Cryopreservation of nematode Caenorhabditis elegans in the adult stage

Cryopreservation of nematode Caenorhabditis elegans in the adult stage is of importance as the nematode is a powerful research model organism. In this study, we applied the protocol previously established for cryopreservation of the L4 nematode to the adult one, and achieved a survival rate of 84%. When ice seeding was induced with bacteria P. syringae directly added to the nematode suspension instead of using a pre-cooled steel sticking needle, comparable survival rate was obtained after thawing. Moreover, a simple freezing device composed of a polystyrene foam box surrounded by a Dewar vessel put in a deep freezer was developed for a practical use. This simple method obtained a survival rate of 69 ± 4% for the adult nematode after thawing.