Name: ______________________________________ Date: ________________________ Period: _____
CRAYFISH DISSECTION
Introduction: During the next two days, we will be working on the
anatomy, both internal and external, of the crayfish. YOU MUST
WEAR SAFETY GOGGLES AT ALL TIMES. THERE WILL BE NO
FOOLING AROUND WITH THE EQUIPMENT FOR THE LAB. Any problems should be reported to
the teacher.
External Anatomy:
Each pair will be given a crayfish to observe the external features that will help with labeling
and answering questions.
1. When you have your crayfish in the tray, locate the 1st, 2nd, and 3rd MAXILLIPEDS. These
are used to manipulate food. The largest one is the 3rd, the 2nd is underneath that, and
the 1st is underneath the 2nd.
2. The MANDIBLE is used to crush and grind food up (it is the jaw). Locate the mandible.
3. Locate the ANTENNAE. How many pairs should a crayfish have? _______________
4. Locate the EYES which are on eyestalks called pedicles. What are the eyes of arthropods
able to do? ______________________________________________________________
5. Look at the body of the crayfish. Locate the CEPHALOTHORAX and the ABDOMEN.
Name another animal that is segmented with only a cephalothorax and an abdomen.
________________________________________________________________________
6. The hard exterior of the cephalothorax is called a CARAPACE. Locate this. What do you
think that this does? _______________________________________________________
7. Locate the CHELIPEDS (claws). Move the claw around to see how it bends and in which
direction. This is the first walking leg of the animal.
8. Behind the chelipeds are WALKING LEGS. How many pairs are there? _______________
9. Remember that arthropoda means jointed foot. Move the walking legs around to see
how the joints work.
10. Notice that the abdomen is also segmented. On each of those segments are
appendages called SWIMMERETS. How many pairs of swimmerets are there?
_________
11. The last segment of the abdomen (the tail) is specially designed. What do you think it
helps the crayfish to do? ___________________________________________________
12. Locate the TELSON (the last segment). On the outside of the tail of UROPODS that help
the crayfish swim backwards. Locate them.
13. Time to figure out the gender!! To figure out whether you have a male or female you
need to look at the swimmerets. Locate those again.
If the first pair of swimmerets are larger and stiffer than the others, you have a
MALE!
If the first pair of swimmerets are about the same size as all of the others, you
have a FEMALE!
Indicate which gender you have: ___________________________________________________
Based on your external dissection, label the following diagram with the correct terms.
1.) Crayfish belong to the kingdom ____________________________, phylum
______________________, and subphylum ______________________________.
2.) What are the characteristics that all arthropods have? ___________________________
________________________________________________________________________
________________________________________________________________________
3.) Which appendage determines the sex of the crayfish? ___________________________
4.) What covers the cephalothorax? _____________________________________________
5.) What does the mandible do? ________________________________________________