Mercury(II) bioaccumulation and antioxidant physiology in four aquatic insects.

We examined Hg(II) bioaccumulation and compartmentalization patterns in conjunction with antioxidant responses in four aquatic insect species: two caddisflies (Chimarra sp. and Hydropsyche betteni) and two mayflies (Maccaffertium modestum and Isonychia sp). Total antioxidant capabilities differed among unexposed larvae, with both caddisfly species exhibiting elevated antioxidant activities relative to the mayflies. We were able to account for these differences by examining the constitutive activities of catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), and superoxide dismutase (SOD), in the four species. We also examined levels of reduced and oxidized glutathione and cysteine in the insects. Glutathione peroxidase and SOD were the most responsive to Hg exposure, with GPx catalytic activity increasing between 50 and 310%. Superoxide dismutase activity decreased between 35 and 50%. This SOD suppression was shown to be dose-dependent in both caddisflies, butthe strength of this suppression did not appear to be related to rates of uptake. Surprisingly, little Hg (<10%) was found in the heat-stable cytosolic protein subcellular compartment in each of the four species, suggesting that Hg was not well detoxified. By combining bioaccumulation studies with other physiological measures, we can begin to better understand the consequences of trace metal pollutants in nature.

Changes in the timing of reproduction following chronic exposure to ibuprofen in Japanese medaka, Oryzias latipes.

Effluents from wastewater treatment plants and untreated sewage constitute a low concentration but continuous source of pharmaceutical products to the aquatic environment. One such drug, ibuprofen, is a non-steroidal anti-inflammatory agent that primarily acts through inhibition of cyclooxygenase (COX) activity. Oryzias latipes (Japanese medaka) were exposed for 6 weeks via water to three concentrations of ibuprofen (1-100 microg/L nominal concentrations) and a water control. Reproductive parameters, including frequency of spawning, fecundity, egg size, and rate of fertilization, were measured for each pair of adult medaka following 6 weeks of exposure. Livers homogenates from exposed individuals were assayed for COX activity and whole individuals were histologically examined for tissue damage. Increasing exposure to ibuprofen significantly increased the number of eggs per reproductive event, but decreased the number of spawning events per week. Liver tissue collected from females had less variability in COX activity with increasing concentration of ibuprofen exposure, and tended to have elevated hepatosomatic indices. No pathological damage was evident the in the gills, livers and head kidneys of animals from the highest exposure group. The results of this experiment begin to show that exposure to chronic low levels of ibuprofen alter the pattern of reproduction and may produce sex-specific responses in teleosts.