Oyster Farming Simulation

Learning Target

• Investigate the technologies that have changed the way humans influence the inheritance of desired traits in organisms. 

Success Criteria

• Students gather information about a technology that has changed the way humans influence the inheritance of desired traits in oysters

• Students use their understanding of genes and heredity to identify ways in which humans influence the inheritance of organisms.

Questions to Ponder...

• What do you know about oysters?

• Many oyster populations are declining.  What would you do to help increase their numbers?

Oyster Farming Simulation

• In the Peppered Moth Simulation we observed how species can change as a result of changing conditions in their environment. When better adapted organisms out-compete other organisms it is often referred to as Natural Selection.

• In this next simulation we will look at how humans can have a direct affect on a species and whether they survive or not. This is called Selective Breeding.

Beleaguered by Disease

The wild oyster fishery, which has helped define a way of Life in the mid-Atlantic and Gulf Coast regions, saw the first signs of decline in 1956 when a mysterious parasite, referred to as MSX, killed more than 90 percent of the oysters in Delaware Bay. By the next year, MSX began making its way up the lower Chesapeake Bay, and over the next several years, it spread farther up the Bay into Maryland waters. 

Early in the 1940s oysters in Gulf Coast waters began dying as a result of contact with a parasite, Perkinsus marinus, (more familiarly known as Dermo which is short for Dermocystidium.) In the mid-80s, Dermo began killing oysters in the Chesapeake Bay – over the next decade, the parasite spread throughout the Chesapeake, sometimes mistakenly transported by programs and commercial operations that were meant to replenish oyster populations. By the early 90s, Dermo had infested virtually every major oyster bottom in the Bay. Dermo has continued to move up the Atlantic coast; it has struck Delaware Bay and been seen as far north as Maine oyster grounds. 

Much progress on understanding oysters has been made due to laws made by Congress in 1989 which caused the formation of the Oyster Disease Research Program (ODRP). ODRP has improved approaches to managing around the disease and has furthered the scientific understanding of the dynamics of disease. In addition, new ways have been created that will soon give East Coast oystermen a rapid way to test for threats of Dermo and MSX. 

Scientists have begun breeding oysters that are more tolerant of both MSX and Dermo. Using traditional breeding practices to spawn adult survivors of disease, researchers are developing strains of the eastern oyster that are hardier and more disease resistant. For the past several decades, scientists at the Rutgers Shellfish Lab have bred lines of oysters that would tolerate MSX. 

Then in 1992, Dermo invaded the Delaware Bay. The specially bred stocks for MSX had little resistance against this new parasite and were hard hit. Though many died, still there were some survivors. It is those survivors and their offspring that have been studied for developing oysters resistant to both MSX and Dermo. 

Scientists are using these dual disease resistant oysters in a regional project, the Cooperative Regional Oyster Selective Breeding program (CROSBreed) to evaluate the growth and survival of different oyster lines in the mid-Atlantic. 

Procedures

Round 1

1. Starting with 2 yellow and 2 blue oysters in your first generation, decide in your team what two oysters to breed first (yellow X yellow, yellow X blue, or blue X blue). 

2. Bring your two chosen “oysters” to the “breeding pond” and bring the offspring back to your “hatchery.” 

3. Record your results.

Round 2

1. After discussing the results of the round 1 decide as a group which two oysters to breed now.

2. Write your choice and prediction on a sticky note and go back to the pond.

3. Record your results.

Round 3-5

1. Follow Round 2 for generations 3-5.

Analysis

1. How many MSX resistant oysters (red) were you able to raise?

2. Which color oyster never produced any resistant offspring? 

3. Study the results of all the combinations.  Do you see a pattern?

Back to Teams...

• Discuss your predictions about what the results were going to be when you bred certain pairs.

• What kind of patterns do you see in the combinations?

• If you were able to predict the results of breeding how might this be helpful to your study of oysters?

• As a team discuss which trait may be dominant and which is recessive

Vocabulary to know...

• What does the word susceptibility mean?

Oyster Farming Simulation

Part 2 - Breeding Resistance

Introduction

• Now your oyster hatchery would like to try breeding oysters that are resistant to Dermo (Red; dd).  

• Having studied, you know a bit more about the dominant and recessive traits of the oysters on your farm:

  • • One strain of oysters carries two genes for Dermo susceptibility (DD).  

    • Another strain of oysters at your hatchery has one dominant gene for disease susceptibility and one recessive gene for disease resistance (Dd).  Your first attempt to breed a disease resistant oyster is by crossing the two strains, Yellow (DD) X Blue (Dd). 

Materials

• data table (see below)

• 2 yellow Lego pieces

• 2 blue Lego pieces

Procedures

1. Predict what your results will be, then go to the “breeding pond” to find out what offspring you get.

2. Try breeding different combinations of oysters for 5 generations, but each time your group decides what two oysters to crossbreed, make a prediction about the results.

3. Try every possible combination.

4. Procedures

Round 1

1. Starting with 2 yellow and 2 blue oysters in your first generation, decide in your team what two oysters to breed first (yellow X yellow, yellow X blue, or blue X blue). Write your choice and prediction on a sticky note.

2. Bring your two chosen “oysters” to the “breeding pond” and bring the offspring back to your “hatchery.” 

3. Record your results.

Round 2

1. After discussing the results of the round 1 decide as a group which two oysters to breed now.

2. Write your choice and prediction on a sticky note and go back to the pond.

3. Record your results.

Round 3-5

1. Follow Round 2 for generations 3-5.

Analysis

1. How many Dermo resistant oysters (dd) were you able to raise?

2. Which oyster strain never produced any resistant offspring?

3. Use Punnett Squares to explain the outcomes from your selective breeding.

Back to Teams...

1. What would you do to increase the oyster population in Chesapeake Bay?

2. How else do you think selective breeding is being used in the United States?

3. How is Selective Breeding different than Natural Selection?