What to do When You are Way too Cold? Just Keep Eating!

 

Porcellio scaber isopods in their natural environment on a fallen log (Photograph by Llandinam)

Porcellio scaber, or pillbugs, are little critters everyone can find under logs and branches on the forest floor, but did you know these little creatures have very unique abilities allowing them to survive cold environments? This was what my independent project this term focused on.

P. scaber are ectothermic or cold-blooded animals, meaning they cannot produce enough body heat to control their own temperature. Instead, they rely on external temperature to warm up their body and all the chemical reactions that happens inside. A major problem ectotherms face is when the outside temperature is too cold and they cannot warm up. When this happens, everything in the animal from chemical reactions to blood movement slows down causing the animal to become very slow and sluggish. If the temperature drops even more, the animal goes into a state called cold coma, where although still alive, they remain unable to move until the temperature warms up. If they remain in the cold for too long, the animal will often die.

However, most ectotherms have ways to deal with the cold. Some animals simply migrate to warmer areas or burrow underground. Other animals change their internal processes to prevent freezing. You can learn more about the fascinating ways some ectothermic animals survive the cold through this video!

For my project, I decided to look at what will happen if I placed P. scaber in cold temperatures for a long period of time. To do this, I placed 10 P. scaber into my fridge which had a constant low temperature of 4°C. Half of these isopods got food while the other half did not. I also placed 5 other isopods in a 16°C room as comparison to the cold groups. After 5 days, I tested each isopod’s speed. As we already know, being ectothermic, isopods will become slower in cold temperatures, and that is exactly what I saw. The isopods of the colder group had a much lower speed. However, that was only true if they didn’t have access to food. The isopods in the fridge that had food did not show a slower speed, but instead, they were just as fast as the isopods in the warmer temperature.

Experimental setup of 10 P. scaber individually placed in my fridge with half of the isopods receiving food

This came as a big surprise as I didn’t expect simply giving isopods food can reverse the effects of cold temperature. With some research, there seems to be an explanation. Many animals can build antifreeze molecules in their body. These molecules are microscopic and protect an animal from the cold by getting rid of ice within the animal or protecting the animal’s cellular structures from cold damage. Researchers argue that when animals are fed, they have greater resources available to build these molecules and thus can survive better in the cold compared to starving animals. This may explain why my isopods showed higher speed in cold temperatures when food was given to them. You can learn more about how other animals use antifreeze and how human can potentially benefit from this research with this article.