Materials Included In Kit

Additional Materials Required

Prelab Preparation

Isopod Culture

1. Use a large glass or plastic container with a lid as the culture container. Cut small holes in the lid for air. Flinn No. FB0268 works well.
2. Add 1 to 2 inches of pesticide-free soil to the bottom of the culture container.
3. Add enough water to moisten the soil.
4. Place organic matter, such as leaf litter, dried grass, sawdust or pesticide-free bark, on the surface of the soil.
5. Gently place the isopods into the culture.
6. Add a slice of raw potato every few days for food. Remove the potato before mold begins to grow.
7. Keep the culture at room temperature, occasionally checking the moisture level and the amount of organic material.
8. Keep the culture out of direct sunlight.
9. Juvenile isopods look like small adults.

Safety Precautions

Please consult current Safety Data Sheets for additional safety information for chemicals used in student-designed experiments. Remind student to wash hands thoroughly with soap and water before leaving the laboratory.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for proper disposal of Type IV Biological Materials, and review all federal, state and local regulations that may apply, before proceeding. Never release the isopods into the local ecosystem. They may unknowingly harbor pathogens that could decimate the local population.

Lab Hints

• Enough materials are provided in this kit for 30 students working in pairs. Both parts of this laboratory activity can reasonably be completed in four 50-minute class periods. The students should read the Background, Safety Precautions and Procedure sections before coming to lab. A second class period is necessary to develop an inquiry procedure. During third class period students conduct their experiments. Finally, the data compilation and reports can be completed either in class or outside of class and the reports may be presented in class or as posters.
• Potential inquiry items:

Weak acid vs. neutral—pH of 5 to 6.5. More acidic solutions may harm the isopods.

Weak base vs. neutral—pH of 7.5 to 9. More alkaline solutions may harm the isopods.

Warm vs. room temperature—hand warmer, Flinn Catalog No. AP1931.

Cold vs. room temperature—cold pack, Flinn Catalog No. AP6267.

Wavelength of light—colored cellophane, Flinn Catalog Nos. FB0596–FB0598.

Surface texture—sandpaper, Flinn Catalog No. S0165.

Choice of food—potato, carrot, lettuce, walnut, maple, oak, evergreen leaves.

Substrate choice—wood chips, cedar chips, white paper towel, brown paper towel, soil, vermiculite.

• Ants, termites, ladybugs or other local insects may be used instead of isopods.
• Isopods can be purchased from Flinn Scientific, Inc. (Flinn Catalpg No. LM1218) or trapped in most wooded or garden areas. Cut a deep hole into a potato. Place the potato into the woods or garden area and cover with leaves. After a few days, check the potato. Gently transfer any isopods into a culture container. Never release animals back into the environment. Released animals often become prey or may inadvertently transmit a pathogen to the local population.
• Some isopods may move toward the brighter area instead of toward the shaded area. A virus causes a behavioral change, which causes these animals to move to an area where they will likely be eaten by a bird or other predator. The isopod is a vector host for the virus.

References

Tree of Life Web Project. http://tolweb.org/Isopoda (accessed May 2018).

Wright, J. Department of Biology, Northern State University, Aberdeen, SD. 1997. http://www3.northern.edu/natsource/INVERT1/Pillbu1.htm (accessed May 2018).

Introduction

Isopods are often used in behavior studies. They are clean, odorless and do not transmit human pathogens. They do not bite, sting or pinch. Long term colonies are easy to set up and maintain in a plastic container containing soil, wood or cardboard, slices of potato and an occasional spray from a misting bottle. In their native environment they play an important role by foraging on dead plant material turning the dead leaves into natural fertilizer for new plants. Design a behavior experiment using these sturdy bugs.

Concepts

• Experimental design

• Taxis
• Behavior
• Kinesis

Background

The order Isopoda contains about 10,000 species. More than half of the species are aquatic, most of which are marine species. The remaining species live on land. Like other crustaceans, isopods have a brain, compound eyes, a hard exoskeleton, jointed appendages and antennae. The hard exoskeleton is made of overlapping plates instead of a single sheet of armor. The overlapping plates allow the body to bend. In fact, some species of isopod roll into a ball when touched. The species that roll when touched are known by the common names roly poly bugs or pillbugs. Other species move away from the touch and do not roll up even though they look very similar to those that roll. Terrestrial isopods that don’t roll are often called woodlice or sow bugs.

Land isopods breathe through structures that must remain moist. They do not burrow deep into the soil like earthworms. Instead, they seek shelter under small rocks, wood chips or leaf litter. They are prey to both vertebrates and invertebrates and are typically seen at night (nocturnal).

In this laboratory the behavior of the isopod will be observed. Deliberate movement away from or toward a stimulus is called taxis. Random movement due to a stimulus is called kinesis. Since taxis can be either away from or toward a stimulus it is important to note which way the organisms move. Movement toward the stimulus is called positive taxis. Movement away from the stimulus is called negative taxis. But what is a stimulus? A stimulus can be anything that has the potential to cause a response. For example, light is a stimulus. Brine shrimp, another type of crustacean, moves toward a small light if kept in a dark tank. This is an example of positive phototaxis. Notice that the type of stimulus is a prefix. Other prefixes are aero-, chemo-, thermo-, gravi-, magneto-, electro-, phono- and thig- (touch).

Experiment Overview

In the first part of the laboratory students will use a hand lens or stereoscope to closely observe the body structures on the isopods. Observations about the movement of the isopods will also be noted. In the second part of the laboratory students will research and plan a behavioral study using the isopods. Next, students will conduct their approved experiments and present their group findings.

Materials

Safety Precautions

Wash hands thoroughly upon completion of laboratory work with living materials. Follow all other safe laboratory procedures.

Procedure

Part 1.

Remember that you are working with living organisms. Treat them with care and respect.

1. Place a damp piece of paper towel into a Petri dish.
2. Use a spoon to collect 3–5 isopods from the isopod colony.
3. Use a hand lens or stereoscope to observe the isopods. Recall that isopods live in dimly lit or dark areas and are nocturnal. Use as little light as possible when observing the animals. Do not touch them yet. Just observe how they move and behave. Record your observations.
4. Gently touch each isopod. Are they pillbugs, sow bugs or both types?
5. Sketch the animal and label the drawing.
6. Place a leaf, small piece of potato or other food source in the Petri dish and observe the animal eating.
7. Return the isopods to the isopod colony.

Part 2.

1. Consider the following questions while reflecting upon your knowledge of taxis and isopods.

1. Reread the Background section or research the different types of taxis and kinesis.
2. For example, would the isopods have positive or negative taxis or kinesis for a lit area versus a dark area?
3. If both types of isopods are available, do pillbugs respond to the stimulus in the same way as sow bugs?
4. Is one taxis stronger than another taxis?
5. Discuss several different potential experiments.

2. Plan, discuss, evaluate, execute and justify an experiment to test a question regarding taxis and isopods.

1. Decide upon one question your group would like to explore.
2. Develop a testable hypothesis.
3. Discuss and design a controlled experiment to test the hypothesis.
4. List all materials required and research the safety precautions that will be implemented to keep yourself, your classmates, your instructor and the animals safe during the experimental phase of the laboratory.
5. Determine how to collect and record data.
6. Determine how the data will be analyzed to test the hypothesis.
7. Review your hypothesis, safety precautions, procedure and proposed data analysis with your instructor to be approved prior to beginning the experiment.
8. Once the experiment and analysis are complete, evaluate your hypothesis and justify whether or not the hypothesis was supported by your data.
9. Present and defend your findings to the class.
10. Make suggestions for a revised or new experiment to modify or retest your hypothesis.

3. Consult your instructor for appropriate disposal procedures.