A series of studies were conducted to investigate the link between chronic exposure to a suite of heavy metals and sub-lethal responses in the ground beetle, Pterostichus oblongopunctatus (Coleoptera: Carabidae). Five sites in Southern Poland were sampled along a gradient of cadmium, lead, zinc and copper pollution. Body burdens of metals ranged from 79 to 201 ug/g Zn, 0.74 to 8.66 ug/g Pb and 1.14 to 10.8 ug/g Cd. The first experiments detected a differential survival in beetles along the gradient after exposure to the insecticide, dimethoate, and during a food deprivation study. Beetles from the most polluted site had a median survival of 12 hours after exposure to 0.1 ug a.i. of dimethoate versus 359 hours in the reference site. Additional studies investigated a physiological mechanism for differential survival. Two detoxification enzymes, glutathione S-transferase and carboxylesterase, were measured to determine trends in kinetic activity along the gradient. Signficantly elevated levels of glutathione S-transferase were detected in females from the two most polluted sites compared with the reference site. However, no significant differences were detected among male carabids, suggesting the importance of gender in environmental assays. Similarly, significance was observed for carboxylesterase activity in females at the polluted sites, but not in males. The final series of experiments examined the role respiration rates as a biomarker of metal exposure. Resting respiration rates were determined prior to and after dosing with dimethoate to determine the ability of P. oblongopunctatus to respond to acute stress. Beetles from the reference and polluted sites did not vary in their ability to induce respiration rates after exposure to the insecticide, suggesting limited utility of this biomarker as an indicator of metal exposure in carabids.
Species 1: Coleoptera Carabidae Pterostichus oblongopunctatus (ground beetles)
Keywords: ecotoxicology, biomarkers
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