Biochemical and histochemical aspects of lead exposure in dragonfly larvae (Odonata: Anisoptera)

The effects of lead exposure on the oxidative properties of different organs of dragonfly larvae (advanced instars) (Odonata: Anisoptera) were estimated by biochemical and histochemical methods. The lead load of the water was 20 μg/liter during 6 weeks at a temperature of 15°C and a normal diurnal rhythm. Lead was not accumulated in the brain, but in considerable amounts in the midgut, fat body, rectum, and cuticula of the test animals, while the control larvae showed astonishing concentrations of the heavy metal in the cuticula. The activities of the oxidative enzymes studied were significantly lowered only in the brain. Histochemically, lead could be visualized in all the organ tissues, apart from the brain, of the test animals, the controls exhibiting lead only in the cuticula. The enzyme histochemical evaluation of succinic dehydrogenase demonstrated typical changes of reaction intensities within the organs of the test animals, as compared to the controls. The results obtained are discussed in view of the specific biology of the tested animals and their normal biotope.