Morphology and cytochemistry of leucocytes and thrombocytes of six species of fish

Cytochemical reactions of blood leucocytes and thrombocytes from six species of fish, rainbow trout (Onchorhynchus mykiss), coho salmon (Onchorhynchus kisutch), white sturgeon (Acipenser transmontanus), goldfish (Carassius auratus), striped bass (Morone saxatulis), and channel catfish (Ictalurus punctatus) were determined. Because the staining reactions were generally similar to the reactions found in mammalian leucocytes with similar morphological features, it is reasonable to classify fish leucocytes using the same terminology as is used for mammalian leucocytes. However, in some species leucocytes with features similar to mammalian eosinophils or basophils were not found. In goldfish leucocytes were found that had segmented nuclei and unstained, moderately refractile cytoplasmic granules. These cells were classified as segmented, granular leucocytes. Although these cells do not appear similar to any mammalian or avian leucocyte, the pattern of positive cytoplasmic alkaline phosphatase staining and negative granular staining is similar to that of equine eosinophils.