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.

youdao

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.

youdao

One of the most obvious things about a red blood cell is it doesn't have nucleus, it has no nucleus.

红细胞最为明显的不同就是,它是无核的,它没有细胞核

耶鲁公开课 - 生物医学工程探索课程节选