Biological responses of the polychaete Hediste diversicolor (O.F.Müller, 1776) to inorganic mercury exposure: A multimarker approach.

Mercury (Hg) is a global priority pollutant given its relevance in terms of environmental damage and threat to human health. Its ecotoxicity was tested using the benthic keystone species Hediste diversicolor as target species. After 10 days of exposure to different levels of inorganic Hg (10 and 50 µg L-1), bioaccumulation and a wide range of biological responses were evaluated at different biological levels, including biomarkers of exposure, neurotoxicity, oxidative stress, genotoxicity and cytochemistry. In controlled laboratory conditions, Hg was taken up by H. diversicolor in a dose-response manner and caused a range of biological responses, including oxidative stress (GSTs, GPx, GSH-2GSSG, and TOSCA), neurotoxicity (AChE), and cellular damages at the membrane level (LFs, NLs, Ca2+-ATPase); however, it did not cause significant DNA damage or mortality. This study confirms the capability of H. diversicolor to tolerate high levels of metals and clarifies the mechanisms underlying the damage caused by waterborne Hg and the defense mechanisms, activated in this species. In particular, detoxification of the inorganic form of Hg in this species was found to be strongly related to glutathione expression and several antioxidant enzymes of the antioxidant system. This process also efficiently minimized negative effects on DNA and prevented death, but was not sufficient to avoid neurotoxicity and some cellular damages, mainly at the intestinal level.