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Activity: Gastropod Shell Description

NGSS Crosscutting Concepts:

NGSS Disciplinary Core Ideas:

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)

Table 3.6. Features of gastropod shells. Letters refer to Fig. 3.56.1.

  1. Body whorl. The part of the shell the animal lives in
  2. Spin. Part of the shell from its tip (apex) to the body whorl
  3. Shoulder. The top of the body whorl
  4. Canal. A tubular extension of the body whorl
  5. Suture. Spiral grooves where one whorl overlaps another
  6. Whorl. Each "wrap" of the shell as it grows
  7. Shell ornamentation. The knobs, spines, and colors on the outside of the shell
  8. Aperture. The opening into the shell interior
  9. Lip. The outer and newest edge of the aperture
  10. Columella lip. The rounded inner lip of the aperture
  11. Notch. An indentation at the bottom of the shell beside the tip of the canal
  12. Varices. Raised ribs, usually running vertically, caused by periodic thickening of the outer lip during shell growth (not shown in drawing)
  13. Operculum. A plate that seals the aperture in many shells (not shown in drawing)
  14. Apex. Pointed tip of the body whorl

<p><strong>Fig. 3.56.2.</strong> Gastropod shell shapes with the aperture colored black</p><br />


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).
      <p><span style="font-size: 13.008px;"><strong>Fig. 3.56.5.</strong> Gastropod shell with apex up and aperture facing the observer. Note the apertures that open to (<strong>A</strong>) the left and <strong>(B</strong>) the right.</span></p>
    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.

 

Activity Questions: 
  1. Gastropod shells are exoskeletons.
    1. What is the function of the shell in these organisms?
    2. What are some of the advantages and disadvantages of having an exoskeleton?
       
  2. What general statements, if any, can be made about
    1. the location of the aperture of gastropod shells?
    2. the direction in which the shells coil?
    3. the colors of the shells?
    4. the patterns of the shells?
       
  3. How do gastropods grow larger? How does their growth differ from the growth of bivalves?
     
  4. What features of gastropod shells
    1. vary among individuals of the same species?
    2. do not vary among individuals of the same species?
       
  5. Suggest how shell shapes may reveal adaptations to their environment. Give reasons for each suggestion. What shell shapes might be an advantage for gastropods that
    1. live clamped to wave-pounded rocks?
    2. move through sand or mud?
Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.