哺乳动物中的红细胞成熟时是无核的，这意味着它们缺乏细胞核。
Erythrocytes in mammals are anucleate when mature, meaning that they lack a cell nucleus.
其他的脊椎动物，比如说鱼类，爬行动物和鸟类等红细胞有核的动物的红细胞却没有进化成无核的红细胞。
Other vertebrates such as fish, reptiles and birds have red cells that contain nuclei that are inactive.
其他的脊椎动物，比如说鱼类，爬行动物和鸟类等红细胞有核的动物的红细胞却没有进化成无核的红细胞。
Other vertebrates such as fish, reptiles and birds have red cells that contain nuclei that are inactive.
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