Biological responses of the polychaete Hediste diversicolor (O.F.Müller, 1776) to inorganic mercury exposure: A multimarker approach Ginevra Moltedo * , Giacomo Martuccio, Barbara Catalano, Laura Gastaldi, Chiara Maggi, Claudia Virno-Lamberti, Anna Maria Cicero ISPRA Italian National Institute for Environmental Protection and Research, Via di Castel Romano 100, 00128 Rome, Italy highlights  H. diversicolor accumulates Hg in a dose-dependent manner, at least until 10 days.  Hg induces cellular damages in polychaetes, mainly at membrane level.  Hg not induces a significant DNA damage in polychaetes, at least at structural level.  The defence mechanism of H. diversicolor against Hg is strongly related to glutathione pattern. article info Article history: Received 9 July 2018 Received in revised form 7 December 2018 Accepted 8 December 2018 Available online 10 December 2018 Handling Editor: Jim Lazorchak Keywords: Biomarker Polychaete Mercury Toxicity abstract 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 mgL 1 ), bio- accumulation 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, Ca 2þ -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 suf- ficient to avoid neurotoxicity and some cellular damages, mainly at the intestinal level. © 2018 Published by Elsevier Ltd. 1. Introduction Mercury (Hg) is a priority hazardous substance (Reg. EC 2455/ 2001, ATSDR, 2015) that enters aquatic ecosystems through natural processes (e.g. geochemical emissions) and as a result of anthro- pogenic activities, such as fossil fuel combustions, mining and smelting operations, intense urbanization and chlor-alkali in- dustries (Cappello et al., 2016; Driscoll and McElroy, 2013; Ercal et al., 2001). As it is persistent in water and sediments, Hg is highly toxic to living organisms and tends to be bioaccumulated and biomagnified throughout food chains (Cappello et al., 2016). Given its potential effect on human health through fish consump- tion, the fate and bioaccumulation processes of Hg in marine en- vironments have received increasing attention worldwide (Minamata Convention on Mercury; Reg. EC 1881/2006). In general the toxicity of heavy metals depends on a wide spectrum of mechanisms and involves neurotoxicity, hepatotoxic- ity and nephrotoxicity (Stohs and Bagchi, 1995). The most impor- tant targets are proteins and enzymes, but they may interact with other biomolecules such as phospholipids and DNA (Juknys et al., 2009). Among heavy metals, Hg is considered to be one of the * Corresponding author. E-mail address: ginevra.moltedo@isprambiente.it (G. Moltedo). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere https://doi.org/10.1016/j.chemosphere.2018.12.064 0045-6535/© 2018 Published by Elsevier Ltd. Chemosphere 219 (2019) 989e996