Sea Urchin Embryology Back to Contents page






Urchin does not spawn

Injection of potassium chloride solution into the mouth instead of the body cavity will not induce spawning. See images in CORE lab. The urchin may be empty, because it has already been spawned (in lab or field), or out of season. The potassium chloride may be the wrong concentration. Try making it again.

No males or no females

We recommend purchasing 10 sea urchins to help improve the odds of getting at least one of each, but even then, it is still possible to get all of one or the other. (99% in favor)

Eggs are already fertilized

Getting ANY sperm into the egg beaker before you want to will fertilize the eggs (often a problem when students switch eye droppers). Try setting the eggs and sperm on opposite sides of the room.

Eggs disintegrating

Using fresh water instead of seawater to make dilutions.

Even a small amount of detergent left in glassware can cause problems.

Embryos did not develop

Polyspermy, or too warm or too cold for the species you are using.

Again, even a small amount of detergent residue on glassware can cause problems. Keep your "embryo" glassware separate and hand-wash. Using new glassware or disposable plastic cups will avoid this problem.

Is it an embryo? Students have been known to spend the entire period watching an air bubble.

Not enough time!

Timing is critical in these labs. Murphy's law applies here. Things can go wrong at the worst possible time.

See also Adults