Cryozoa are organisms capable of surviving temperatures below 0°C for extended periods. Sperm and bacterial cultures are routinely preserved in liquid nitrogen at -196°C, while the nematode Panagrolaimus davidi can survive freezing of all of its body water. Other organisms such as some frogs, turtles and snakes may freeze their extracellular water to safeguard their cells during low temperatures and make use of antifreeze proteins. Cryozoa include cryophiles, which not only survive low temperatures, but are capable of growth and reproduction in such conditions.