CSU Monterey Bay - Kibak - BIO 310  

Determining Optimal Sperm Concentration for Toxicity BioAssay

  
 

 

What is the correct sperm dilution for urchin assay?  
     

Because sperm are very sensitive to a wide range of xenobiotics, and because they are quite easy to obtain from sea urchins, the Sea Urchin Sperm Toxicity Bioassay is one of the most common tests for contamination in the marine environment (and even in non-marine environments). A true toxicity assay that will stand up in court is a lengthy carefully controlled procedure that takes an experienced technician six to twelve hours to perform. Obviously we do not have that amount of time, so we will perform one of the key steps in the assay.

In this lab you will prepare a serial dilution of sea urchin sperm to determine the appropriate concentration for the fertilization assay. The overarching objective is simply to become familiar with critical life stage assays such as this one, where sea urchin sperm is incubated in a control solution of pure seawater and a test solution, and then the effect on fertilization is measured. Test waters that significantly lower the rate of fertilization are probably contaminated and warrant further testing. Because sea urchins are not domesticated and exhibit seasonal and individual variability in sperm activity and concentration, it is important to conduct this dilution test for each urchin one uses in an assay.

     
 
     
Write Up    
  1. Title as question.
  2. In other words: "At what dilution of sperm does fertilization begin to decline?"
  3. Methods - details on how you answered the question including:
    1. the details of the serial dilution,
    2. how you obtained the eggs and sperm,
    3. and how you evaluated the extent of fertilization.
  4. Data/Results - a table of results and a "dose-response" line graph of % fertilization as a function of sperm concentration. Hopefully you will have some information on polyspermy as well and a JPEG.
  5. Describe how you would prepare a control and test solution of these sperm in order to perform a critical life stage assay on cooling water from the Moss Landing Power Plant.

Other observations will depend upon what else we are able to accomplish.

 

Due April 6, 2006