Objectives:

·  Observe various aspects of a terrestrial isopod (DAY 1)

·  Conduct experiments examining the responses of isopods to various environmental factors (DAY 2)

·  Design and conduct an investigation of animal behavior (DAY 3)

**Isopods are also called sowbugs and pillbugs. Be Gentle!

Background Information

Ethology is the study of animal behavior. This involves observing an organism’s behaviors, interpreting what is observed, and research different organisms. Ethologists study and observe an organism’s reaction to the environment around them.

An animal can display many different types of behaviors, two being taxis and kinesis. Taxis behaviors are deliberate movements toward or away from a stimulus. Kinesis is a random movement that is not oriented toward or away from a stimulus. Taxis behaviors are exemplary of the physiological needs of an organism. Other behaviors are agonistic (aggressive or submissive actions toward another organism) and mating behaviors.

In today's lab we will examine the movement behavior of "Pill Bugs"

Part A-Observations

Materials:

The following materials will be needed to complete the experiment: 5-10 pill bugs, 2 animal behavior petri dishes, 2 pieces of filter paper, 1 camel’s hair brush Blank paper, pencils. Metric rulers.

Procedure:

1.  First, place the 2 pill bugs and some "bedding" into a petri dish and take general observations of their movement and interactions for at least 10 minutes. Notice where they go, how they interact and anything else you may see. Do Not, prod or push them around. We want to observe their "natural" behavior.

Make a list of the data you have collected.

Example Qualitative Data: General Observations on Behavior

a.  The larger pill bugs climbed over the smaller sized ones.

b.  Movement mostly around edges of tray.

c.  Legs move in quick, fluid motion.

d.  Use antenna to sense closeness of other isopods.

e.  When flipped on back side, will kick off from ground or other pill bugs to flip back over.

f.  How do the pillbugs seem to sense their environment?

g.  Are they all the same species?

h.  Can you tell differences in males and females?

i.  Do they have eyes eyes do they have?

j.  Do they have legs?

k.  Do they exhibit any dominance behaviors?

l.  How do they respire?

m.  How do they grow?

n.  What are some stimuli they seem to respond to?

Example Quantitative Data: General Observations on Behavior

2.  Sketch a Pill bug and try to label the "head" and the "tail" of the bug. Place a pillbug in a petri dish under the dissecting scope and make a Pill Bug Sketch on plain (unlined) paper.

Determine the relative proportions:

a. width : length;

b. height : length;

c. distance between eyes : width of body;

d. length of antennae : length of body.

2. Count the number of body segments.

3. Count the number of legs.

4. Locate the eyes.

5. Label the body parts.

6. Note the size of the pillbug.

Observe several pill bugs to determine whether or not they have an orderly structure that is consistent across all observed bugs.


Part B- Further Observations Orientation of Isopods in Response to Moisture (DAY 2)

Use the Behavior Chamber provided In this experiment, you will see the pill bug’s preference for a wet or dry environment. Place two pieces of filter paper in the choice chambers you have (see below). Make one filter paper wet, but not saturated and leave the other dry. With a paint brush or a pencil eraser, carefully place 5 pill bugs into the center of your petri dish opening.

Every 30 seconds count and record the number of pill bugs in each chamber. Do this for 10 minutes, even if the bugs aren't moving.

Pill bugs are crustaceans, and they respire through gills. Because of this characteristic, which situation would you predict? ______

Procedure: Set up your behavior chamber so that you have one side moist and one side dry (using paper towels or filter paper discs). Transfer 5 isopods to each side of the chamber (total of 10). Count and record the number of animals on each side of the chamber every 30 seconds for ten minutes, using a table like the one below.

You will need to include this data in your lab report!

Time / # in Wet / # in Dry / Other Notes
0:00
0:30
1:00
1:30
2:00
2:30
3
3:30
4
4:30
5
5:30
6
6:30
7
7:30
8
8:30
9
9:30
10


Graph the number of pill bugs in the wet and dry chambers ON THE BACK OR THIS PAGE:

Follow the graphing instructions below:

Graphing Instructions: Remember to graph the independent variable on the horizontal (X) axis and the dependent variable on the vertical (Y) axis. Your graph should have 2 lines: one representing the pillbugs in the moist chamber and another representing the pillbugs in the dry chamber. You can draw the lines in different colors or distinguish them by using different symbols for the points on the graph or the lines themselves (ex. solid vs. dashed). This will be a "dot-to-dot" graph. Be sure to include a legend describing which line represents which chamber.

Interpreting Your Graph: If the lines diverge from each other (go away from each other) at some point, then your pillbugs are likely showing a preference for the chamber represented by the line that is mostly going up. If the lines converge on one another (criss-cross a lot or are on top of each other a lot), then the pillbugs are not showing a preference for either chamber. Remember, that in science, no result is wrong. It is what it is. If this experiment is done in reality and the pillbugs don't behave as expected, it may be due to the fact that they are stressed from being manipulated for example.

Graph Page

TIME (minutes)


Part C - Student Designed Experiment (DAY 3-4)

Select TWO of the following factors to investigate and design an experiment to test it. (Use the procedure above as a guideline.) You may also propose your own test, check with your instructor. Consider that in science, testing variables separately provides the most useful evidence. You will also need to include data on these experiment in your lab report, similar to the chart above. Create your own data table and Perform your lab.

Factor / Possible Materials
Temperature / Cold pack, warm pack, ice, warm water
Light / Lamps, flashlights, dark construction paper, aluminum foil
pH / HCL, NaOH, vinegar, baking soda
Substrate (surface) / Soil, sand, bark, cedar, gravel
Odor / Ammonia, perfume, lemon juice
Food / Potato, fish flakes
Organisms / Crickets, earthworms, plants


Review Questions:

1. Taxis can be defined as..?

A.  Random movements

B.  Deliberate movements toward or away from a stimulus

C.  Vehicles for hire

2. What is the Independent variable in the Moist/Dry experiment shown in the above animation?

A.  Moisture

B.  The number of bugs

C.  Bug activity

D.  Time

3. Which of the below are the Pill bugs most closely related to ?

A.  Ants

B.  Bees

C.  Shrimp

D.  MCC students

4. What Physiological reason(s) could an animal have for choosing a specific environment?

Pill bug natural history

Classification

·  "Pill bugs" or "Sow bugs" Armadillidium Valgare

·  Phylum, Arthropoda; Class, Malacostraca; Order, Isopoda

·  This group includes shrimp and crabs, they are not really "bugs".

Appearance (Morphology) Color varies from dark gray to white with or without pattern

·  Three body parts: head, thorax, abdomen

·  One prominent pair of antennae (one inconspicuous pair)

·  Simple eyes

·  Seven pairs of legs

·  Seven separate segments on thorax

·  Paired appendages at end of abdomen called uropods

On the underside, females have leaf-like growths at base of some legs. These brood pouches hold developing eggs and embryos. The first two appendages on the male abdomen are modified as elongated copulatory organs.

Natural History

·  Food
Isopods are omnivores or scavengers feeding on dead or decaying plants or animals. Some may eat live plants.

·  Habitat
Isopods breathe with gills, so they are restricted to areas with high humidity, under rocks or logs, in leaf litter or in crevices. Some species are nocturnal.

·  Predators
Vertebrates and invertebrates.

·  Interesting Behaviors
Some species roll up into a ball when disturbed. Eggs (up to 100) are held in broad pouch on female. Juveniles look like adults and are soon liberated from pouch. Molting is in two stages. First the back half molts, then two to three days later, the front half molts. Coloration of both halves may be different at this time. Many species are fast walkers, but can be easily observed when held in the palm of the hand.

Impact on the Ecosystem

·  Positive
In their immediate vicinity, isopods do minimal soil improvement. Isopods are also a food source for other animals.

·  Negative
In greenhouses and southern states, large populations can eat and damage plants.

Collecting Live Insects

·  Where to find
Look under logs, moist leaf litter, flower pots (a day after they have been watered), outdoor pet dishes, and under paving bricks or stones. Isopods live where it is moist and usually in a shaded area. To attract them, water soil or leaf litter in the shade and cover with plastic, piece of plywood or cardboard. Keep the area moist and check under the covering in a couple days. If you are unable to find isopods they can be purchased from: Carolina Biological Supply Company.

·  How to collect
Before looking for isopods, prepare a container and tools to gather the isopods. If you are going to set them up in a container with soil in a day, you do not need to separate them from the soil (see rearing information). To collect them, use a spoon or shovel and a container. Look under a rock or log and be prepared to collect the isopods quickly before they scurry away from the light. Gently scoop up soil with the isopods and place them in the container. Look on the underside of the log or stone for others. They can be gently picked or brushed off with a finger into the container. Pill bugs often curl up and can be picked up individually or scooped up with the spoon. If you are going to keep the isopods a couple days before placing them in the classroom, use a plastic margarine or cottage cheese container with small holes poked in the lid and a moistened piece of paper towel lightly crumple inside. Use an old pie tin to sort the isopods from the soil before placing them in the container. The paper towel must be kept moist or they will die. When you are looking under rocks and logs be careful to avoid scorpions, centipedes and other animals that live there. Return the rock or log to the way it was when you found it.

Pill Bug Races
Select a pillbug based on whatever criteria desired.

Place the pillbug in the center of a 60 cm circle drawn on butcher paper.

Record the time it takes to hike 30 cm to the perimeter of the circle. This is the pill bug’s "qualifying time"

All pillbugs are seeded by qualifying time into a double elimination tournament. Head to head competition - first bug to the edge wins.

World record time was 9.33 sec for 30 cm, approximately 3 cm/sec !!!

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