I understand freezing cells will cause cells to rupture because water expands upon freezing. That said:
How do they successfully freeze sperm and eggs, for example?
And, related to this, my trees have loads of bagworms and praying mantis’ chrysalises* waiting for spring. How do these eggs survive the winter (especially with subfreezing temps)?
Last, how do plant cells survive the winter? Sure, the sap in trees runs into the roots, but I have rose bush canes that stay dark green in the winter. If dead, one would expect these to become woody stems. But, this is not observed. How do these cells survive the harsh winter?
*technically, these so-called chrysalises are really oo…something?
Here’s why freezing and thawing eggs is so difficult. The human egg is a huge cell full of water, and when that water freezes, it forms sharp crystals that can puncture the cell. Chromosomes are also stretched in a vulnerable spindle formation in eggs, instead of being wound tight like in normal cells. That makes for a fragile combination.
Cryopreservation has gotten better at protecting those delicate structures, especially as a flash-freezing process called vitrification has largely replaced slow-freezing. But it’s still as much art as science. “Even if fertility clinics have many technicians, they don’t trust everyone with egg freezing and thawing,” says Vitaly Kushnir, a fertility doctor at the Center for Human Reproductive in New York. “They only trust the best one.”
Just because it’s below freezing where you are doesn’t mean the organisms go below freezing, and even if they do they don’t necessarily go below freezing for sap and body fluids, but to survive even lower temperatures animals need countermeasures like higher concentrations of solutes, e.g.:
Plants that can survive the winter typically have a cell structure that gives the water someplace to go when it expands and freezes. Often the water inside the cell is pumped out into spaces in between the cells that exist specifically to allow the plant to freeze. This brings along its own problems since the water can then be carried away causing dehydration, which some plants (evergreens and shrubs for example) solve by having waxy leaves that help to prevent water loss.
Animals that can survive freezing typically use the glucose (or some other sugar) anti-freeze trick that was already mentioned, though others use a slightly different trick with certain proteins that control where the ice forms in their bodies so that they can protect vital structures from cell damage.
Alligators and crocodiles take a different approach. They stick their snout above the water and then just let the pond or lake that they are in freeze around them. Their metabolism slows down quite a bit (and these are animals that can go a long time without eating anyway, that’s part of the reason they survived the extinction event that killed the dinosaurs), so they won’t starve to death while frozen, but their metabolism doesn’t stop (they don’t freeze solid) and they do need to breathe, if slowly, which is why they stick their snout above the surface of the water/ice.
Correct if I am wrong. I thought only alligators did well in the cold and crocodiles did NOT. Which is why alligators have spread as far north as the Carolinas in the US and crocodiles have been confined to southern Florida.