Aquatic Toxicology 142–143 (2013) 123–137 Contents lists available at ScienceDirect Aquatic Toxicology jou rn al hom ep age: www.elsevier.com/locate/aquatox Compensatory responses in common carp (Cyprinus carpio) under ammonia exposure: Additional effects of feeding and exercise Marjan Diricx a,1 , Amit Kumar Sinha a,∗,1 , Hon Jung Liew a,b , Nathalie Mauro a , Ronny Blust a , Gudrun De Boeck a a Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium b Institute of Tropical Aquaculture, University Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia a r t i c l e i n f o Article history: Received 4 July 2013 Received in revised form 8 August 2013 Accepted 13 August 2013 Keywords: Ammonia toxicity Common carp Fasting Swimming Energy metabolism Ionoregulation a b s t r a c t Ammonia is an environmental pollutant that is toxic to all aquatic animals. The toxic effects of ammo- nia can be modulated by other physiological processes such as feeding and swimming. In this study, we wanted to examine these modulating effects in common carp (Cyprinus carpio). Fish were either fed (2% body weight) or starved (unfed for seven days prior to the sampling), and swimming at a sus- tainable, routine swimming speed or swum to exhaustion, while being exposed chronically (up to 28 days) to high environmental ammonia (HEA, 1 mg/L ∼ 58.8 mol/L as NH 4 Cl at pH 7.9). Swimming per- formance (critical swimming speed, U crit ) and metabolic responses such as oxygen consumption rate (MO 2 ), ammonia excretion rate (J amm ), ammonia quotient, liver and muscle energy budget (glycogen, lipid and protein), plasma ammonia and lactate, as well as plasma ion concentrations (Na + , Cl - , K + and Ca 2+ ) were investigated in order to understand metabolic and iono-regulatory consequences of the exper- imental conditions. Cortisol plays an important role in stress and in both the regulation of energy and the ion homeostasis; therefore plasma cortisol was measured. Results show that during HEA, J amm was elevated to a larger extent in fed fish and they were able to excrete much more efficiently than the starved fish. Consequently, the build-up of ammonia in plasma of HEA exposed fed fish was much slower. MO 2 increased considerably in fed fish after exposure to HEA and was further intensified during exercise. Dur- ing exposure to HEA, the level of cortisol in plasma augmented in both the feeding regimes, but the effect of HEA was more pronounced in starved fish. Energy stores dropped for both fed and the starved fish with the progression of the exposure period and further declined when swimming to exhaustion. Overall, fed fish were less affected by HEA than starved fish, and although exercise exacerbated the toxic effect in both feeding treatments, this was more pronounced in starved fish. This suggests that fish become more vulnerable to external ammonia during exercise, and feeding protects the fish against the adverse effects of high ammonia and exercise. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The increase in the level of water borne ammonia in natural waters and in culture systems is a serious health issue for aquatic animals (Dosdat et al., 2003; Foss et al., 2004; Lemarie et al., 2004; Abbreviations: HEA, high environmental ammonia; AQ, ammonia quotient; RS, routine swimming; ES, exhaustive swimming; RSAF, routine swum ammonia exposed fed; RSAS, routine swum ammonia exposed starved; ESAF, exhaustive swum ammonia exposed fed; ESAS, exhaustive swum ammonia exposed starved; MO2, oxygen consumption rates; Jamm, ammonia excretion rate; Tamm, total ammo- nia; U crit , critical swimming speed. ∗ Corresponding author. Tel.: +32 32 653 779; fax: +32 32 653 497. E-mail addresses: sinha cife@rediffmail.com, sinha cife@yahoo.co.in (A.K. Sinha). 1 These authors contributed equally to the work. Person-Le Ruyet et al., 1997). In general, ammonia is produced as a metabolic waste product of protein catabolism and/or gener- ated from decomposition of organic material, industrial emission or produced by micro-organisms. High environmental ammonia (HEA) not only hinders ammonia excretion in fish but can also cause net uptake of ammonia from the environment. Hence, dur- ing HEA fish are confronted simultaneously with accumulation of endogenous ammonia and uptake of exogenous ammonia, caus- ing adverse effects on the performance and welfare (Eddy, 2005; Randall and Tsui, 2002). Waterborne ammonia can exist in two forms, the unionized ammonia (NH 3 ) and the ionized form (NH 4 + ) (McKenzie et al., 2003; Randall and Tsui, 2002), and the sum of NH 3 and NH 4 + comprises the total ammonia concentration. Throughout this paper, the term ‘ammonia’ is used to refer to total NH 3 + NH 4 + , whereas these chemical symbols refer to the individual compo- nents of ammonia gas (NH 3 ) and ammonium ion (NH 4 + ). Since 0166-445X/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aquatox.2013.08.007