Aquatic Toxicology 88 (2008) 207–213 Contents lists available at ScienceDirect Aquatic Toxicology journal homepage: www.elsevier.com/locate/aquatox Behavioral and biochemical responses of hybrid striped bass during and after fluoxetine exposure Kristen M. Gaworecki ∗ , Stephen J. Klaine Institute of Environmental Toxicology, Department of Biological Sciences, Clemson University, 509 Westinghouse Road, PO Box 709, Pendleton, SC 29670, United States article info Article history: Received 11 January 2008 Received in revised form 14 April 2008 Accepted 24 April 2008 Keywords: Behavioral assay Predator–prey Fluoxetine Serotonin abstract Environmental contaminants, including pharmaceuticals, can alter behavior and possibly impact popula- tion and community structures. One important behavior that could be impacted is the ability to capture prey. We hypothesized that sublethal fluoxetine exposure may lead to feeding behavior abnormalities in hybrid striped bass (Morone saxatilis × M. chrysops). Fluoxetine is an antidepressant that acts as a selective serotonin reuptake inhibitor (SSRI). A change in serotonin levels affects multiple behaviors including feed- ing, which is an important aspect in ecological fitness. This research characterized the impact of sublethal fluoxetine exposures on the ability of hybrid striped bass to capture fathead minnows (Pimephales prome- las). Bass were exposed to fluoxetine (0.0 g/l, 23.2 ± 6.6, 51.4 ± 10.9 and 100.9 ± 18.6 g/l,) for 6 days, followed by a 6-day recovery period in clean water. Brain serotonin activity and the ability of bass to cap- ture prey were measured every third day. Exposed fish exhibited a concentration- and duration-dependent decrease in ability to capture prey. Increased time to capture prey also correlated with decreases in brain serotonin activity. Serotonin activity also decreased in an exposure time- and concentration-dependent manner, maximally inhibited 23.7, 28.0, and 49.1% of control in the low, medium, and high treatments, respectively. Serotonin levels in exposed fish did not recover to control levels during the 6-day recovery period. These results suggest that sublethal exposure to fluoxetine decreases the ability of hybrid striped bass to capture prey and that serotonin can be used as a biomarker of exposure and effect. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Many pollutants adversely affect normal endocrine functions and unfortunately, these chemicals are ubiquitous in the environ- ment (Zala and Penn, 2004). The central nervous system is a target of endocrine-disruptors, so social behaviors under hormonal con- trol such as aggression, dominance, motivation, and activity are often directly impacted by exposure to these contaminants (Zala and Penn, 2004). Behavior is a major link between the organism and its environment (Little, 2002). It is both a result and determinant of molecular, physiological, and ecological aspects of toxicology; therefore it provides insight into various levels of biological orga- nization (Scott and Sloman, 2004). Behavioral responses also reflect an organism’s ecological fitness and their abilities to avoid preda- tors, select prey items, and reproduce (Little, 2002). Alterations in any of these behaviors, coupled with changes in physiology may alter population stability (Scott and Sloman, 2004). Fluoxetine (Prozac TM ) is an antidepressant that acts as a selec- tive serotonin reuptake inhibitor (SSRI). Serotonin functions as ∗ Corresponding author. Tel.: +1 864 646 2196; fax: +1 864 646 2277. E-mail address: kgawore@clemson.edu (K.M. Gaworecki). a neurotransmitter and hormone to regulate a wide range of behaviors including feeding activity, aggressive interactions, sex- ual behavior, and establishment of social hierarchies (Fent et al., 2006; Barton et al., 2002). SSRIs, like fluoxetine, act by inhibiting the reuptake of serotonin from the synaptic cleft, and increasing extracellular serotonin levels. They have been successful in improv- ing mood levels and decreasing appetite and aggression. Therefore, SSRIs are commonly prescribed for depression, compulsive behav- iors, and personality disorders (Brooks et al., 2003a). Fluoxetine, like most drugs, was developed with the intent of altering biochemistry and having specific pharmacological and physiological functions. Many drugs are polar, nonvolatile, and non- biodegradable (Bendz et al., 2005; Halling-Sørensen et al., 1998) so they tend to escape sedimentation and biological treatment in wastewater treatment plants (Bendz et al., 2005; Fent et al., 2006). They are persistent in order to reach the target site before becoming inactive, but this also increases the possibility of bioaccumula- tion in aquatic or terrestrial organisms (Halling-Sørensen et al., 1998). The high frequency of use and continual output of drugs from wastewater treatment plants and other sources simulates episodic or continuous exposures, rather than acute exposures. Consequently, low levels of fluoxetine (and other pharmaceuticals and personal-care products) have been found in treated sewage 0166-445X/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2008.04.011