The sensitivity of two biochemical biomarkers in terrestrial isopods after short-term copper exposure
Biochemical biomarkers, e.g. enzyme activities, have been traditionally considered a very sensitive and specific tool to characterize the hazard of pollutants to organisms. Among them, considerable attention was given to antioxidant enzymes catalase and glutathione S-transferase, which respond to changes in the quantity of reactive oxygen species. In the present study, the two enzymes were assessed in terrestrial isopods Porcellio scaber acutely (3 days) exposed to redox active copper and compared to their whole-organism responses, such as feeding, weight change and survival. The animals were fed with copper contaminated food for 3 days and afterwards for another 3 and 6 days with uncontaminated food. In contrast to expectations, no changes of antioxidant enzymes were found throughout the experiment, while feeding parameters were already decreased after 3 days of exposure at the highest exposure concentration 5000 μg/g dry food. The concentrations tested were not acutely lethal for isopods and did not affect their weight change. These findings imply that biochemical biomarkers in some cases are not a fast and sensitive measure to characterise the hazard of chemicals. The observed finding is probably the result of interplay between a very short time of exposure and the type of chemical chosen. Namely, a special relationship exists between isopods and copper, since it is an essential element for P. scaber.
It is recommended that more data on the relationship between lower and higher-level biomarkers in isopods after different exposure periods is needed and this knowledge will increase their relevance in future studies on the hazard of new emerging contaminants.