Investigation 2 - Identifying an Earthworm

Before participating in the National Worm Survey, you should practice identifying earthworms. This activity will give you an opportunity to become familiar with the Key to Reproductively Mature Earthworms Found in Canada before starting. In Part A of this investigation, you will use photographs and illustrations of an earthworm to see how to use the taxonomic Key . In Part B, you will use the taxonomic Key to identify a living earthworm.

• <online photographs> of the earthworm called Aporrectodea tuberculata
• Key to Reproductively Mature Earthworms Found in Canada
• General Earthworm Diagram
• Earthworm Size Chart

1. Study the Key to Reproductively Mature Earthworms Found in Canada. You will notice that it has a number of branches. Each branch is based on a particular physical characteristic of earthworms. Find the characteristic called Body Size. You will see that there are three different sizes of earthworms in Canada ® Small, Medium, and Large.
2. You will also notice some terms that were introduced in Investigation #1. Look at the General Earthworm Diagram and make sure you can find and describe the following structures:
   • clitellum
   • genital tumescence (GT)
   • tubercula pubertatis (TP)
3. Make a chart that includes the following:

   Feature	Part A Online Earthworm	Part B Living Earthworm
   Body Size
   Body Colour
   Distance between nose and clitellum
   Description of GT
   Description of TP
   Shape and colour of tail region
   Scientific name (Genus and species)

   
   
   
4. Finally, you will see some Latin words such as Lumbricus terrestris and Aporrectodea trapezoides. These are the scientific names of two species of earthworms found in Canada. These are the names that you will record on your data chart. You will always have the Key so do not memorize these names. For practice, list the scientific names of all the earthworms found on the Key .
   
   

Part A: The Online Worm

Hint: Write down each step that you follow as you go through the Key.

1. Find the photograph that shows an earthworm on the Earthworm Size Chart. You will notice that the worm has been allowed to freely extend itself as though it was crawling. Is it a Small, Medium, or Large earthworm?

   This species of earthworm is considered to be Large. (Hint: Write this down in your notebook)

2. Locate the Large worms on the right side of the Key . You do not have to worry about the small or medium worms.

   
   

   
   

3. The next physical characteristic is the Colour of the earthworm. Does this worm Dark Brown-Black, or a Red-Violet colour? Or, does this earthworm have another colour?

   This species of worm is described as having Other Colour(s). Find this branch on the Key . (Hint: Write this down in your notebook)

   
   

   
   

4. Next, you have to determine the distance between the nose and the start of the clitellum. Look at the photograph. Is the distance between the nose and the clitellum greater than one centimetre? Or, is the distance between the nose and the clitellum less than one centimetre?

   In this species, the distance is greater than one centimetre from the nose to the start of the clitellum. (Hint: Write this down in your notebook)

   [Illustration of A. tuberculata as shown on the poster. Showing the ventral surface of the Aporrectodea tuberculata. Clearly showing pattern of GT and TP (file Aporrectodea tuberculata, this is an illustration from the poster) ]

5. Locate the genital tumescences (GT) on the ventral side of the earthworm.
   1. Are the GT found inside or outside the clitellum?
   2. Are the GT found on alternating segments?

   In this species of earthworm, the GT are found on alternating segments inside the clitellum. (Hint: Write this down in your notebook)

6. Locate the tubercula pubertatis (TP).
   1. Are the long and narrow?
   2. Are they triangular and look like pyramids?
   3. Are they sucker-like?
   4. Are the GT not visible?

   In this species, the TP are triangular and look like pyramids with their points facing into the non-GT segments. (Hint: Write this down in your notebook) The TP can be difficult to see on some species, with many common earthworm species the pattern of GT within the clitellum is the key identifying feature.
   
   

7. If you followed the steps in the Key , you should have discovered that this earthworm was an Aporrectodea tuberculata. Go to the Field Guide to learn more about this species of earthworm. (Hint: Write this down in your notebook)
   
   
8. If you did not identify this earthworm correctly, go back and try again.
   
   
9. If you have a Worm Watch poster from the Canadian Nature Federation (CNF) practice identifying the earthworms on the poster. Hint: The description of each earthworm on the poster follows the steps on the Key .

Part B. Identifying a Living Earthworm

• 1 reproductively mature earthworm
• 2 wet paper towels
• hand lens (optional)
• Key to Reproductively Mature Earthworms Found in Canada
• General Earthworm Diagram
• Earthworm Size Chart

Caution:

Handle earthworms with care and respect. Keep the earthworms between the two wet paper towels throughout the investigation. Earthworms need to stay moist and out of direct light.

What To Do

1. Gather all of the materials that you will need to complete this investigation.
2. Observe your earthworm and record your observations in your notebook.
   1. Describe at the colour of the earthworm.
   2. Describe the shape of the clitellum
   3. The location of the clitellum with respect to the head end of the worm.
   4. Describe the location and pattern genital tumescences (GT).
   5. Describe the general shape of the tubercula pubertatis (TP), if you can see it clearly.
   6. Describe the tail end of the earthworm and its colour and shape.
3. Follow the Key to Reproductively Mature Earthworms Found in Canada.

   Hint: Write down each step that you follow as you go through the Key .

   1. Is the earthworm Large, Medium, or Small? Place the earthworm on the diagram called Earthworm Size Chart. To determine the length of your earthworm, allow the worm to freely extend itself as if it was crawling. Measure the maximum distance the earthworm covers when completely stretched out. (Hint: Write this down in your notebook)
   2. Return the worm to the wet paper towels as soon as possible.

      Caution:
      At no time should you manually stretch out the earthworm. This kind of stress can seriously damage the earthworm.

   3. Determine the Colour of your earthworm. Remember that you only deal with this part of the Key and ignore the rest for the time being. (Hint: Write this down in your notebook)
   4. Follow the lines on the Key until you determine the scientific name of your earthworm. Use the illustrations and descriptions on the Key as a guide until you have identified your worm. (Hint: Write the steps down in your notebook)
   5. It is time to verify your identification. Gather all of the evidence to support your conclusion. Present your evidence to the class.
4. Return your earthworm to its habitat. CAUTION: Do not put "store-bought" worms into your garden or school yard. It is best not to risk introducing exotic earthworm species into new areas. As a challenge activity write-down all the exotic insects, plants, fish, birds and animals that have been introduced to your area and describe how they have affected the landscape, other species, and human activities.
5. Wash your hands.
6. Go to the for more information on your species.

What Did You Discover

1. 1. List the physical characteristics that are used to identify earthworms. What do you think are the most important features that you used to identify your worm?
2. 2. Draw a scientific diagram of the dorsal side of your living earthworm. Emphasize the following:
   • size of worm
   • body colour
   • distance of the clitellum from the head
   • shape and colour of the clitellum
   • shape and colour of the tail
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
3. 3. Label the following diagrams using the terms genital tumescence (GT), tubercula putbertatis (TP), and clitellum:
   
   
   Aporrectodea turgida
   
   
   
   Lumbricus rubellus
   
   
4. 4. Draw a scientific diagram of the ventral surface of your earthworm similar to the ones shown above. Ensure that you show the location and pattern of the GT, the shape of the TP, and the shape of the clitellum.
   
   
5. 5. Why do scientists use scientific names rather than the common names of living things?