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Can the Heartbeat of a Chicken Embryo be Detected Without Breaking Its Eggshell?

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Author: Julianne Blair Bochinski

Note: It is recommended that this experiment be conducted under the supervision of a research scientist. The International Science and Engineering Fair has established strict guidelines to which all of its affiliate fairs must adhere. These guidelines involve experimentation with vertebrate animals. It is the responsibility of the student to follow those rules carefully. (See the Foreword and/or contact Science Service, the administrator of the ISEF, for a copy of the applicable rules.)

Purpose

To see if it is possible to measure the early heartbeat of a chicken embryo without breaking its eggshell or disturbing the chick's development—as other methods have done in the past.

Materials Needed

  • Zygo Axiom 200 interferometer
  • retroreflector and mount
  • VAX computer by Digital Equipment Co.
  • 3 3-day-old incubated fertile chicken eggs
  • 1 3-day-old dead chicken egg
  • incubator

Experiment

The movement within an eggshell will be measured with a Zygo Axiom 200 interferometer (which sends a light from a laser through a beam splitter that splits the light beam in halO. One half of that light will travel out to a fixed mirror and 190 bounce back. The other half will travel out to a movable mirror that is touching an egg, so that when its eggshell moves from the embryo's heartbeat, the mirror will also move. Therefore, the beam that will bounce off the movable mirror will have its phase altered in such a way that when it returns to the beam splitter (where it is combined with the other beam), constructive interference will result from the action of the waves joining in phases. Destructive interference will occur if the waves are out of phase. Then, the changes in the distance traveled by the beam going to the egg (in millionths of a millimeter) will be calculated from the patterns of light intensity. The experiment will be repeated on two more fertile embryos (to achieve consistent results) and on a dead embryo (as a control).

Procedure

  1. Obtain permission to work under the supervision of a research scientist, probably at a local university.
  2. Set up the Zygo Axiom 200 interferometer and the retroreflector and mount with your supervisor's assistance, and connect the apparatus to a VAX computer that will record the data of the changing phases of the beam.
  3. Obtain three fertile chicken eggs, together with a dead one (to serve as the control), all of which are about 3 days old. Store them in an incubator. Place one egg at a time gently up against the movable mirror on the retroreflector, and expose it to the light beam for 1½ minutes to collect shell vibrations as data points. Repeat the procedure again when the eggs are 4 and 5 days old .
  4. After the data points of the heartbeat frequencies have been sent to the VAX computer, they will be put onto a graph and analyzed as time versus displacement.
  5. After experimentation, observe the condition of the eggshells for cracks, and carefully observe the eggs until they hatch, to see if this method has disturbed the chicks' progress in any way.

Results

  1. According to your recorded data, what were the average beats per second in each embryo?
  2. Were the beats per second less detectable as the embryo matured? Why do you suppose this occurred?
  3. Did any of the eggshells crack as a result of experimentation? How long did it take before the eggs hatched? Were the chicks underdeveloped or harmed?
  4. What other applications could this method have in studying the development of embryos inside shells?
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