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

Abstract

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 western-most extent of known ice worm habitation. All ice worms identified in this study inhabit coastal glaciers proximal to the Gulf of Alaska. They were found in a variety of habitats including level snowfields, steep avalanche cones, crevasse walls, glacial rivers and pools, and hard glacier ice. Ice worms were not found on all coastal glaciers nor were they found in Alaska's interior (the Alaska Range). Ice worms on Byron Glacier, Alaska, totaled ~30 million and were distributed on seven distinct avalanche cones. They displayed a diurnal cycle, appearing on the glacier surface several hours before sunset and penetrating back into the glacier shortly after sunrise. Experiments suggest that ice worms preferentially penetrate the glacier beneath surface algae, Chlamydomonas nivalis, to a depth between 15 and 100 cm and resurface at a proximal location. Lateral movement of ice worms on the glacier surface can reach speeds of ~3 m/h. Ice worms on Byron Glacier avoided light, but did not respond preferentially to different wavelengths in the visible spectrum. Finally, ice worms displayed an unexpected attraction to heat.