfields, steep avalanch e cones, crevasse walls, glacial rivers and pools, and hard glacier ice. Ic e worms were not found on all coastal glaciers nor were they found in Alask a's interior (the Alaska Range). Ice worms on Byron Glacier, Alaska, totale d similar to 30 million and were distributed on seven distinct avalanche co nes. They displayed a diurnal cycle, appearing on the glacier surface sever al hours before sunset and penetrating back into the glacier shortly after sunrise. Experiments suggest that ice worms preferentially penetrate the gl acier beneath surface algae, Chlamydomonas nivalis, to a depth between 15 a nd 100 cm and resurface at a proximal location. Lateral movement of ice wor ms on the glacier surface can reach speeds of similar to3 m/h. Ice worms on Byron Glacier avoided light, but did not respond preferentially to differe nt wavelengths in the visible spectrum. Finally, ice worms displayed an une xpected attraction to heat.