Development and hatching of fertilized eggs

Approximately one and a half hours after fertilization, eggs enter the 2-cell stage and blastomeres can be observed under a microscope.

As cleavage progresses, eggs form a mulberry-like mass, which is called the morula stage.

The embryo is formed to hold the egg yolk and oil droplet approximately one day after fertilization, followed by the hatching of the larvae from the egg in 15–20 hours.

The fertilization rate is calculated by observing the artificially inseminated eggs under a microscope and excluding those that do not show the formation of an egg membrane or cleavage over time.

Fertilization rate (%) = number of eggs fertilized normally / number of eggs artificially inseminated x 100

The development rate of eggs and their hatching time vary depending on the water temperature, which are faster at higher water temperatures.

The time described above is based on the water temperature of 22℃.

Not all fertilized eggs hatch out.

The hatching rate is calculated by counting the number of hatched larvae out of the fertilized eggs incubated under the same conditions.

Hatching rate (%) = number of larvae hatched / number of fertilized eggs x 100

Eggs are very fragile. They can be easily damaged or even die from the shock that occurs when transferred to a housing container.

Therefore, only the number of live fertilized eggs is used as the denominator for the calculation of the hatching rate.