Final answer:
Nucleated RBCs (nRBCs) are called metarubricytes, which is a stage in erythrocyte maturation when the cell still contains a nucleus before becoming a mature RBC.
Step-by-step explanation:
Nucleated RBCs (nRBCs) are referred to as metarubricytes. During the maturation of an erythrocyte, which starts in the red bone marrow, a stage is reached when the erythrocyte still contains a nucleus. This stage is known as the metarubricyte or normoblast stage.
The presence of nRBCs in the bloodstream is typically a sign of a pathological condition since mature human RBCs are anucleated and do not contain a nucleus under normal circumstances. Other terms listed such as schistocytes, eccentrocytes, and Heinz bodies all refer to different forms or conditions of erythrocytes but not to nucleated RBCs.