https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0086807This article talks about the extreme cold-tolerance of Ozobranchus jantseanus, a leech of freshwater turtles.
This leech can survive being frozen in liquid nitrogen (-320.8° F, or -196°C) for 24 hours. It can withstand warmer ridiculously cold temperatures for many months! It can withstand repeated freezes and thaws, with similar temperatures, too.
leech_