What is the purpose of the nuclei in blood cells?

Question

I was reading about the similarities between birds and reptiles, and one thing they have in common is blood cell structure. Their white AND red blood cells have a nucleus, but humans only have nuclei in WHITE blood cells. I understand that the lack of nuclei in human red blood cells allows for more room to carry oxygen. So what is the purpose of having nuclei in red blood cells for reptiles and birds?

Tss · Accepted Answer

Red blood cells (RBC) or erythrocytes are continually formed in the bone marrow. RBC originate from nucleated stem cells, which mature into nucleated erythroblasts, then differentiate into a-nuclear reticulocytes and finally into RBC. RBC are terminally differentiated cells (they cannot divide anymore) and are shed from the bone marrow into the blood circulation. They live approximately 120-180 days. 

In contrast to mammals, RBCs in birds, reptiles and other "lower" vertebrates have a nucleus. The a-nucleated erythrocyte, as it is seen in mammals, is considered more evolutionarily "advanced". 
The lower vertebrates (e.g., birds) are considered earlier on the evolution ladder and have a different circulatory system .
In addition to the differences in the circulatory system, mammals have smaller end-bloodvessels (capillaries of about 3 micron in diameter) than birds. In order to squeeze through these small blood capillaries, RBC which are about 10 micron in diameter, must be very flexible. The presence of a nucleus would prevent big nucleated RBC to squeeze through these small capillaries. Therefore, during the evolutionary development, nature has found that it was better to get rid of the nucleus and also other cell organelles (e.g., endoplasmic reticulum for protein synthesis) which were not needed for their actual function as oxygen carrier. 

As homeotherms evolved, they had increased oxygen demands due to different metabolic requirements. Birds appear to have adapted to increased oxygen demands by developing a "flow-through" respiratory system (interconnecting tubes for continuous flow, rather than blind-ended alveoli) that's more efficient than mammals'. Mammals may have diverged here and developed anucleated RBC's with increased oxygen carrying capacity to adapt to the increased oxygen demands. 

Best Regards
TSS

? · Answer

the nucleus is had to direct the cellular equipment to make the mandatory proteins and enzymes . in case of rbc , that's in charge for production of haemoglobin and carbonic anyhdrase the two considered one of that are enclosed interior the rbc. later to advance packing section for hb molecules and additionally to advance floor section for absorption of oxygen,carbon dioxide , that's bumped off

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What is the purpose of the nuclei in blood cells?

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