Some of the blood cells of non-mammalian vertebrates are very different from
mammalian cells in form but have comparable functions. The heterophil is the avian
equivalent of the neutrophil. Heterophils in birds have segmented nuclei that are partly
obscured by the large red-orange granules that pack the cytoplasm. Mature granules are
![]() Mature red cells in birds are large oval cells that contain oval nuclei. Immature red cells are rounder, have less oval to round nuclei, and polychromatophilic cytoplasm. Polychromatophilic red cells are fairly numerous in some avian species in the absence of anemia. The thrombocyte is the functional equivalent of the mammalian platelet. Thrombocytes in birds are small cells with round nucleus, very condensed chromatin, and small rim of gray cytoplasm. A few red granules are visible in some thrombocytes. Partial activation results in clumping of thrombocytes. Thrombocytes are distinguished from lymphocytes by their smaller size and gray, rather than blue, cytoplasm. Protozoan organisms of two genuses, Hemoproteus and Leukocytozoon, are commonly seen as parasites of avian blood cells. |