Crayfish Dissection  

by Liz LaRosa

www.middleschoolscience.com

 Objectives:

• to observe the external and internal anatomy of a crayfish.
• to determine the sex of a crayfish using external anatomy.
• to collect statistical data on crayfish length and cheliped length.

1. Measure the length of your crayfish in cm from the rostrum to the telson and record in Table 1.
2. Draw the external dorsal view of your crayfish into Figure 1. 
3. Label the following: dorsal,anterior, posterior,head, antennae, thorax, abdomen, right cheliped.
4. Look at the ventral side of the crayfish.  Using your handout, see if you can determine the sex of your crayfish. Record in Table 1.
5. On the ventral side, locate and sketch (Figure 2) the following: dorsal,anterior, posterior, (cephalo)thorax, abdomen, right cheliped, walking legs, swimmerets, uropods
6. Carefully remove the carapace to expose the gills and interior cavity.
7. Make a sketch of the internal dorsal view in Figure 3. .  Label the following: dorsal,anterior, posterior, (Cephalo)thorax, abdomen, right cheliped,
8. Count the number of walking legs and record in Table 1.
9. Make an incision along the dorsal side of the abdomen.  Be careful not to cut too deeply.
10. See if you can find the intestine and muscles. Label in Figure 3.

Data: (leave a 1/2 page for each figure and table)

Figure 1: External Dorsal Anatomy of the Crayfish- be sure to label all parts!

Figure 2: External Ventral Anatomy of the crayfish- be sure to label all parts!

Figure 3: Internal Dorsal Anatomy of the crayfish- be sure to label all parts!

Table 1: Crayfish Information Table
 

Length of Crayfish in cm
Sex of crayfish
# of Abdomen Segments
Length of Right Cheliped in cm
Number of Walking Legs

 

Figure 4: Stem and Leaf of Crayfish Length in cm

Figure 5: Stem and Leaf for Cheliped Length in cm

Table 2: Summary Data Table of Crayfish Length and Cheliped length (cm)

	Crayfish Length in cm	Cheliped Length in cm
n
max
min
range
sum
mean
median
Q3
Q1
IQR

Figure 6: Box Plot of Crayfish Length vs. Cheliped Length (cm)

 

1. What sex was your crayfish? How did you know?
2. Was there a pattern to how many tail segments the crayfish have?
3. What length in cm was the longest/shortest crayfish? What about the median?
4. Mathematically determine if there is a relationship between cheliped length and crayfish length.

For pictures of the dissected crayfish visit this wonderful site: http://biog-101-104.bio.cornell.edu/BioG101_104/tutorials/animals/crayfish.html