Winter is fast approaching. The days are getting noticeably shorter, you can see your breath when you’re outside, and everyday you find yourself wondering if it’s too early to start listening to the Michael Buble Christmas album. Soon people will be reaching for their down coats, wool mitts, and knitted toques. But for some animals, they don’t need to worry about keeping warm when the temperature drops.
We were curious to see how certain invertebrates respond to the cold. So this week, we chilled in the lab with marine and terrestrial isopods. Ok, so the isopods did a bit more of the chilling than us. We set up two experiments. One measuring chill coma recovery following an ice bath, and one measuring supercooling point and survival following freezing.
A chill coma is a coma-like state brought on by cold temperatures. Everyone has experienced having cold hands outdoors. Sometimes, when it’s really cold your fingers become a bit stiff and difficult to move. That’s chill coma! As your hands warm-up, the movement in your fingers begins to return. When you hands feel normal again, that’s chill coma recovery. We measured chill coma recovery in isopods by putting individuals in test tubes sitting in cups filled with ice. After either 2, 5, 10, or 15 minutes in the ice, we took the isopods out and placed them on their backs in Petri dishes. Recovery was measured as the time it took for them to flip back over.
Supercooling is the process of cooling a liquid or gas below its freezing point, without it becoming a solid. You may be wondering, how is this possible? One way this can be achieved is with the use of cryoprotectants. Cryoprotectants are special substances produced in the blood that protect the tissues during freezing or prevent/delay ice formation. The lowest temperature that a liquid or gas can be cooled below its freezing point before becoming a solid, is called the supercooling point. We measured the supercooling point in isopods by placing them in a cooling bath hooked up to a computer that records changes in temperature. After freezing the isopods (insert evil laugh here), we put them in recovery containers to unfreeze. Next week, we’ll be able to see how many of the isopods survived and compare differences in cold tolerance between marine and terrestrial isopods.
Interestingly, the terrestrial isopods seemed to recover from chill coma much quicker than the marine. Why might this be? Could it have something to do with their different habitats? Perhaps, terrestrial isopods are exposed to more extreme temperatures in the winter, and so have adapted to survive in colder conditions. Maybe the results from our freezing experiment will give us give us a better idea of how these animals respond to the cold.