Composition and ultrastructure of elasmobranch granulocytes. I. Dogfishes (Squaliformes)

The blood granulocyte composition of 10 species of dogfish is given, together with ultrastructural observations made on Etmopterus baxteri Leydig organ and blood, and on spleens of Oxynotus bruniensis, Deania calcea, Scymnodon plunketi and blood of Centroscymnus crepidator . Neutrophilic granulocytes, which were common, had spherical granules that developed a dense core, which then lost contents to become lucent. Eosinophilic granulocytes had ovoid or elongated granules with a fibrillar content that became aligned longitudinally, and rarely formed an axial rod. Eosinophils had large spherical granules that were electron-dense but in early stages had a disorganised fibrillar content. These cells correspond to the neutrophils, heterophils and eosinophils, respectively, of other elasmobranchs.
Dogfish granulocytes are compared with those of other elasmobranchs, and their lack of similarity to those of higher vertebrates is noted.