By Dan Zarlenga, Missouri Department of Conservation
We’ve seen the science fiction movies, the ones where the astronauts embark on a many-year mission through the galaxy. The travelers put themselves in a “cryochamber” and—using incredible technology—slip into suspended animation. Time and aging stop for them as they sleep their long voyage away.
In nature, cryogenic sleep is not exotic science fiction—for some animals, it’s just how they spend the winter. One of those critters is even commonly found around here, the boreal chorus frog. In fact, they should be entering their long sleep just about now.
The journey the chorus frog must make is not from one star to another, but from one season to the next. Rather than the cold blackness of space, it must survive the cold and gray of a long winter.
We know the boreal chorus frog (formerly called the western chorus frog) by its familiar calls, heard during spring courtship. The frogs may only be an inch or so long, but the voices of the males sound off most conspicuously around ponds and streams as they attempt to attract mates. The call is like a raspy, vibrating trill, often described as a lot like a fingernail running over the teeth of a comb. But this time of year, they busy themselves with the task of survival.
The depths of winter offer nothing in terms of food and subsistence for these frogs, much like the starry void for long-distance space travelers. So boreal chorus frogs enter their own form of suspended animation. They burrow into shallow mud, a natural “cryochamber”. Instincts command their amphibian hearts to come to a stop, breathing ceases, metabolism slows, and they literally freeze.
Normally, ice crystals forming in the frog’s delicate tissues would be fatal to it. But these deep freeze dynamos secret miraculous protein crystals that act sort of like “decoy” cells. Ice forms around these crystals, instead of other more vital cells within the frog’s body. The frog can now freeze itself safely, without any damage. These protein crystals even contain their own antifreeze chemicals that prevent the crystals themselves from freezing.
The spacefarers of science fiction slumber through the depths of space until reaching the new worlds of their destination star. Thanks to an amazing natural adaptation, boreal chorus frogs journey the long, dark months of winter, until the light and warmth of our own star thaws them out again. They reawaken in a new world of spring.
Next time you watch a space travel movie, remember that the humble boreal chorus frog has been using its own form of suspended animation long before humans ever conceived of it. These amazing amphibians prove that realty can be more fascinating than fiction!