TREONIS, A.M.*; WALL, D.H.; Creighton University; Colorado State University: Soil nematodes and desiccation survival in the extreme arid environment of the Antarctic Dry Valleys

Soil nematodes are capable of employing an anhydrobiotic survival strategy in response to adverse environmental conditions. The McMurdo Dry Valleys of Antarctica represent a unique environment for the study of anhydrobiosis because extremes of cold, salinity, and aridity combine to limit biological water availability in the rocky soils that cover most of the landscape. The coiled morphology of nematodes extracted from dry valley soils suggests that they employ anhydrobiosis, as do nematodes in hot desert soils. We studied nematode activity (use of anhydrobiosis) in the dry valleys over seasonal and diurnal temporal scales and in relation to environmental variables such as soil moisture, electrical conductivity, water potential, and temperature. Our data show that nematode coiling is most strongly correlated to soil moisture and varies slightly on a diurnal time scale, with more nematodes uncoiled at the warmest time of day. In the driest soils studied (gravimetric water content < 2%) more than 50% of nematodes extracted were found coiled. These nematodes showed enhanced survival from extreme desiccation when re-hydrated in water as compared to uncoiled nematodes. In the field, dry valley nematodes uncoiled rapidly (< 6h) in response to soil wetting. Nematode activity in the dry valleys appears to be significantly limited to time intervals following rare snowfall and melting events during the austral summer. Anhydrobiosis likely represents a significant temporal component of a nematode�s life span in the dry valleys.