Introduction:
Crayfish live in streams, ponds, and swamps, usually protected under rocks and vegetation. They may walk slowly over the substrate of their habitat, but they can also swim rapidly using their tail. These organisms are segmented.
Procedure:
1. On the picture below, label the following structures: Walking legs, compound
eyes, cephalothorax, abdomen, and antennae,
Give the function of the following external parts:
a). Antenna ______________________________________________________________
b). Swimmerets ___________________________________________________________
c). Walking Legs __________________________________________________________
d). Tail __________________________________________________________________
2. Examine the length of the swimmeret closest to the carapace. If it is longer than the others the animal is a male. What is the sex of your specimen? ______________________.
3. Locate the carapace at the end of the cephalothorax. Place the point of your scissors under the posterior edge and cut straight down the center to the head. Make two lateral cuts, one near the head and the other near the end of the carapace. Remove this section of the exoskeleton. You have exposed the gills. Describe the gills _____________________
____________________________________________________________________
What is the function of the gills? ___________________________________________
4. Grab one of the walking legs and move it back and forth while looking at the gills. Explain what is happening (Be specific). _______________________________________________________________________
Use Figure 2. Internal Anatomy of the Crayfish to help you locate the following organs.
5. Locate the stomach in the head region. It is a large sac-like structure. what is the function of the stomach? _______________________________________________________. What internal organ is connected just behind the stomach? _________________________. What is its function?___________________________.
6. What part of the crayfish's body contains most of its internal organs? _______________.
7. What is the crayfish's exoskeleton made of ? _________________________.
8. Locate the green gland. Describe where it is found. _____________________________.
9. What is its function? __________________________________________________.
Figure 2. Internal Anatomy of the Crayfish.
Summary:
1. What phylum does the crayfish belong? _________________________.
2. What is the main characteristic that places it in this phylum? ______________________.
3. What does the term molting mean? _________________________________________.
4. What are the respiratory organs of the crayfish? _______________________.
5. What type of circulatory system does the crayfish contain? _______________________.
6. What is the function of the large claw-like walking feet of your speciman?_______________________________________________________________
7. What part of this animal is used for food by humans? ___________________________.
8. Why are crayfish classified as coelomates? __________________________________
________________________________________.
9. Why are they classified as protostomes? ______________________________________
______________________________________________________.
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