The storage of gametes is a "hot topic" in our news lately. From sperm banks to frozen embryos, how we view conception is changing. But what about the practical side of storing gametes from a useful animal? We have an opportunity to work this out for sea urchin.
Unlike, cows and sheep, where the techniques are well worked out, creatures that live in the sea are much harder to work with. The usual technique of freezing down with liquid nitrogen does not work because of the high osmolarity needed for a marine organism.
This is what we've worked out so far:
Eggs
- 30ug/ml of chloramphenicol (antibiotic). Make by dissolving 0.03g/liter of sea water. This is not the "best" method, but the easiest. Chloramphenicol is potentially cancer causing, use due care especially when weighing it out. In diluted, liquid form, it is less dangerous. Will work with most sea urchin species.
- 100ug/ml of ampicillin, sodium salt (antibiotic). Make by dissolving 0.1g/liter of sea water. Ampicillin works great with some species (L.pictus) and just OK with others (S.purpuratus), but is less toxic than chloramphenicol.
- The best method is rather involved (see Dr. Epel's protocol).
Sperm
- Store at 4C in a small closed tube, like a micro-centrifuge tube or small test tube with a good stopper. They can keep easily a few days this way. In a small container with less air space they can keep up to a week.
With luck, this means we can keep the gametes for a couple of weeks. That is not very long when you consider that human sperm, eggs and embryos can be kept for years.
This investigation is totally open ended. We do not know the answers. Suggestions for proceeding:
- Visit the library or the Internet and find out as much as you can about a) gametes b) gamete storage c) food storage and d) sea urchins and their environment.
- Using the above information brainstorm about possible ways to store the sea urchin gametes.
- Propose actual experiments that might be used to test some of your theories.
- Ones that are possible to do at your school, set up and try.
Lastly, report your findings in class and to us.