Maybe somebody knows the answer to this. Why do some animals, like birds, have red blood cell that are nucleated, and others, like mammals, do not?
According to EB:
Although, IIRC, camels have nucleated RBCs…
quote:
mammalian red (blood) cells lack nuclei, an adaptation that makes them
even more efficient in oxygen transport.
I’m pretty sure birds blow away mammals when it comes to aerobic performance; the oxygen demands of flight must be quite enormous. Is this due to their “flow-thru” lung structure, or to nucleated RBCs? I’ve never heard anything regarding camels, but it would be interesting if true.
Dang i thought this was gonna be fun. I read nuCleated as nuDeated.Thought I’d found a new kink.
Another source implies the lack of a nucleus is need to keep the RBC flexible, so it can enter the capillaries.
Oh yeah, to nitpick: IIRC, the proper term for the un-nucleated variety is red blood corpuscle. The lack of a nuclei means it’s not technically a cell.
Another source implies the lack of a nucleus is need to keep the RBC flexible, so it can
enter the capillaries.
But if birds are more aerobically efficient (and I’ll take debate on this) --their nucleated RBCs are entering their capillaries just fine. My OP is WHY nucleated; I’m sorry if that wasn’t clear. I think I’ve heard reptiles (and maybe amphibians, I don’t know about them) also have nucleated RBCs. How come birds are so metabolically active/efficient and lizards not?
Because evolution is not an engineer.
Lizards have a low metabolism because that’s a good survival strategy – you hardly have to eat at all, so most of the time you can stay concealed.
Birds have a high metabolism because that’s a good survival strategy – you can outrun things you’re trying to eat, or that are trying to eat you.
Mammals have unnucleated RBC’s because the mutation occurred in an early mammal or proto-mammal, and it worked well.
Birds don’t because the mutation never happened in birds, or because the bone-marrow RBC-manufacturing process necessary for unnucleated RBC’s carried too much of a weight penalty.
John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams
Every time I think of something and return there is John K.already posted it. Birds are closer to reptiles than mamals are, and still have the ‘older’ ‘reptilian’ cells.