Composition and ultrastructure of elasmobranch granulocytes. II. Rays (Rajiformes)

Abstract

The blood granulocyte composition of seven species of ray is given together with ultrastructural observations made on the epigonal organ and blood of Puroraja spiniyera and the spleen of a deepwater rajid skate. Under the light microscope three granulocyte types, eosinophils, eosinophilic granulocytes and neutrophilic granulocytes could be distinguished. At the EM level two granulocyte types were apparent, one with elongated granules containing longitudinal fibrils that consolidated to form an axial rod-like inclusion, and the other with large, spherical, uniformly electron-dense granules. Correlation of light and electron microscope observations indicated that the neutrophilic granulocytes with weakly basophilic, elongated granules become weakly eosinophilic, as eosinophilic granulocytes, and these in turn develop to eosinophils with granules containing axial rods. The other granulocyte type forms another population of eosinophils with spherical granules.The inter-relationship of these granulocytes, the identification of eosinophilic granulocytes, or heterophils, as immature eosinophils, and the co-existence of two morphologically distinct eosinophil forms are discussed.

Composition and ultrastructure of holocephalan granulocytes

“…However, such simple lysosome-like granules are common in animal cells and are therefore of no phylogenetic significance. The smaller, lucent granules of Hydrolagus type I granulocytes are similar to spherical cells with lucent cores in Etmopterus baxteri, but no tubular elements were observed in the latter (Hine & Wain 1987a). The rod-like inclusions in Rhinochimaera granules are similar to those of type III granules of lamprey granulocytes (Page & Rowley 1983) and Catostomus commersonii neutrophils (Lester & Desser 1975), but were rarely observed and too poorly characterised to deduce strict homology.…”

“…but eosinophils of both species are negative for this enzyme (Hine & Wain 1988). It is therefore concluded that, like elasmobranchs (Hine & Wain 1987a, 1987b, 1987c many of the cells derive from the eosinophil lineage, but only the coarse granulocytes with their morphological, ultrastructural, and tinctorial similarities to eosinophils of higher vertebrates can be given a specific designation.…”

“…The coarse granulocytes (CG) of Harriotta, Hydrolagus, and Callorhynchus resemble the eosinophilic cells of lampreys (Rowley & Page 1985), Etmopterus spinax (Mattisson & Fange 1982), Scyliorhinus canicula type I granulocytes (Morrow & Pulsford 1980), coarse granulocytes in Etmopterus baxteri and Pavoraja spinifera (Hine & Wain 1987a, 1987b) five other elasmobranchs (Honma et al 1984), the Australian lungfish (Hine et al in press), and some (Bielek 1980) but not all (Weinreb 1963) teleosts, and are identified as eosinophils. Callorhynchus eosinophils differ from those of other fishes, except the lungfish (Hine et al in press) in the differentiation of an electron-dense core from a granular externum.…”

“…The range and intensity of leucocyte enzymes also increases from Rhinochimaera to Hydrolagus sp. (Hine & Wain 1988).…”

“…Most lymphocyte development occurs in the large thymus and spleen. This study examines granulocyte development in orbital tissue and blood of four holocephalans, Rhinochimaera pacifica, Harriotta raleighana, Hydrolagus sp., and Callorhynchus milii, and was carried out with a concurrent study on enzyme cytochemistry (Hine & Wain 1988 …”