The effects of social isolation on steroid hormone levels are modulated by previous social status and context in a cichlid fish L. Galhardo, R.F. Oliveira ⁎ Unidade de Investigação em Eco-Etologia, Instituto Superior de Psicologia Aplicada, Rua Jardim do Tabaco, 34, 1149-041 Lisboa, Portugal Champalimaud Neuroscience Programme, Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, 2780-156 Oeiras, Portugal abstract article info Article history: Received 28 May 2013 Revised 16 October 2013 Accepted 21 October 2013 Available online 27 October 2013 Keywords: Cortisol 11-Ketotestosterone Testosterone Androgen Cognitive appraisal Tilapia Social isolation is a major stressor which impacts the physiology, behaviour and health of individuals in gregarious species. However, depending on conditional and contextual factors, such as social status and group composition, social isolation may be perceived differently by different individuals or even by the same individuals at different times. Here we tested the effects of social status (territorial vs. non-territorial) and previous group composition (i.e. type of social group: mixed sex group with two territorial males, TT vs. mixed sex group with one territorial and one non-territorial male, TnT) on the hormonal response (androgens and cortisol) to social isolation in a cichlid fish (Oreochromis mossambicus). The different steroid hormones measured responded differ- entially to social isolation, and their response was modulated by social factors. Social isolation elicited a decrease of 11-keto formation only in territorial males, whereas non-territorial males present a non-significant trend for increasing KT levels. Testosterone did not respond to social isolation. Cortisol only increased in isolated individ- uals from TnT groups irrespective of social status (i.e. both in territorials and non-territorials). These results sug- gest that it is the perception of social isolation and not the objective structure of the situation that triggers the hormonal response to isolation. © 2013 Elsevier Inc. All rights reserved. Introduction The social environment plays a key role in the life of group-living species, having a major impact on many biological processes including brain and behaviour (Fernald, 2012; Fernald and Maruska, 2012). Individuals from social species are motivated to establish and maintain social connections, showing a preference for being in the presence of conspecifics and valuing them as social rewards (e.g. fish: Al-Imari and Gerlai, 2008; mammals: Thiel et al., 2008). On the other hand, in social species deprivation from social conspecifics (i.e. social isolation) is a major stressor, which impacts the physiology, behaviour and health of individuals (Cacioppo et al., 2011; Hennessy, 1997). Detrimental effects of social isolation seem to be universal across different animal taxa, as they have been documented from fruit flies, in which social isolation decreases lifespan (Ruan and Wu, 2008), to mammals (e.g. mice, rat, rabbit, and humans), in which it is associated with increased hy- pothalamic–pituitary–adrenal (HPA) axis activation, increased sympa- thetic activity, increased oxidative stress, immunosuppression, lack of inflammatory control, and sleep disturbances (for a brief review see Cacioppo et al., 2011). Interestingly, in humans these detrimental effects are not only associated with real social isolation but are also triggered simply by the perception of social isolation (i.e. loneliness), and together contribute to higher rates of morbidity and mortality in older adults (Cacioppo et al., 2011). In fish, social isolation has been shown to impact locomotion, exploratory behaviour, feeding, aggressive behaviour and androgen and corticosteroid levels (Gómez-Laplaza and Morgan, 2000, 2003; Hannes and Franck, 1983). Despite these well known detrimental effects of social isolation, in animal experimentation individuals are commonly removed from their social groups and tested individually in standard experimental situations. Social isolation is also commonly used in behavioural endocrinological studies as a way to standardize the initial conditions (i.e. baseline hormone levels and previous social experience) in which animals enter an experiment (e.g. Galhardo et al., 2008; Oliveira et al., 1996, 2005). However, individual differences in the perception of social isolation are present in humans and modulate the above-mentioned impact of social isolation on biological function (e.g. Cacioppo et al., 2009; Cole et al., 2007). In recent years the concept that cognitive appraisal is involved in the processing of social information has been extended to animals (Mendl et al., 2010; Paul et al., 2005). Cognitive ap- praisal theory has been developed in emotion research and proposes that a response to an emotion-eliciting stimulus is not just a result of di- rect effects of perceptual information, but rather a function of what that perceptual information means to the organism at that particular time. Therefore, emotional experiences depend on some kind of general appraisal mechanism that allows organisms to evaluate the stimulus, that is its valence and salience, and to determine the appropriate Hormones and Behavior 65 (2014) 1–5 ⁎ Corresponding author at: Unidade de Investigação em Eco-Etologia, Instituto Superior de Psicologia Aplicada, Rua Jardim do Tabaco, 34, 1149-041 Lisboa, Portugal. Fax: +351 218860954. E-mail address: ruiol@ispa.pt (R.F. Oliveira). 0018-506X/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.yhbeh.2013.10.010 Contents lists available at ScienceDirect Hormones and Behavior journal homepage: www.elsevier.com/locate/yhbeh