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How do oligolecithal, telolecithal, and megalecithal eggs differ in yolk distribution?
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Animal development
The embryos of many animals appear similar to one another in the earliest stages of development and progress into their specialized forms in later stages.
Eggs are classified based on the quantity and distribution of yolk, which serves as the nutritive material for a developing embryo. These classifications differ as follows:
- Oligolecithal eggs: These contain a small quantity of yolk that is evenly distributed throughout the egg.1
- Telolecithal eggs: These possess a larger amount of yolk that is unevenly distributed, being concentrated toward the vegetal pole of the egg.21
- Megalecithal eggs: These contain even greater amounts of yolk compared to the other types, stored either in granules or as a compact mass.1
The distribution of yolk is closely related to the polarity of the egg, which features an active animal pole containing the nucleus and a less active vegetal pole where most of the yolk is typically stored.1