Exploring Our Fluid Earth

Materials

• Table 3.5
• Table 3.6
• Table 3.7
• Table 3.8
• Fig. 3.56.1
• Fig. 3.56.2
• Fig. 3.56.3
• Fig. 3.56.4
• Fig. 3.56.5
• At least four different gastropod shells
• Centimeter ruler
• Colored pencils (optional)

Image

Image caption

Fig. 3.56.1. Features of gastropod shells, using the shell of Zonitoides nitidus as example

Image copyright and source

Image adapted from Michal Maňas, Wikimedia Commons

Image

Image caption

Fig. 3.56.3. Gastropod shell measurements

Image copyright and source

Image by Byron Inouye

Image

Image caption

Fig. 3.56.4. Gastropod aperture margin descriptions

Image copyright and source

Image by Byron Inouye

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Image caption

Fig. 3.56.2. Gastropod shell shapes with the aperture colored black

Image copyright and source

Image by Byron Inouye

Procedure

1. In Table 3.5, make careful pencil draw¬ings of each gastropod shell with its apex up and its aperture facing you. Fill most of the space in the table, even if the shell is small.
    
2. Identify the features of each shell using Fig. 3.56.1 and Table 3.6, Some shells will not have all the structures shown. Others will have structures that vary from one shell to the next.
    
3. Using the Figs. 3.56.1 to 3.56.5 as guides, examine each gastropod shell for the features in Table 3.6. Record your observations in Table 3.7. Make checks in the boxes for features the animal has. Leave the other boxes blank.
   
   1. Place the shells on your notebook. Position the shells with the apex towards the top of your notebook, the notch towards the bottom of the notebook, and aperture facing you. Decide which shape in Fig. 3.56.2 best fits each shell. If the shell does not match any of the shapes in Fig. 3.56.2, sketch it and invent a descriptive name for the shape.
   2. Measure and record the length (in centimeters) of the entire shell, the aperture, the spiral, and the body whorl (Fig. 3.56.3).
   3. Look at the margins of the aperture. Check the phrase that best describes the presence or absence of teeth on the columella lip and outer lip (Fig. 3.56.4).
      
      

      Fig. 3.56.5. Gastropod shell with apex up and aperture facing the observer. Note the apertures that open to (A) the left and (B) the right.

      Image courtesy of P.H. Nyst, adapted from Wikimedia Commons

   4. Look for a lip canal, notch, varices, and operculum. Check those you find. Notice whether the aperture opens to the left or to the right. See Fig. 3.56.5.
   5. Examine the sculpturing for such features as ridges, knobs, spines, and
      grooves.
   6. Describe the colors and patterns. Sketch them or use words like spotted or striped.
   7. Record other visible features, includ¬ing erosion, scar marks, drilled or bored holes, and encrusting by other marine life.
   8. Record other observations.
       
4. Reposition the gastropod shells so that you are looking down on the apex. For the following steps, record your observations in Table 3.8
   
   1. Sketch the spiral shape, sutures, and shoulders in Table 3.8.
   2. Observe and describe the direction of the spire as clockwise or counter¬ clockwise.
   3. Estimate and record the greatest width of the shell in centimeters.
   4. Count and record the number of whorls.
   5. Sketch or describe differences among the whorls. Note colors, pat¬terns, and sculpture.
       
5. (Optional) If resources are available, identify your gastropod species. Record their
   
   1. habitat
   2. home range
   3. diet
   4. typical lifespan
       
6. (Optional) Using the terms from steps 1–4 make a dichotomous key of five gastropods.
    
7. (Optional) Examine the coloration of several individuals of the same species. Observe and record how they vary in color, pattern, teeth, and sculpturing.