Megan's Nature Nook
Nature Notes, Phenology, Photography, Fun Facts, Trips, Maybe Even a Bad Joke or Two... and More!
Winter and cold temperatures have finally hit us in Minnesota. Many birds (and some insects) migrate to escape the cold, other animals grow thick winter coats and adapt their diets to what is available, while others decide to skip the cold weather and just sleep through it. These tactics are all great ways to survive harsh winters, but did you know that some animals actually survive cold weather by freezing themselves and thawing out in the Spring? Usually freezing is not a good thing for living organisms - think frostbite. When ice forms, cells can be pierced by the growth of sharp ice crystals or the cell can rupture because of the expansion of fluids in the cell resulting in the death of the cell. Luckily some animals have special cryoprotectant (cryo = ice, cold, frost in Greek) substances in their tissue that protects the tissue from freezing and being damaged. Wood Frog Wood frogs (Lithobates sylvaticus) live in wooded areas and when cold weather approaches they bury themselves under leaf litter just under the surface of the soil. They can freeze up to 70% of their body including the brain and lenses of the eyes. Their heart completely stops, their breathing stops, and there is no muscle movement. Then in Spring when their body warms up, water will return to the cells and the frog returns to normal functions. They will repeat this process each year. How can they freeze and essentially cease to live for such a long time? Wood frogs have special nucleating proteins that suck most of the water out of their cells. The liver produces glucose (sugar) to fill the cells and prevents them from freezing solid and rupturing. This natural antifreeze protects their cells in cold weather. Woolly Bear Caterpillar Woolly Bear Caterpillars (Pyrrharctia isabella) are the larval stage of the Isabella Tiger Moth. These fuzzy black and brown caterpillars are usually seen in the fall as they search for their overwintering spots inside cavities, under leaves, rocks, logs, or bark. Their long “fur,” called setae, helps them to freeze more controllably. They produce a natural antifreeze called glycerol which keeps cells from fully freezing and bursting. Woolly Bear Caterpillars will spend winter in this mostly frozen state and will thaw in the Spring and make a cocoon, later emerging as a moth. These small yet mighty insects can survive down to -90°F! Painted Turtle Hatchling
Painted Turtles (Chrysemys picta) lay their eggs in early summer (June) and they hatch in late summer (August). Although many turtle hatchlings will emerge from the nest to start their new lives, some will overwinter as hatchlings underground in the nest. Environmental cues dictate whether the turtles should emerge or stay in the nest for winter. Painted Turtle hatchlings can do something called supercooling. They’re able to lower their body temperature to as low as 10°F without having their body fluids freeze. They’re able to do this because they don’t have Ice Nucleating Agents (INAs) internally. INAs are particles that an ice crystal can form around. So without INAs they can cool below freezing without ice forming and causing damage to the cells. It’s pretty amazing what each of these small creatures can do to survive our harsh winters! Animals have a variety of ways to help them survive winter, but I think freezing themselves and being able to thaw out in the spring is one of the most unique ways! As you bundle up to enjoy the great outdoors this winter, think of all the animal popsicles that may be hiding just out of sight awaiting the warmth of Spring.
2 Comments
Lonnie Hebl
1/12/2024 09:26:17 pm
Very interesting! Thanks for sharing. Lon
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Julie
1/13/2024 04:35:53 pm
Very interesting wonders of nature.
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