Field studies on the relation between the accumulation of heavy metals and metabolic and HSR in the bearded horse mussel Modiolus barbatus Maria Katsikatsou a , Andreas Anestis a , Hans O. Pörtner b , Thodoros Kampouris c , Basile Michaelidis a, ⁎ a Laboratory of Animal Physiology, Department of Zoology, School of Biology, Faculty of Science, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece b Alfred-Wegener-Institut für Polar-und Meeresforschung, Ökophysiologie mariner Tiere, Postfach 120161, D-27515 Bremerhaven, Germany c Department of Marine Science, School of The Environment, University of The Aegean, University Hill 81100 Mytilene, Greece abstract article info Article history: Received 1 June 2010 Received in revised form 5 October 2010 Accepted 5 October 2010 Available online 16 October 2010 Keywords: Bivalves Heavy metals Cd and Pb Hsps Metabolism The present study aims to examine whether the seasonal changes in the levels of heavy metals Cd and Pb in the gills of sublittoral mussel Modiolus barbatus from populations distributed in Thermaikos Gulf are correlated to seasonal molecular (Heat Shock Response) and metabolic stress responses of this species. Our results indicate a season effect in the accumulation of heavy metals in the gills of bivalves in the area of Thermaikos Gulf, possibly implicating biological (reproductive cycle), natural (rivers' flow) and anthropogenic factors. Among the members of heat shock proteins (Hsps) examined, inducible Hsp70 seemed to play a major cytoprotective role against toxicity of metals. However, bivalves' tolerance against heavy metals may decrease during warming, arising further questions for their survival in context of global warming. © 2010 Elsevier Inc. All rights reserved. 1. Introduction Pollution of aquatic environments by trace metals is a world-wide problem due to the persistency and continuing accumulation of metals in the environment (Group of experts on the scientific aspects of marine environmental protection, GESAMP, 1987; de Mora et al., 2004; Hyun et al., 2006). The distribution of heavy metals within the aquatic environments is governed by a complex of anthropogenic and natural processes including river or atmospheric inputs, coastal and seafloor erosion, biological activities, water drainage, discharge of urban and industrial wastewaters (Leivouri, 1998; Ip Carman et al., 2007). Cadmium (Cd) which is one of the most toxic metals found in coastal zones and estuaries where it is predominantly released by human activities such as smelting, mining, battery manufacturing, and pigment and plastic production (Group of experts on the scientific aspects of marine environmental protection, GESAMP, 1987; Pinot et al., 2000). Stress proteins such as heat shock proteins (Hsps) and metallothioneins (MTs) play a key role in cellular protection against environmental stress caused by the accumulation of heavy metals (Fabbri et al., 2008; Franzellitti et al., 2010). In ectotherms (that constitute N 99% of species in aquatic realms), susceptibility to metal pollutants can be strongly modified by the environmental temperature due to its direct effects on all biochemical and physiological reactions (Hochachka and Somero, 2002; Sokolova and Lannig, 2008). Earlier studies have shown that moderately elevated temperatures exaggerate toxic effects of Cd on aquatic ectotherms through increased mitochondrial damage and oxidative stress, elevated energy demand, impaired ventilatory and/or circulatory capacities and resulting energy deficiency (Sokolova and Lannig, 2008). The elevated ambient temperatures can increase the sensitivity of marine ectotherms to toxic metals resulting in a reduced aerobic scope due to mitochondrial dysfunction and elevated energy demand for basal maintenance, deterioration in physiological condition and oxidative stress (Sokolova, 2004; Cherkasov et al., 2006; Lannig et al., 2006; Ivanina et al., 2010a,b). According to the hierarchical model of the mechanisms of thermal tolerance in aquatic ectotherms, survival under the conditions of acute heat stress is critically dependent on the molecular protective mechan- isms maintaining cellular integrity such as the expression of heat shock proteins (Hsps). Alterations of the capacity of these cytoprotective systems can have serious implications for the whole-organism survival under the extreme temperature conditions (Pörtner, 2002; Pörtner and Knust, 2007; Pörtner and Farrell, 2008). However, interactive effects of temperature and pollutants on ectotherm physiology are not well understood. In particular, little is known about the combined effects of temperature and pollution stress on immune function and haemolymph Comparative Biochemistry and Physiology, Part C 153 (2011) 133–140 ⁎ Corresponding author. Tel.: + 30 2310 998401; fax: + 30 2310 998269. E-mail address: michaeli@bio.auth.gr (B. Michaelidis). 1532-0456/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.cbpc.2010.10.001 Contents lists available at ScienceDirect Comparative Biochemistry and Physiology, Part C journal homepage: www.elsevier.com/locate/cbpc