## It’s time to think about crosses!

After my oysters are done conditioning, I will strip spawn them and rear larvae. Understanding which males and females to cross, and how many to use, are important to ensure genetic diversity in the F1 generation.

From each tank, I will pool eggs, but keep sperm separate. I will cross the pooled eggs from one tank with sperm from all males from all tanks. The next day, I will measure hatch success, then pool D-hinge larvae by treatment.

**Table 1**. Number of males available for crosses, assuming there is a 50/50 male-to-female ratio in each tank. Tanks 1-3 were exposed to low pH conditions, and tanks 4-6 had ambient water conditions. Number of oysters from each tank can be found here.

Tank |
Number of Males |
---|---|

1 |
9 |

2 |
9 |

3 |
7 |

4 |
8 |

5 |
9 |

6 |
8 |

Heat Shock |
6 |

Total |
56 |

With 56 males to cross and 7 different “tanks”, there are 392 possible crosses. If I were to limit the number of males used, I would have less crosses.

**Table 2**. Number of crosses for varying numbers of males used.

Number of Males |
Number of Crosses |
---|---|

1 | 49 |

2 | 98 |

3 | 147 |

4 | 196 |

5 | 245 |

After measuring hatch rate, I can pool my individual crosses into groups based on treatments.

**Table 3**. Treatment pool combinations. In total, there are nine possible pools.

Parent 1 |
Parent 2 |
---|---|

Low Female | Ambient Male |

Low Male | Ambient Female |

Low Female | Heat Shock Male |

Low Male | Heat Shock Female |

Ambient Female | Heat Shock Male |

Ambient Male | Heat Shock Female |

Low Female | Low Male |

Ambient Female | Ambient Male |

Heat Shock Female | Heat Shock Male |

Each pool will be transferred to 28 micron silos, so I will need replicates. Assuming I can fit four totes on each level of the table at Manchester, and each tote can fit 8 silos, I can have a maximum of 64 silos. The number of replicates I need will depend on how many larvae hatch and my stocking density. Molly recommends having 15-25 larvae per mL of silo volume.

**Table 4**. Number of silos needed based on replicates used for each pool.

Replicates |
Total Silos Needed |
---|---|

2 | 18 |

3 | 27 |

4 | 36 |

5 | 45 |

6 | 54 |

7 | 63 |

Here’s what I need to do next:

- Consult with Steven and Brent on the number of crosses, and where I can trim crosses
- Obtain drippers (1 L/hr drippers for first few days, 1 gallon/hr drippers for remainder of larval period
- Determine flow rate and pipe diameter needed for manifolds
- Build manifolds
- Ensure I have enough tubing to feed silos
- Find a method to volumetrically count eggs and sperm

from the responsible grad student http://ift.tt/2sq8IyL

via IFTTT