Ultrastructural morphology of the gill of the hybrid striped bass (Morone saxatilis x M-chrysops)

The fine structure of the principal cell types found in the gill filaments and secondary, respiratory lamellae of the hybrid striped bass (Morone saxatilis x M. chrysops) was studied by transmission electron microscopy. Most of the cell types generally resembled those observed at this level of resolution in other euryhyaline, teleostean species, and the mucus cells, epithelial cells, and cartilage cells were non-distinctive. Pillar cells were atypically flattened within the lamellae. The extensive cytoplasmic tubular system of the chloride cells was more densely distributed and was less branched than reported for many other teleosts. The vascular endothelial cells of the marginal, lamellar blood vessels were particularly striking because of their prominent, electron-dense cytoplasmic granules. Although the physiological function and chemical composition of these granules remain obscure, their presence suggests an important role of secretion into the vascular lumen. These gill data from normal specimens of this sport and commercial, hybrid species constitute a useful basis for interpreting gill changes in diseased striped bass.