Fig. 8. Light micrographs of the secondary lamellar structure of gills from (A) control or (B) Ni-exposed fish (394 µg Ni l^–1; 69 days). Note the thickened lamellae and decreased interlamellar water space in the treated gill (B). Sections are 1 µm thick, stained with Richardson's stain. Scale bars, 25 µm.