Fig. 8. Apical surfaces of the chloride cells of young adult Geotria australis in freshwater (A) and after migration to seawater (B). Lateral views of the filament, showing at the bottom its base, where lamellae are absent. The chloride cells form rows (arrows) at the base of the filament, which continue into the interlamellar region. Note the changes of the apical surface of the chloride cell from a small circular region enlarged by microvilli in freshwater (A) to a comparably large rectangular region lacking microvilli in seawater (B). Intercalated MR cells are encircled in A and absent in B. L, lamellae. Scale bars, 30 µm (A,B). Reprinted from Bartels et al. (1996) with kind permission from the publishers.