Toxicology and Environmental Assessment with California Blackworms

Author: Karen Munroe
Adapted for PULSE by: Patricia Wheeler
Editor: Stephanie Nardei


Two Class Periods (2.5 hours)


30 minutes


 4 400 ml Beakers
Graduated cylinders (10 ml and 5 ml)
California Blackworms* (1 oz. per class)
Distilled water or tap water that has been set-out for at least 24 hours (approx. 2 gallons per class)
Bottle of Vodka

River Picture Overhead
Handout 1
Handout 2
Handout 3
Handout 4
Handout 5
Each student group:

  1. 50ml graduated cylinder
  2. 9 plastic weigh boats (2/treatment and one with original worms in water)
  3. Pencil or grease pencil
  4. 4 spoons or 4 pipettes
  5. Clock with a way to count seconds
  6. Sheet with places for observations during experiment and for recovery

Experiment Handouts

*Need to order California Blackworms from an aquatic food supplier.

This lesson uses mystery to capture student interest.  Students will investigate the potential toxicity of water samples using *California Blackworms.  This lab emphasizes experimental design and application of principles in the science of toxicology, such as dose-response, routes of entry, acute versus chronic, and exposure concentration.  The sophistication level of this activity is increased if the students are expected to conduct and evaluate their experiments with minimal guidance from the teacher. 

Students will be able to:

  • Apply knowledge of toxicology for an environmental study.
  • Make inferences regarding the level of toxicity in each water sample.
  • Create a dose-response graph.

National Science Education Standard
Content Standard A – Science as Inquiry

  • Identify questions and concepts that guide scientific investigations
  • Formulate and revise scientific explanations and models using logic and evidence
  • Communicate and defend a scientific argument

Content Standard F- Science in Personal and Social Perspectives
Personal and community health

Arizona Science Education Standards:
Concept 1: Observations, Questions, and Hypotheses

  • PO 2. Develop questions from observations that transition into testable hypotheses.
  • PO 3. Formulate a testable hypothesis.

Concept 2: Scientific Testing (Investigating and Modeling)

  • PO 1. Demonstrate safe and ethical procedures (e.g., use and care of technology, materials, organisms) and behavior in all science inquiry.
  • PO 4. Conduct a scientific investigation that is based on research design.
  • PO 5. Record observations, notes, sketches, questions, and ideas using tools such as journals, charts, graphs, and computers.

Concept 3: Analysis, Conclusions, and Refinements

  • PO 2. Evaluate whether investigational data support or do not support the proposed hypothesis.

Concept 4: Communication

  • PO 2. Produce graphs that communicate data. (See MHS-S2C1-02)
  • PO 3. Communicate results clearly and logically.
  • PO 4. Support conclusions with logical scientific arguments.

Teacher Background
See Basic Toxicology under the Environmental Health Resources section of PULSE:http://pulse.pharmacy.arizona.edu/resources/toxicology/teachers.htm

Related and Resource Websites
Chemicals, the environment and you http://science.education.nih.gov/supplements/nih2/chemicals/default.htm
HOPE Lesson Plan & Activity: http://coep.pharmacy.arizona.edu/curriculum/blackworms/index.html
Obtain Free Blackworms: http://aquaticfoods.com/intros.html
California Blackworms: http://www.wormman.com/pd_california.cfm
Toxicants and Worms: http://www.terrificscience.org/freeresources/lessonpdfs/Toxicants_and_Worms.pdf
Environmental health lessons from NIEHS: http://www.niehs.nih.gov/science-education/scientists/classroom.htm
Discussion Forum on California Blackworms: http://www.awforum.net/discus/topic.asp?TOPIC_ID=130
EHP Lesson Plan on Blackworms: http://www.ehponline.org/science-ed/2007/chlorine.pdf
Critter Page: http://members.aol.com/larval1/critters.htm


Day One
Before beginning the presentation with students, set up a table with at least two replicates of each of the dilutions used in the Blackworm lab (10%, 2.5%, 0.25% and 0% alcohol).  The students will know they are of various contamination concentrations, but do not indicate which is which.  Instead, label them A, B, C and D according to where you will associate the “source” of each concentration level on the map (see map)


  2A 3B 4C 5D
Teacher Information Only:
Please notice concentrations are not in order

Give the students the following story:

Ask if they have ever heard of canaries being brought into mines with miners.  Let them know that the miners brought the canaries in with them because the canaries were more sensitive to changes in the air quality than the miners were, and if the canary started to seem sick or even died, it was a signal to the miners that they needed to get out of the shaft where they were.  Lots of different things are used as indicators- and in this scenario, use California blackworms as indicators- not of air, but of water quality.

You can give them some background on the blackworms- lots of interesting information is available at: http://en.wikipedia.org/wiki/California_blackworm

Give the scenario.  “We have sampled water from a stream along the banks of a river where there is a suspected contamination.  Water has been sampled from the points shown along this stream (show picture) and we are going to use the California blackworms to tell us something about the quality of the water from each site.  While we might not necessarily want to drink water from a place that can sustain worms, we most definitely do not want to drink from a place that has a negative effect on these worms.  What we want to do is take a look at what the natural behavior of the worms and then compare how the worms behave in each of the different samples.”


There is a great opportunity to talk about what a control is, as well as a qualitative measure versus a quantitative one.  All you expect the students to do here is to make qualitative observations and inferences. 

4. Now put the worms into each of the treatments, asking students to observe what happens and discuss while you continue to place the worms in each treatment.

5. Once the worms are all placed in the treatments, ask the students to guess which of the treatments might be considered control, low concentration toxin, medium concentration toxin, and high concentration toxin.  Ask for a show of hands and record their responses on an overhead:


























6. Discuss the responses and why it is that each was chosen.  Perhaps make some observations and write them beneath each lettered column.

7. Then get an idea of what the students know about dilutions.  Give them the following picture and have them tell you which they would consider the control, low concentration, medium concentration, and high concentration of toxin.  Ask what the final volume is of each one as well.  It is important that they realize that this is the reason it is easy to compare the concentrations.

8. Have the students solve for each toxin concentration level by displaying the following table on an overhead or on the board:






% of Toxin

ml Toxin

ml H2O







% of Toxin





ml Toxin





ml H2O





8. Wrap-up:

    1. Students reflect in their science journals about the experimental design modeled/discussed during this discussion.
    1. Students reflect on their feelings for using live organisms for the purpose of an experiment.  Are their options?  How could options be implemented?
    1. Students could begin working on Handout 1: Blackworm Lab in preparation for the experiment.  Note: If time is an issue or you think the students might need some extra help with designing their own experimental design, this is the suggested wrap-up to assure the following day students will be ready to simply begin their experiments. 


Day Two

  1. Describe to the students their objective as researchers, “In the experiment, you will explore whether the inferences you made during the mystery yesterday were correct.  Do the worms behave in the control, low, medium and high concentrations like you decided they did?  How you would test this?”  They should get the idea that they will try different concentrations of toxin and see how the worms behave in each one.  They will make objective observations of how the worms behave normally, allow the worms to acclimate to their control environment (100% water), and then observe how the behavior changes in each treatment. 
  1. Provide the dilutions to the students - having multiple containers of each concentration makes this easier for large groups.  The students receive the following:
      • 50ml graduated cylinder
      • 9 plastic weigh boats (2/treatment and an extra one as a way to carry the worms to the work area)
      • Pencil or grease pencil
      • 4 spoons or 4 plastic pipettes
      • Clock with a way to count seconds
      • Experiment Handouts (1-6)

  2. Each group will label their weigh boats in pairs- a water and a treatment for each (the students will place the worms from the provided weigh boat into four different water filled boats, one per treatment).  Then will fill the boats with appropriate solutions:

Treatment 1: one boat with water and one with control (also water)
Treatment 2: one boat with water and one with low concentration (0.25%)
Treatment 3: one boat with water and one with medium concentration (2.5%)
Treatment 4: one boat with water and one with high concentration (10%)
(**Have students think about the order they want to transfer solutions so as not to contaminate each with the other…students can come up with the appropriate order on their own- and if they don’t do it correctly, just make sure they think about what sort of effect the incorrect order might have)

  1. Students will transfer the worms from a provided weigh boat into each of the water solutions.  While allowing the worms to acclimate for 2-3 minutes the students will take notes as to the normal behavior of the worms.   They may just observe, or see how the worms react to different perturbations (probing, swirling, etc.).
  1. After 2-3 minutes, the students can take each and transfer it to the treatment boats.  They will take initial observations at 0 minutes, and then again at 3, 6, and 10 minutes.  For each time point they will take both notes and make an activity assessment.  Activity runs from 0 (no movement), to 2 (normal movement) to 4 (hyperactive).
  1. At the end of the experiment, have them transfer the worms to the original water controls for each of the treatments and watch how the worms recover.  This part can either be extended to talk about what it means, or the lab can end here. 
  1. Have the students clean up their areas and complete the “Reflection Handouts” (5 & 6). If the students worked on the experiments up until the end of class, the Reflection Handouts could be homework. They should be completed before the experiment is discussed as a class.

Day Three

  1. Ask the students how their inferences in the mystery compared with their experimental results.  Were they the same?  If so, what in their prior experience allowed them to correctly identify each toxicity level?  Different?  If so, what made them reconsider their original prediction?
  1. Now the big wrap-up… Put the picture of the river back up.  Split the students into two groups and have each group come up with where each sample was taken and where the contamination event might have occurred.  Have a representative from each group report for each group- presenting their solution and the reasons why they chose that solution.  You can talk about stories that could explain the contamination, such as an industrial plant, for example, on the river bank at location “B”.  Students seem to have an intuitive sense of the dilution effect that can happen downstream- so this might be a good thing to bring up.
  2. You can also follow up with identifying all of the abstract concepts from the initial presentation with what would be an example of each in the mystery and experiment.
  1. Ask students how they might do an extension of this original experiment.  Could we change a variable to learn something else about the water or blackworms?  Remind them of principles such as, exposure frequency and duration.

Not Applicable.

Embedded Assessment
Assess students’ ability to form and evaluate a hypothesis.

Assess students’ ability to evaluate their data and determine if it does or does not support their proposed hypothesis.



PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:

NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award


Supported by NIEHS grant # ES06694

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Last update: August 2, 2007
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