SURVIVAL OF INTRACELLULAR FREEZING BY THE ANTARCTIC NEMATODE PANAGROLAIMUS-DAVIDI

Animals are usually thought to survive ice formation in their bodies o nly if the ice is confined to the body cavity and to extracellular spa ces. Intracellular ice formation is believed to be fatal. This conclus ion is based on studies of the cryopreservation of mammalian cells. In tracellular freezing has been observed in some living insect cells but has not been observed in intact animals. Nematodes are transparent an d so the location of ice in their bodies can be observed directly usin g a cryomicroscope stage. We have observed freezing and melting in all body compartments, including intracellular compartments, of the Antar ctic nematode Paraagrolaimus davidi. Inoculative freezing from the sur rounding water occurs via the body openings, rather than across the cu ticle; most frequently it occurs via the excretory pore. Individual ne matodes that have frozen intracellularly will subsequently grow and re produce in culture. Determining the mechanisms by which this nematode survives intracellular freezing could have important applications in t he cryopreservation of a variety of biological materials.