Ultrastructural study of chloride cells in the trunk epithelium of larval herring, Clupea harengus.
Mitochondria-rich cells of the mid-trunk region of herring larvae, as revealed by DASPMI staining under fluorescent microscopy, were identified as chloride cells. The chloride cells were generally solitary, and seldom made direct contact with each other. The shape of the cells varied with position on the body wall, those in dorsal locations being more compressed in the apical/basal direction. The structure of the chloride cells was similar to that described for other teleost species but there were considerable differences between ventral and dorsal cells. The volume fraction of mitochondria and diameters of mitochondria, cristae, and terminal expansions of cristae were all smaller in the dorsal cells. Tubular network density was relatively constant whilst smooth endoplasmic reticulum (SER) density and vesicotubular density, of the subapical cytoplasm, exhibited a high variation which did not correlate with the presence or absence of accessory cells. The apical membranes of both cell types were flush with the epithelium and did not form a crypt, even when interdigitating processes of an accessory cell were present. Accessory cell interdigitations were generally observed for the apical membrane of ventral cells but were seldom observed in the more dorsal cells of the segmental bands. The ultrastructural evidence suggests that the ventral cells are functional in ion pumping whereas the majority of chloride cells of the dorsal segmental bands were probably not functional in ion pumping.
Wales
B
B
Department of Biological and Molecular Sciences, University of Stirling, Stirling, Scotland. bill.wales@stir.ac.uk