Structural and circulatory changes in the secondary lamellae of salmo gairdneri gills after sublethal exposures to dehydroabietic Acid and Zinc

Rainbow trouts (Salmo gairdneri Richardson) were exposed to sublethal concentrations of dehydroabietic acid (DHAA) (1.55 mg.1−1) or zinc (1.25 mg. I−1) in a semistatic system for 96 h. Different secondary lamellar structures were analysed morphometrically from oriented 1 μm sections. DHAA induced hypertrophy of the epithelium. The number of chloride cells was higher than in control gills. Zinc induced detachment of the epithelium from the underlying pillar cell system. The fusion of secondary lamellae reduced the surface area of the epithelium. Both substances induced a marked vasoconstriction in the secondary lamellar capillaries. The haematocrit value of the secondary lamellar blood was higher in both the exposed groups than in the control group.