Aquatic Toxicology 86 (2008) 142–147 The effect of starving and feeding on copper toxicity and uptake in Cu acclimated and non-acclimated carp Shodja Hashemi ∗ , Ronny Blust, Gudrun De Boeck Laboratory for Ecophysiology, Biochemistry and Toxicology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium Received 31 July 2007; received in revised form 16 October 2007; accepted 19 October 2007 Abstract Common carp (Cyprinus carpio) were fed two different food rations: 0.5% body weight (low ration, LR) and 5% body weight (high ration, HR) and were either acclimated to sublethal copper (1 M) for 28 days in softened Antwerp city tap water or not acclimated. Fish were exposed for 10 days to high Cu levels using four different concentrations (3.5, 6, 10, and 15 M) before and after the Cu acclimation. Fish tolerance against Cu exposure was evaluated, and gill, liver, and carcass Cu and sodium levels were measured in dead and surviving fish. HR fish were twice as sensitive as LR fish in both tests. The 96 h median lethal concentration (LC50) values for the non-acclimated LR and HR fish were 8.46 ± 2.79 and 4.34 ± 0.82 M, respectively. The fish became more resistant to low Cu concentrations after Cu acclimation and the LC50 values were slightly increased, reaching 9.20 ± 1.56 M and 5.01 ± 1.93 in LR and HR fish accordingly. Cu concentrations in the gills, liver, and carcass were significantly elevated in response to the short-term Cu exposure, and were significantly higher in LR fish than in HR fish. High Cu levels caused a net loss of sodium resulting in a severe ion regulatory disturbance. The rate of sodium loss increased linearly with increasing exposure concentrations. Cu acclimation resulted in reduced sodium loss and increased the resistance and tolerance to Cu toxicity. © 2007 Elsevier B.V. All rights reserved. Keywords: Acclimation; Accumulation; Common carp; Copper; Ionoregulation; Sodium 1. Introduction Copper is generally present in freshwater with a natural background from 0.20 to 30 g/L (Bowen, 1985). Although it is an essential element supporting physiological processes in fish, it may become inhibitory and ultimately toxic at higher concentrations (Furness and Rainbow, 1990). Copper levels between 4 and 160,000 g/L were considered toxic for carp depending on water quality and organism condition (Kaur and Dhawan, 1994; Deshmukh and Marathe, 1980; De Boeck et al., 2004). Some forms of copper are reactive and potentially haz- ardous (Sposito, 1986). Copper can accumulate in fish tissues (Yamamoto et al., 1997; De Boeck et al., 2003, 2004). Copper toxicity, accumulation, and excretion are species specific (Taylor et al., 2003; De Boeck et al., 2004) and even differ in different life stages (Kazlauskiene and Stasiunaite, 1999). Food quantity has recently been proposed to be considered among different exter- nal and internal factors that can affect copper bioavailability in ∗ Corresponding author. Tel.: +32 32653232; fax: +32 32653497. E-mail address: shodja.hashemi@student.ua.ac.be (S. Hashemi). carp (Hashemi et al., 2007a). A significant difference in cop- per accumulation in target organs between fed and starved carp during a sublethal waterborne copper exposure was reported (Hashemi et al., 2007a). Furthermore, substantial differences in metabolic rate, available energy, growth rate, and metabolic waste handling were established between fed and starved fish during sublethal waterborne copper exposure (Hashemi et al., 2007b). Therefore, differences in toxicity and copper uptake during acute waterborne copper exposure were likely to occur. In this study, the sensitivity of starved and fed fish against acute waterborne copper exposure was investigated. In addition, copper uptake, Na loss, and the effects of a long term acclima- tion to a sublethal Cu concentration (1 M) were studied. The relationships between copper accumulation and Na levels were determined, and Cu toxicity was examined. 2. Materials and methods 2.1. Animal holding—experimental set up Juvenile common carp, Cyprinus carpio, were obtained from the fish hatchery at the Wageningen University, The Nether- 0166-445X/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2007.10.008