Grunion Eggs Aron Rudnick

Title: Hatching Grunion Eggs

Principles Investigated:

1) Process of external fertilization

2) How spawning patterns correlate to lunar cycles.

3) How the reproductive behavior of animals allows for greater success passing on genes.

4) How kinetic energy stimulates hatching.

Standards : MS. LS1.B Animals engage in characteristic behaviors that increase the odds of reproduction.

Materials: 1)Grunion eggs in the sand (may be acquired at Cabrillo Marine Museum)

2)Clear plastic cups

3)1 Gallon Seawater, (from Pacific Ocean)

Procedure: Place a tea spoon of sand with grunion eggs in the clear plastic cups. Next, mix with a half cup of seawater in each cup(gently poured). Wait to settle. Shake the cup gently assuring that water does not splash over for 6 seconds. Observe how eggs separate from sand. Wait until eggs hatch.

Student prior knowledge: Grunion(Leuresthes tenuis) are members of the New World silverside family, Atheriniosipidae. They are found between Monterey, California and Baja California. They are non-migratory and inhabit the near shore at depths approximately 60 feet deep. In the spring and early summer about four nights around new and full moons they spawn by a curious practice of coming ashore with the evening high tides. The females make little holes in the wet sand to lay their eggs and the males flop around for the chance to deposit ejaculate in the holes.

Explanation:

The purpose of this demonstration is to simulate the natural processes that stimulate the hatching of grunion eggs in the wild. The egg embedded sand should be procured at a time to approximate two weeks from when they were laid. This is roughly the amount of time for gestation in the wild. Be sure to check with your grunion egg provider that the timing is correct. The shaking of the water simulate the movement of tides coming in. The kinetic energy of the turbulent water separates the eggs from the sand and stimulates hatching. Under natural conditions the grunion fries would be swept back into the open ocean.

Questions & Answers:

Why might laying eggs in the sand be a successful reproductive strategy? By having the grunion eggs deposited in the sand as opposed to being let loose in the open water, they are protected from other organisms that might feed on the eggs and the turbulence of ocean currents.

What other animals have reproductive cycles that occur in relation to lunar cycles? Insects, birds, fish and humans are among other types of animals that appear to have reproductive cycles related to lunar cycles.

What is external fertilization? It is the process by which eggs and sperm are released and fertilization takes place outside the organisms. Otherwise known as spawning, it is practiced by frogs and most fish.

Applications to Everyday Life:

Some research show a positive correlation between lunar cycles and the release of hormones having to do with reproduction. Among mammals, female menstruation often corresponds to lunar cycles. Fisheries can also be better maintained when lunar related reproductive cycles are taken into account.

On Lunar cycles having an effect on reproduction:

http://www.ncbi.nlm.nih.gov/pubmed/16407788

On Grunion:

www.dfg.ca.gov/marine/gruschd.asp