Abstract

Nematodes are found in almost all environments, including those where they are often exposed to extreme environmental stress. Panagrolaimus davidi is an Antarctic nematode living associated with moss and algae in terrestrial habitats on the Victoria Land coast that are free of snow and ice for part of the year. It has to survive very variable thermal and hydric environments where liquid water and temperatures suitable for growth are only periodically available. P. davidi can survive complete water loss (anhydrobiosis) and is the only organism that has been shown to survive intracellular ice formation throughout its tissues. It has several cold tolerance strategies, including; freeze avoidance, cryoprotective dehydration, freezing tolerance and anhydrobiosis. The mechanisms involved may include the production of trehalose, ice active proteins and the control of ice nucleation. Do the different survival strategies of P. davidi represent the expression of different gene sets or does the production of stress-related compounds provide protection against a variety of environmental challenges? Other nematodes, including Caenorhabditis elegans, are not so resistant to desiccation and freezing. Comparing the genomes of P. davidi and C. elegans may thus highlight the adaptations that are necessary for the survival of extreme environmental stress.