Erythrocytes that are elliptical, not nucleated, and lack central pallor are most consistent with samples from which species?

• A. Llama
• B. Bird
• C. Horse
• D. Snake

Answer: (A)

Erythrocyte shape and nucleus presence vary by species, and these features are often key clues in identifying the source of a blood sample. In most mammals, red blood cells are non-nucleated discs with a distinct central pallor seen on a smear. Birds and reptiles have nucleated red blood cells, which means you wouldn’t expect to see the same central pallor pattern as in mammals, and their cells can be oval or elongated but still contain a nucleus. Camelids, such as llamas and alpacas, have a unique erythrocyte morphology: elliptical or cigar-shaped cells that are still anucleate, but notably lack the central pallor typical of other mammalian RBCs. Seeing elliptical, nucleus-free erythrocytes that do not show central pallor points to camelids, making llama the best match.