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no eggs and/or no sperm

ALTERNATIVE LABS

NO EGGS

You have spawned all of your sea urchins and though you did get some sperm, you were unable to get any eggs.

  • See SPERM EXPERIMENTS for ideas on how to use the sperm in experiments. This need not be done the same day, as sperm will keep up to a week in the refrigerator at 4-5 C

NO SPERM

  • See ARTIFICIAL ACTIVATION. Eggs can be activated without sperm to show some of the early events of development [Fertilization membrane, nuclear centering, and nuclear envelope breakdown]. Full development will not occur however.

NO EGGS OR SPERM

  • In advance, order commercial slide preparations of the various stages of development. These are available through numerous suppliers. Even a single slide of each stage is enough if projected using the microvideo camera, microscope and monitor.
  • A great deal about the anatomy, physiology, and natural history of sea urchins can be done. We highly recommend a dissection of the sea urchin. See "half shell"

NO SEA URCHINS!

PREVENTING THIS IN THE FUTURE

In biology it is almost impossible to prevent all possible problems. That's life! Here are some ideas to help out.

  • Young embryos can be preserved quite easily for months, if not years.
    • To an active culture of embryos at the stage you wish to preserve, add a 10% volume of 37% formaldehyde solution [Carcinogenic! Toxic!].
    • You need only preserve a small volume in a tightly capped vial.
    • Keep these preserved specimens in a refrigerator till needed.
    • LABEL PROPERLY, including the words TOXIC CARCINOGEN on the vial.
    • In this way, the following year, if you run into trouble, you can show examples of embryos at various stages.
  • If you do not allow your students to handle material fixed in formaldehyde you can replace the formaldehyde from above with alcohol.
    • Using denatured alcohol, make up a dilution series of 30%, 40%, 50%, 60% and 70% alcohol in distilled water.
    • Remove as much of the now 3.7% formaldehyde solution, as you can without exposing the embryos to air.
    • Add the first solution of 30% alcohol. Let the embryos sit in and settle in this solution for 15 minutes.
    • Repeat with each successive solution until the embryos are in 70% alcohol.
    • These can also be kept in the refrigerator for quite some time. [70% alcohol is flammable, barely, so use due caution]
  • A less permanent method, is to fix with formaldehyde as in above.
    • Remove the formaldehyde as with alcohol dehydration above.
    • Re-suspend in 1 M glycerol [9.2% glycerol in distilled water] instead of the alcohol series.
    • Store in refrigerator also.
  • Lastly, be sure to order sea urchins you know are in season and plan your sea urchin lab for when the sea urchins are in season. Storms can come up, preventing your company of choice from going out collecting, but usually they will have a stock of some kind in reserve, just for this kind of situation.

$COST$

  • If you live near the ocean, consider getting a collecting permit (often through your state's fish & game department) and going out yourself.
  • Calling friends near the ocean. Often knowledgeable teenagers or young adults are interesting in a little extra $, but at a rate lower than the commercial places. MAKE SURE THEY HAVE A VALID PERMIT or a FISHING LICENSE that allows collecting sea urchins.
  • Share sea urchins with other teachers at your school or neighboring school(s).
  • You can order fewer sea urchins and take your chances, but I would not order less than five. Not every period needs to see spawning. It can be simulated for the later periods. Do save some fertilized embryos from pervious periods for those later in the day. Using the Egg and Sperm Storage techniques, you can often extend the use of eggs and sperm out for up to a week, allowing for many labs and experiments.