Rollin’ with the Pollies

This week in BIOL 326 we trekked to Pacific Spirit Park to capture terrestrial isopods. Also known as wood lice, pill bugs, sow bugs, or rollie pollies, these fantastic critters are every child’s favourite creepy-crawly (well, they certainly are mine)! It is important to note, though, that not all isopods roll up into balls! Of the ones we collected on our little adventure, only the Armadillidium vulgare deserved to be called rollie pollies.

Anyways, without further ado, roll the Intro!

~ Whoops! Wrong song. ~

Well…moving along now…

In Pacific Spirit Park, we gathered isopods from logs next to trails. Our goal was to compare the number of isopods on the tops of logs and on the bottom. Not surprisingly, for most logs, more isopods were found on the bottom, and considering this observation, we asked ourselves why? We collected some of these isopods and took them back to the lab to perform some choice tests to answer this question.

Captive isopods in their cozy waiting room.

Captive isopods in their cozy waiting room.

To do that, we proposed three hypotheses, and tested each one using simple experiments and extremely scientific equipment (on a budget of course). The three environmental factors that were tested were moisture, temperature, and light. We used electrical tape on small Petri dishes to simulate light and dark environments, and moistened filter paper halves in Petri dishes to simulate moist and dry environments. To simulate warm and cool temperatures, hot and ice water bags were placed under painstakingly crafted aluminum boats (our craftsmanship was so advanced that even the government wouldn’t be able to read our minds if we wore them as hats). Individual pill bugs were placed in the test environments, and after 2 minutes, their choice was observed based on where they were.

Our critter friends vastly preferred moist environments over dry ones. Considering their biology, this is expected, since isopods actually breath with gills! To keep their gills from drying up, they need to keep them moist, and the underside of logs would be an ideal environment for this. On a related note, our isopods also preferred cooler temperatures. Surprisingly, there wasn’t a significant difference in the preference of dark or light environments. Given that we found way more isopods on the dark underside of a log than on the bright, exposed upper surface of a log, we expected isopods to prefer dark habitats. However, our tests were performed on a sample (a tiny portion) of the forest isopod population, so our results might not accurately represent all isopods everywhere. Perhaps the undersides of logs provide another advantage for isopods, such as protection from predators, or providing food. Since isopods eat decaying matter, rotting plants, fungi, and animals under the log would make a tasty and abundant meal for them. The next time we investigate rollie pollies, we can try testing these questions out.

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