Sneaky little guys hiding under the logs of Pacific Spirit Park

They’re small and harmless, yet I couldn’t seem to get myself to touch them with my bare hands. These terrestrial isopods can easily be found under logs that are lying around in the forests of Pacific Spirit Park surrounding the UBC Vancouver campus. There are three species that can potentially be found Armadillidium vulgare, Oniscus assellus or Porcellio scaber. However, the Oniscus, is likely to be most commonly found around UBC. It can be distinguished by its’ shiny body which has paired white patches on each main body segment.

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Pacific Spirit Park – UBC Vancouver campus

On our trip to the park we measured the width and height of the logs we were observing and counted the number of isopods we could find crawling around on top of the log. We then flipped the log over and tried to count the number of isopods in the log and also those that were crawling in the soil below the log. Once we had recorded the numbers, we were supposed to collect these little creepy-crawlers in order to do further experiments on them in the lab. My partner and I struggled with this as we were using little sticks and leaves to get them into a Ziploc bag. It was even more challenging as they would hide in little crevices of the log so we couldn’t get a hold of them. Apparently no one else seemed to be as afraid of them as we were because we saw them using their hands to pick them. No thank you. I’m just proud of myself for being able to look at them without screaming like a little girl. Nonetheless, we were able to get our job done and our results showed that there are significantly more isopods below the log than there are on top of the log.

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The bottom side of a log after it had been flipped over

Back in our lab, we tested three different behavioral responses on these isopods. First we tested whether they preferred dark vs. light habitats by placing them in a petri dish which was half open to the room lighting and half covered with black electrical tape. Next, we tested whether they preferred wet vs. dry habitats by placing the isopods in petri dishes which had one half with a wet filter paper, and the other with a dry filter paper. Lastly, we tested whether they preferred hot vs. cool habitats by placing an aluminum foil “boat” so that half of it was above ice and the other side was above hot water. We found that the isopods preferred dark, wet and cool habitats.

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Dark vs. light experimental set up

These lab experiment results make sense based on the patterns we found at the park. There were significantly more isopods below the log than there were above, and it is below the log where you found find a habitat which is dark, wet and cool. The top of the log can be directly exposed to sunlight leaving the isopods in the light and dried out and warm from the sun.

If you found this experiment super exciting, please feel free to refer to this paper for some interesting information: http://www.jstor.org/discover/10.2307/3564994?uid=3739400&uid=2129&uid=2&uid=70&uid=3737720&uid=4&sid=21104213348861

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