Pill Bug Leaf Preference Experiment by Zoe Du, Tien Van, Cammie Edwards, Solace Asong, and Natalie Durland
Biol & 212, Sec AA
Winter 2018
Blog Assignment #5 | Research Project
27 February 2018
Pill Bug Leaf Preference Experiment
By: Zoe Du, Tien Van, Cammie Edwards, Solace Asong, and Natalie Durland
Our experiment tested pill bug leaf preference. We wanted to see how pill bugs would react and behave giving different conditions of leaves. The leaves we used in this experiment were strawberry leaves, which were collected from campus farm. We ran six trials (trials 1-3 without soil and trials 4-6 with soil) where we placed 8 pill bugs in a choice chamber and recorded how many pill bugs were in each chamber at one minute intervals for 10 minutes. Each chamber had approximately the same volume of leaves but with different percentages of fresh leaves (0%, 25%, 75%, or 100%). For our observation, we wanted to see if the pill bugs preferred a particular chamber with a corresponding leaves condition. We predicted and hypothesized that the pill bugs would prefer the chamber with 75% or 100% fresh leaves because living leaves contain more nutrients and moisture and provide more surface area for the pill bugs to hide under.
Figure 1: An image of chambers setup for trials 3-6, containing soil and fresh leaves with different conditions. Amount of fresh leaves are 100%, 75%, 25%, and 0% respect to 1, 2, 3, 4.
Figure 2: An image of chambers set up for trials 1-3, containing leaves with different conditions without soil. Amount of fresh leaves are 100%, 75%, 25%, and 0% respect to 1, 2, 3, 4.
Since the pill bugs choose from four options (chambers), our degrees of difference was 3, which equates to a chi squared value of 7.8 if the results are significant. Our highest chi squared value among all six trials was 1.62, so clearly, none of our results were significant. We often observed pill bugs generally favoring a specific chamber during a trial, but the selected “favorites” were not significant across different trials and the expressed preference was still insignificant according to a chi squared analysis.
Our hypothesis was not supported by our observation and data. During our experiment, it was observed that the pillbugs preferred the chamber with dead leaves, possibly because dead leaves better resembled the natural control and environment of pill bugs. Dead leaves also had the color that was similar to the pill bugs and soil, thus, could help the pill bugs hide better. Moreover, the pill bugs appeared to preferred the chamber with 0% of green leaves in trials 1, 2, and 5; chambers with 25% and 75% of green leaves in trial 3; chamber with 75% of green leaves in trial 4; and never favored chamber with 100% green leaves. In the chamber with 75% of green leaves, the pill bugs often explored or chewed on leaves. Conversely, pill bugs in the chamber of 0% green leaves or chamber of 25% green leaves often chose to sleep or hide under the leaves. These observations suggested that the pill bugs, which range from light to dark brown in color, prefer dead leaves because they can use them to hide from predators. However, our data demonstrates that pill bugs do not have a significant preference for any ratio of dead leaves to fresh.
Figure 3: An image of a pill bug hides under a dead leaf in a chamber with 0% of green leaves. Notice that color of the pillbug is similar to color of the dead leaf.
Figure 4: An image of a pill bug feeds on a green fresh leaf. It climbs on top of the leaf and chew on it.
The most significant issue with this experiment was dealing with pill bugs that refused to choose a chamber and instead stayed in the center of the chamber because they were dead or inactive. In trial 3, two pill bugs were replaced during the experiment because one was dead and the other was completely inactive. In trial 5, two pill bugs never left the choice chamber, and in every trial, at least one pill bug would become stuck on its back or distracted with a clump of soil, a rock, or a twig.
Trials 4 through 6 had the same ratios of leaves with a small, even layer of soil. In these experiments, we expected the pill bugs to show a more significant preference for either green leaves’ nutrients or dead leaves’ cover and instead found that pill bugs were more active. In contrast to trials 1-3, where the pill bugs tended to stay in whatever chamber they initially chose, the pill bugs were active during Trials 4-6 and would wander the perimeter of the chambers they chose and wander between chambers. The pill bugs also gravitated towards tall leaves during trials 4-6 and tried to escape the chamber by climbing on them, which may have impacted our results. In addition, it became harder to keep track of the pill bugs since some would burrow under the leaves and in the dirt.
If another group were to repeat our experiment, we would recommend keeping the pill bugs active by keeping the center chamber clean and free of distracting soil. It’s also helpful to keep soil levels relatively low and use the glass cover to keep the pill bugs inside the chambers. Furthermore, another group could get more precise data by running more trials using more pill bugs and running each trial for longer than 10 minutes (even overnight). In addition, while running the experiment, we recommend to observe the pill bugs more carefully and pay more attention to their behavior.
For other groups who used pill bugs and chambers: did you see similar problems with the bugs staying in the center chamber sprawled out on their back or rolled in balls? If so, did you come up with any methods to limit or stop them from doing this? Furthermore, how did you keep the pill bugs to stay active and cooperative?
Hey guys! We also had an experiment with pillbugs. We had the same issue with our bugs dying as well. I feel as though the bugs are very sensitive to change. This made could make the bugs die easier. The bugs we had were also inactive. We even went out to the woods to gather more bugs for our test, and they didnt move a lot. I think next time we could both use more active insects, for better data results.
ReplyDeletehey guys
ReplyDeleteOur group did use pill bugs but not chambers. After reading your post, I would think that the pill bugs would choose fresh leaves than dead leaves. Its interesting its the other way around but your explanation makes sense that they would want to camouflage with the leaves and hide from predators.
I know, It was surprising of how our pill bugs were reacting in the experiment. They actually did feed on fresh leaves in the experiment but after some time, they move to the dead leaves in the soil to hide from predators. Some of our pill bugs were even trying to leave the chambers. It was really crazy to see how they were acting in the chambers.
DeleteMy group also used pillbugs for our research and did come across the same problem with the pillbugs stuck on their backs or staying in the middle. We just tried to move them to be able to stand on their feet and start walking. Most of the pillbugs that we flipped over did start to move to one of the chambers. But there were some that did not pick a preference to any of the chambers. We did not try to force any of the pillbugs to move since their inactive behavior shows something about the environment that they were in. It is interesting to see what the experiment could turn into with the suggestions you mentioned regarding the increase in activity.
ReplyDeleteHey guys! I agree that I think that pill bugs would generally tend to eat the "brown" leaves since they are detritivores and eat decaying matter. As far as pill bugs getting stuck on their backs, a way that my group solved this problem was to either increase the amount of pill bugs or introduce some crumpled up piece of paper (or some other highly texture matter) into the chambers for the pill bugs to grab onto and pull themselves back upright. Of course, paper may not be best for this experiment, but perhaps crumpling leaves or having washed rocks with rough textures would work. Also, insects aren't very active when they're cold and sometimes you can just be unlucky and get some sickly or old ones that tend to die. Getting some smaller pill bugs and storing them in relatively warm place might help their activity levels, and so prevent some error due to those reasons stated earlier.
ReplyDeleteHey guys, its too bad that you couldn't use your initial test organism. My group also used pillbugs, but didn't use the choice chamber. We came across the same problem of keeping them active because they would sometimes just stay at the edge of the container. I agree that when using pillbugs, it is better to let the experiment run for a long period of time. The problem with leaving them over night is that we cant observe their behavior throughout the night.
ReplyDeleteHey Everyone! This experiment sounds very interesting! I didn't think of something like this at all! My group chose to use pill bugs as well but we opted for individual containers versus the choice chamber. Can't wait to see what the experimental results are!
ReplyDelete