The cell that does not contain a nucleus when it matures is called a red blood cell (also known as an erythrocyte).

Here's why:

* Function: Red blood cells are responsible for carrying oxygen throughout the body.

* Nucleus removal: During their development, red blood cells expel their nucleus and other organelles to maximize space for hemoglobin, the protein that binds oxygen.

* Benefits of no nucleus: This lack of a nucleus makes red blood cells more flexible and allows them to squeeze through tiny capillaries, delivering oxygen efficiently.

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