The Effect of an Acid and a Base on the Behavior of Pill Bugs
Abstract:
This lab was completed to test whether or not an acid or a base would have a profound
effect on the behavior of the isopod. Given 10 pill bugs to place inside a test chamber surrounded
by filter paper soaked with water, our control, an acid and a base. We then observed the isopods
for 10 minutes cataloguing their actions and behavior. Using this data and graphing it a
correlation was found between isopods and their affinity for the filter paper soaked in ph neutral
water in both part a and part b of this experiment. Even when given the choice of which liquid
substance to aggregate to they still landed over at the water choice chamber. This effectively
disproves the hypothesis and initial predictions.
Introduction:
Terrestrial isopods are land dwelling crustaceans, commonly known as sow bugs or pill
bugs (or roly-poly). They are related to lobsters, crabs, and shrimp, which means terrestrial
isopods breathe with gills and have many other body parts that are similar to marine crustaceans
(see the two diagrams above). While they look similar, sow bugs are different from pill bugs. Pill
bugs will curl into a ball when threatened whereas sow bugs will attempt to flee. This behavioral
instinct is unique to the pill bug. In this case we studied the effect of the pill bugs behaviors
when exposed to acidic and basic environments. We predicted that if the pill bugs were placed in
an environment with 3 chambers for water (control), an acid (lemon juice), and a base (Clorox)
then the bugs would aggregate towards the base because it may be more suited to their natural
environment. If this hypothesis is supported by the data, then predominantly the pill bugs will
remain in the basic chamber for the duration of the 10 minute period of observation time. We
estimated at least 4-5 pill bugs to remain inside the basic chamber for the duration of the
experiment.
Objectives:

Conduct experiments examining the responses of isopods to various environmental
factors
•
Design and conduct an investigation of animal behavior
•
Develop basic experimental design skills
Variables:
Independent variable: The moist filter paper.
Dependent variable: The pill bugs.
Control: Dry filter paper.
Constants: (1) Area/test environment will be kept clear of debris. (2) All pill bugs will not be
given a food source for the duration of the experiment.
Hypothesis & Justification:
If pill bugs are placed in an environment with dry and wet filter paper then the rill bugs
will choose to go to the wet paper because it is most like its natural habitat.
Materials:

Isopods

Filter paper

Choice chambers

Petri dishes

Lemon juice (acid)

Clorox (base)
Procedure:
1.
Place 10 pill bugs and a SMALL amount of bedding material in a petri dish. Pill
bugs generally do not climb, but if they do, you may cover the dish with plastic wrap or
the petri dish cover.
2. Observe the pill bugs for 5 minutes. Make notes on their general appearance, movements
about the dish, and interactions with each other. Notice if they seem to prefer one area
over another, if they keep moving, settle down, or move sporadically. Note any behaviors
that involve 2 or more pill bugs. These may include agonistic behavior. Agonistic
behavior is exhibited when animals respond to each other by aggressive or submissive
responses. Often the agonistic behavior is simply a display that makes the organism look
big or threatening. It is sometimes studied in the laboratory with Bettas (Siamese fighting
fish). Another behavior you may see is mating behaviors. These may involve a complex
series of activities that facilitate finding, courting, and mating with a member of the same
species.
3. Make a detailed sketch of a pill bug that fills this space. Make sure your drawing has the
correct number of legs, proportions.
4. Carefully put 5 isopods on either side so there is a total of 10 isopods in your choice
chamber. Cover each side with an upside down Petri dish. Be careful, the isopods are
likely to try to escape during your experiment if you leave any gaps.
5. Count how many isopods are on each side of the choice chamber every 30 seconds for 10
minutes, and then record your data in Table 1. Continue to record even if they all move
to one side or stop moving. If anything unusual happens (some isopods stop moving for a
long time, some escape, etc.), be sure to record it in the table.
6. Return your isopods to the Petri dish you used to gather them initially.
7. Graph both the number of isopods in the wet chamber and the number in the dry
chamber using graph paper over the 10 minutes.
8. Repeat steps 1-7 for comparative experiment.
Qualitative Data:
The pill bugs exhibited a lot of kinesis. They moved around increasingly less inside the
area between the test chambers with time. After around the first minute and a half all 10 pill bugs
settled into one of the three test chambers. After a while the majority of the bugs all migrated
into one chamber, formed in on each other and then defecated. Sometimes the isopods would
walk over each other instead of turning or sidestepping each other. The isopods also kept
attempting to flee the choice chambers. One actually got out and ran in a straight line.
Quantitative Data:
0
1
0
0
0
1
2
2
3
2
2
4
5
1
3
2
4
3
3
1
4
4
2
4
2
2
4
3
2
3
2
6
2
3
5
1
9
2
4
4
1
9
3
2
5
1
9
3
2
5
1
9
3
2
4
1
9
2
1
5
0
10
2
1
7
2
8
3
1
6
0
10
3
1
6
0
10
3
0
6
1
8
2
0
7
1
9
3
1
5
1
9
3
1
7
1
9
2
2
6
1
9
2
3
5
1.25
7.6
2.65
1.85
4.7
Calculations & Statistical Analysis:
Chart A:
The Effect of Water on the Behavior of Isopods
12
10
8
6
4
2
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Dry
5
5.5
6
6.5
7
7.5
8
8.5
9
9.5 10
Wet
The isopods seemed to favor the damp filter paper chamber over the dry chamber.
Chi for part A:
Null:
Chart B:
The Effect of a Acid and Base on The Behavior of Isopods
8
7
6
5
4
3
2
1
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Acid
5
Base
5.5
6
6.5
7
7.5
8
8.5
9
9.5 10
water
Near the end of the experiment the data shows the isopods settled mostly in the water chamber
(control).
Chi for part B:
Null:
Conclusion:
By completing this experiment I’ve now understanding of the principles of taxis and
kinesis in nature. By studying these isopods I have seen an animal’s response to its environment
based on instinct. This lab has also taught me a basic understanding of experimental design and
its process. I’ve learned that along with observation numerical and statistical data must be found,
recorded, and calculated in order to come up with a coherent and reliable result. While my
hypothesis may not be entirely accurate this is the nature of experimentation, as I did not know
before that a base has no bearing or effect on an isopods behavior. In fact it can be inferred that
the isopods discerned the PH differences in the 3 liquids and actually prefer water. But this
requires further experimentation. Also upon further research it looks like isopods breathe with
gills which is why they require areas of high humidity to survive (i.e. under a rock, dense leafy
areas). Isopods also prefer pH levels of soil ranging from neutral to slightly more acidic
environments.
Analysis:
1.) No. not every group will receive the same results for the moist dry experiment for
although this is a controlled experiment it is probable that the pill bugs were scared
by our presence or were just acting randomly and out of duress from being removed
from their preferred conditions.
2.) Improving the quantity for this particular set of experimental data would greatly
increase the dependency of the final conclusion.
3.) Their experiment would be far worse. 2 isopods and 4 minutes are inadequate
numbers to effectively come up with a dependable result. Although some similarities
may occur in the data, 10 isopods with 10 minutes is still far more reliable.
4.) In order to accurately test these isopods behavior in the environment the choice to
move between the two choices: dry and wet, had to be there or else the data would be
unusable.
5.) Isopods show taxis toward moist/dry conditions. After observing their movements it
would seem a majority of the isopods sought out the water filter paper and remained
in its choice chamber.
6.) These isopods instinctively going to seek out and remain near a humid/wet
environment, so it is likely one of our groups encountered a similar occurrence in
data. However there is always chance occurrences in data that cannot be accounted
for especially due to our limited lab resources.
7.) I’d expect isopods to be found in a very moist/ damp, dark environment. Based on the
data it seems they value water over all else which makes perfect sense seeing as how
their gills need to be wet for them to breathe through. You could expect to find rolly
pollies under rocks, damp forest floors, and under flower pots.
References:
Isopod, Pillbug, Sow Bug Information. (2004, March 25). Isopod, Pillbug, Sow Bug Information.
Retrieved September 19, 2014, from http://insected.arizona.edu/isoinfo.htm
Potter, M. (2013, January 22). SOWBUGS AND PILLBUGS. Sowbugs and Pillbugs. Retrieved
September 19, 2014, from http://www2.ca.uky.edu/entomology/entfacts/ef439.asp