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The Antarctic fellfield habitat is an extreme terrestrial environment in which the survival of organisms depends upon an ability to withstand both very low temperatures and severe water shortage. The potential to survive desiccation by entering a state of anhydrobiosis, and the conditions necessary to induce this state, were investigated in two species of free-living nematodes: Teratocephalus tilbrooki which inhabits the relatively sheltered environment of a moss cushion; and Ditylenchus sp. B, which lives in the more exposed aerial thalli of a lichen. Teratocephalus exhibits seasonal variation in the length of time it can survive anhydrobiotically. There is no evidence of increased resistance to water loss, which correlates with increased survival in this species. The ability of Ditylenchus to resist water loss and to survive anhydrobiotically is greater than Teratocephalus, with slower rates of water loss enhancing survival and, in addition, altering the shape of the survivorship curve by promoting survival during the initial period of anhydrobiosis. Whilst rates of water loss increase at higher temperatures, the subsequent survival of Ditylenchus reaches a maximum at 10-16°C. Once this species has been dehydrated high temperatures may be deleterious to its survival. However, once in the anhydrobiotic state temperatures as low as -80°C can be withstood. Cuticular resistance to water loss decreases with the time for which Ditylenchus has been rehydrated, but no similar changes are observed in Teratocephalus. Both species possess extremely well developed anhydrobiotic capabilities and are capable of surviving the levels of water stress recorded in their respective habitats within the maritime Antarctic.
Oikos © 1991 Nordic Society Oikos