Freezing hardiness in ectotherms has often been separated into two categories, freezing tolerance and freezing susceptibility. But more complex classifications have also been proposed. Helix aspersa hibernates in Brittany during winter. It has a high temperature of crystallisation (between -1.2( and -7.4 degrees C) and survives only few hours at freezing temperatures. Helix aspersa is a large snail, which needs a long time to freeze and can bear some ice formation in its tissues up to 60% of its total body water. It may be provisionally considered as a partially freezing tolerant species.
