Matthias Bittenbinder
Yesterday at 10.30pm
Winter made itself felt for a moment. Those cold days when the sun shines are beautiful. I haven’t ventured into skating yet, as far as I’m concerned it needs to gel a little more convincingly.
Most animals look for a place to hibernate before the winter months arrive. Frogs, for example, spend the winter in mud or under leaves at the bottom of lakes, swamps or in a garden pond.
These places offer excellent protection against the freezing cold. Other species seek refuge on land, for example under stones, tree stumps or in leaf litter.
However, there are also species of frogs that do not fear the winter cold. Let’s take the wood frog, a species that looks very similar to the “normal” brown frog that we also find in the Netherlands, but which has a strange make-up. This frog lives in Canada and the northern United States and is the only frog found above the Arctic Circle.
One of the most notable properties of this animal is its ability to freeze alive. The frog does this by using a kind of natural antifreeze, which is found in its blood. This antifreeze is glucose – a type of sugar – which prevents the water in the frog’s cells from freezing.
When it begins to freeze, these high sugar concentrations prevent ice crystals from forming in the frog’s cells. Sugar only freezes at much lower temperatures than water.
The result is that the water in the blood is frozen, but the cells are protected. Normally, the formation of sharp ice crystals would damage cells, causing them to die. The wood frog’s ability to prevent ice formation keeps the frog’s cells intact.
During this period of frost the tree frog’s vital functions practically stop. The heartbeat stops, breathing largely stops, and the frog no longer shows any signs of life. In this way the frogs can survive temperatures of more than 10 degrees below zero. When spring arrives and the temperature starts to rise again, the frog slowly melts and then jumps as if nothing had happened. They often look for a partner immediately after thawing, probably to warm up further.
The ability to freeze alive has helped the wood frog survive extreme winters without problems. This fascinating survival strategy has not escaped scientists. By studying these frogs they have acquired valuable knowledge that can be applied, for example, in the field of organ transplants.
By better understanding how these frogs freeze, we may be able to use similar antifreeze in the future to transport donor organs more safely or store them for longer. Not bad for such a beautiful frog.
Mátyás Bittenbinder is a biologist, presenter and writer. He is a biologist at Naturalis and VU Amsterdam. Instagram: matyasbittenbinder
2024-01-13 21:30:00
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