Chapter 13: Mollusks, Worms, Arthropods, Echinoderms

A crayfish has a segmented body and a fused
head and thorax. It has a snout and eyes on
movable eyestalks. Most crayfish have pincers.
Real-World Question
How does a crayfish use its appendages?
Goals
■ Observe a crayfish.
■ Determine the function of pincers.
Materials
crayfish in a small aquarium
uncooked ground beef
stirrer
Safety Precautions
Procedure
1. Copy the data table and use it to record all
of your observations during this lab.
Crayfish Observations
Body Number of
Region Appendages
Head
Thorax
Abdomen
Function
Do not write in this book.
2. Your teacher will provide you with a crayfish
in an aquarium. Leave the crayfish in the
aquarium while you do the lab. Draw your
crayfish.
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3. Gently touch the crayfish with the stirrer.
How does the body feel?
4. Observe how the crayfish moves in the water.
5. Observe the compound eyes. On which
body region are they located?
6. Drop a small piece of ground beef into the
aquarium. Observe the crayfish’s reaction.
Wash your hands.
7. Return the aquarium to its proper place.
Conclude and Apply
1. Infer how the location of the eyes is an
advantage for the crayfish.
2. Explain how the structure of the pincers
aids in getting food.
3. Infer how the exoskeleton provides
protection.
Compare your observations with those of
other students in your class. For more help,
refer to the Science Skill Handbook.
LAB 379
Tom Stack & Assoc.