Avian Blood Cells
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 avian fusiform and many are slightly refractile. Immature heterophils have rounder granules and slightly blue cytoplasm. Avian eosinophils are slightly smaller than heterophils and their granules are round and a slightly different shade of orange. The granules of eosinophils in psittacine birds are light blue. Examples of these two types of avian eosinophils are shown here. The eosinophil on the left is from an African gray parrot and has large globular blue granules; the arrow points to the nucleus. Avian basophils contain many small purple granules, similar to basophils of some mammals. Avian lymphocytes and monocytes are similar to mammalian cells.

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.

Last Updated on Friday, March 22, 1996