Using Sea Urchins as a Bioassay

	by:                  Norm Dahm      Bill Johnson     Melinda Miller   Karen Shrader    Laura Parker  Email us by clicking on our names

• Systems, order, and organization
• Form and function
• Evolution and equilibrium
• Behavior of organisms
• Interdependence of organisms
• Biological evolution
• Use of various technologies in the classroom

Table of Contents:

Summary/Abstract

Instructor's Objectives

Target Age or Ability Group Audience

Teacher Instructions/Special Precautions

Materials & Equipment Needs

Background  [Prior Knowledge or vocabulary necessary to complete activity]

The Student Lab

Method of Evaluation/Assessment

Extension/Reinforcement/Additional Ideas

References Including Web Addresses

National Science Education Standards

Summary/Abstract  to top

In the background section of this activity, students will observe how to spawn male and female pencil sea urchins, Eucidaris tribuloides, or white sea urchins, Lytichinus variegatus. The students will then mix together the sperm and ova from the live sea urchins to observe and record the events occurring in the control and experimental groups for fertilization and development over a 2-5 day period. In the main student experiment, students will investigate the use of fertilized sea urchin's ova as a bioassay for differing pH levels between 3.4-7.2 to simulate what effects environmental pollution (i.e. acid rain) has on embryonic development.  These activities will allow students to emphasize critical thinking skills to examine organisms used in research and environmental concerns.

Key Words:  sea urchin, bioassay, inquiry, gametes, fertilization, embryology, pH,

•    Students will apply their knowledge of fertilization to spawning sea urchins.
•   Students will observe and measure events associated with the fertilization of sea urchin

  eggs and their development.
•   Students will understand the processes and major changes that occur with fertilization,

  cleavage, and the embryological stages of development.
•   Students will design and complete their own experiment using sea urchins as a bioassay

  in determining the effect of varying pH on development and mortality rates.
•   Students will use use a variety of technologies to relate how sea urchins can be used as a

  bioassay for environmental issues.

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• Grades:  9-12
• Classes: Biology I, Advanced Biology, AP Biology,  Human Anatomy and Physiology, Zoology, Environmental Science, and Marine Biology

Notes to the Teacher:  to top

 

Timing of this laboratory is extremely critical and may be different for each species and at different temperatures. This laboratory is ideally done over a period of one week.  Longer lab periods are ideal, but this lab could be accomplished in 30-40 minute time frames. Click here for an example of development times and stages.

If fresh sea water is not available for the lab, an alternative would be to use Instant Ocean or make artificial sea water.

Temperature requirements for species of sea urchins may differ.  Click here for more information.

Procedures for spawning male and female sea urchins can be accessed by clicking here (for animated graphics) or for written protocol, click here.

For protocol on storing the male and female sea urchin gametes, click here.

The protocol for making all the pH solutions used in this laboratory, can be accessed here.

If sea urchins will be kept for an extended period of time, you can feed them seaweed, carrots, potatoes, or Sea Urchin Cookies.  Click here for cookie recipe.

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Materials & Equipment Needs to top
 

Urchin Kit which consists of:

 
    0.5M potassium chloride solution (3.7 grams of KCl in 100 ml of distilled water)
    sea water, "Instant Ocean", or artificial sea water
    fertile male and female sea urchins
    1-5cc syringe with #25-#30 needle
    plastic or glass pasteur pipettes or eyedroppers
    small tubes to store sperm (micro-centrifuge tubes work great)
    beakers a little smaller in diameter than the diameter of female urchins
 
Note: if possible use glassware that has never been exposed to soap or detergent as this may disrupt development.
 
• pH solutions (click here for the solution protocol)
• Computer to show animation
• Microscopes with optional video microscopy setup (Flex Cam) and Snappy Cam software and hardware
• Refrigerator for egg storage (if needed)
• pH paper or pH meter
• magnetic stir bar
• magnetic stir plate
• 500 mL beaker
• distilled water
• hydrochloric acid
• 60 mL bottles
• thermometer

Background to top

 
•  Bioassay Background

    Bioassays are one of the important research tools for scientists all over the world.  A bioassay is an experimental method for determining the influence of an environmental component on an organism.  The environmental component that is studied must be quantified or measured before the tests may begin.  Usually small increments of measurements are used and a scale is developed. Inferences are drawn from the results of the bioassay and used to predict the effects of the environmental component on other organisms and populations.  Within this experiment the pH range will vary from 3.4 to 7.2 with  0.2 increments. The term pH is defined as the concentration of hydrogen ions in solution.  The greater the number of hydrogen ions, the lower the pH value.
     Bioassays come in many shapes and forms, they are usually carried out in a laboratory setting to minimize outside interference.  Many types of organisms are used for bioassays, but animals are the most common.  Usually the species, class, and age of the experimental animal should be the same as the animals to which the data will be applied.  Bioassays don't always involve live animals but some type of biological system must be used such as tissue cultures or cells.
    The sea urchin is the animal of choice for this experiment. The idea of developing bioassays using sea urchins is to show how living organisms can be used to set quality standards.   Specifically the mortality and mitotic rates will be observed and measured.  Sea urchins produce a prodigious number of hardy gametes and can be easily seen with naked eye.  There are many studies using sea urchins in bioassays, but the studies tend to gravitate around the effects of heavy metals and increased pH on embryonic development.
   The Environmental Protection Agency (EPA) has developed many types of bioassays to set quality standards, but there have been few bioassays that determine long-term effects of survival, growth and embryological development.  We hope that students may use this format to develop their own strategies for bioassays.
 

Prior Knowledge and Vocabulary Terms- Click Here


 

Anticipated questions from students:

1.  What is a bioassay?
2.  Why would we want to use sea urchins when we live in the midwest (or any other area without marine life)?
3.  Where do sea urchins live?
4.  Do we have to have increments that are so small?  i.e. 0.2 for pH
5.  Would temperature affect the sea urchins?
6.  What organisms could you use for studying pH affects in a freshwater environment?
7.  How are the eggs and sperm of the sea urchins compare to humans?

 
 
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The Student Lab to top

Introduction:

 
    In this lab you will be manipulating conditions which will change development of a sea urchin zygote.  Sea Urchins are in the phylum Echinodermata "spiny skin", class Echinoidea which are marine deuterostomes.  A deuterostome is an organism which undergoes radial cleavage during gastrulation.  Humans are also deuterostomes.  Sea urchin gametes are relatively the same size as human gametes.  While working with sea urchin gametes you can easily imagine what the fertilization of a human egg would look like!   Click here to see drawings of sperm and egg cells of sea urchins and humans.

 
Purpose:
 
Students will role play as EPA agents and develop a bioassay which will monitor water quality in a marine ecosystem using sea urchins.
 
Equipment:
 

Urchin Kit which consists of:

 
        0.5M potassium chloride solution (3.7 grams of KCl in 100 ml of distilled water)
        sea water, "Instant Ocean", or artificial sea water
        fertile male and female sea urchins
        1-5cc syringe with #25-#30 needle
        plastic or glass pasteur pipettes or eyedroppers
        small tubes to store sperm (micro-centrifuge tubes work great)
        beakers a little smaller in diameter than the diameter of female urchins
 
Note: if possible use glassware that has never been exposed to soap or detergent as this may disrupt development.
 

Computer to show animation

Microscopes with optional video microscopy setup (Flex Cam)

Refrigerator for egg storage

pH paper or pH meter

pH solutions

magnetic stir bar

magnetic stir plate

500 mL beaker

distilled water

hydrochloric acid

60 mL bottles

thermometer

 

Procedure:
 
 *   You will duplicate the teacher's correct technique for fertilizing sea urchin gametes. Click here.
 
*     After your teacher has demonstrated the correct procedure for fertilizing your sea urchin gametes you are to develop your own experiment.  Be sure to obtain teacher approval before you begin the bioassay.  Use the following questions to get started.  The experimental design is not to answer the following questions solely, they are to guide you through the process.  It is okay for different groups to have different designs!

  * Suggested questions to help formulate experimental design:
 
      1. How many organisms will you work with?
      2. How many control/experimental groups will you have?
      3. What are you trying to accomplish?
      4. What is at stake here?
      5. How may variables will you have?
      6. How will you measure your results?
      7. Is your experiment feasible considering the equipment available?
      8. How long will your experiment run?
      9. What are some hypotheses you can formulate regarding change in pH and sea urchin
          mortality and mitotic activity?
     10. What are some practical applications of your results?  Who would be interested in
           the results?
 
  Observations:
 
How will you observe and measure the test subjects? Microscope? Magnifying glass? Video Cam? Count the cells? What time schedule based on background information will your group use to view the developmental movement of your cell(s)?
  Example of the Observations obtained from students.
                                          (used with permission, Stanford Sea Urchin Site)
 

Conclusions:

   1. What inferences can be drawn from the results?
   2. What extrapolations can be derived and used in real world situations?
   3. How do you know the results are authentic?  Did you make the experiment repeatable?
   4. What other environmental components could be used for further study?
   5. Were any of your hypotheses wrong? ( In research it's okay to be wrong)  How would you
       rewrite the hypotheses in light
        of your results?
   6.  If you wanted to study pH and environmental concerns in a freshwater system, what species
        of organism could be used as a bioassay?
 
 
***  Remember: " The facts drive the hypotheses, the hypotheses never drive the facts!"
     ...Sherlock Holmes.
 

Methods of Evaluation/Assessment to top

 

Laboratory Report:  Students will submit a written laboratory report which follows the scientific method and includes pictures, either from video, SnappyCam, or hand drawn to show the processes associated with development.

Students will submit a portfolio of background research, drawings, or electronic pictures, and their findings as an EPA agent. This can be done in written or electronic form ( for example- Power Point)

Written paper/pencil test or assessment

Extension/Reinforcement/Additional Ideas to top

 

Do nitrate concentrations associated with run off pollution affect the developmental process of fertilized sea urchin ova?

What effect does thermal heating from cooling towers have on the  the developmental process of fertilized sea urchin ova?

What are the effects of heavy metals (for example mercury) on development and mortality of sea urchin ova?

 In what other ways do environmental companies and agencies use sea urchins as bioassays?

 Teachers may also want to show students the similarities in the size of the human and sea urchin gametes.

 Teachers can also extend this activity to be used in freshwater system, zebrafish can be used for this activity.

 Teachers can also expose the students to the culinary delicacy of uni, sea urchin eggs for their tasting.

References Including Web Addresses to top

Investigating and Modeling Sea Urchin Fertilization and Development (http://www.woodrow.org/teachers/biology/institutes/1997/urchin/)by Rick Piercy and Alisa Poppen.  This site from the Woodrow Wilson 1997 Biology Institute contains activities and background information on sea urchin embryology.

Sea Urchin Embryology a Genetic Approach to Development(http://www.woodrow.org/teachers/biology/institutes/1994/sea_urchin_embryology.html)by Mary Petti and Susan Terry.  This site from Woodrow Wilson 1994 Biology Institute contains an activity for gene regulation in sea urchin development.

Stanford Sea Urchin Education Site(http://www-leland.stanford.edu/group/Urchin)  An EXCELLENT site for any background information on sea urchin fertilization and development.  A great site for teachers who need lab activities, animation, overheads, video clips, and current research on sea urchin embryology.  A wealth of information on sea urchins and embryology.

Dr. David Epel's research site(http://www-marine.stanford.edu/HMSweb/Epel.html) has many research articles concerning sea urchin research, such as The hierarchy of requirements for an elevated pH during early development of sea urchin embryos, Cell 40:657-666.

Urchin Web's(http://207.62.132.224/urchin/urchinweb.html) goal is to provide information and sources on sea urchins as research organisms.

Your Connection to the Animal Rights Movement(http://arrs.envirolink.org/Q79.html) has information on the bioethics of using animals in the laboratory.

EPA Reference Site(http://www.epa.gov) has resources on using sea urchins as bioassays.