Neuromodulation of the agonistic behavior in two species of weakly electric fish that display different types of aggression

Abstract

SummaryAgonistic behavior has shaped sociality across evolution. Though extremely diverse in types of displays and timing, agonistic encounters always follow the same conserved phases (evaluation, contest and post-resolution) and depend on homologous neural circuits modulated by the same neuroendocrine mediators across vertebrates. Among neuromodulators, serotonin (5-HT) is the main inhibitor of aggression, and arginine vasotocin (AVT) underlies sexual, individual and social context differences in behavior across vertebrate taxa. We aim to demonstrate that a distinct spatio-temporal pattern of activation of the social behavior network characterizes each type of aggression by exploring its modulation by both the 5-HT and AVT systems. We analyze the neuromodulation of aggression between the intermale reproduction-related aggression displayed by the gregarious Brachyhypopomus gauderio and the non-breeding intrasexual and intersexual territorial aggression displayed by the solitary Gymnotus omarorum. Differences in the telencephalic activity of 5-HT between species were paralleled by a differential serotonergic modulation through 1A receptors that inhibited aggression in the territorial aggression of G. omarorum but not in the reproduction-related aggression of B. gauderio. AVT injection increased the motivation towards aggression in the territorial aggression of G. omarorum but not in the reproduction-related aggression of B. gauderio, whereas the electric submission and dominance observed in G. omarorum and B. gauderio, respectively, were both AVT-dependent in a distinctive way. The advantages of our model species allowed us to identify precise target areas and mechanisms of the neuromodulation of two types of aggression that may represent more general and conserved strategies of the control of social behavior among vertebrates.

Social status differences regulate the serotonergic system of a cichlid fish, Astatotilapia burtoni

“…Manipulation of AVT levels in fish can affect courtship behaviors and induce social avoidance (Salek et al, 2002;Silva et al, 2013;Thompson and Walton, 2004). In the golden hamster, AVP facilitated offensive aggression in males, which can be blocked by pretreatment with a selective serotonin re-uptake inhibitor (SSRI) (Delville et al, 1996;Ferris and Delville, 1994) or 5-HTR 1A agonist (Ferris et al, 1999).…”

Melatonin Regulates Daily Variations in Electric Behavior Arousal in Two Species of Weakly Electric Fish with Different Social Structures

“…Interestingly, these differences resemble the species differences in the dynamics of the nocturnal increase presented in this study. In addition, AVT has a demonstrated role in establishing the dominant-subordinate status in both species [Perrone, 2012;Silva et al, 2013] and in the social component of the nocturnal increase of EOD-BR in B. gauderio [Perrone et al, 2010]. Taking all these observations into account, it is reasonable to expect that AVT mediates the interspecific differences in amplitude and timing of the nocturnal increase in EOD-BR.…”

Behavioral ecology, endocrinology and signal reliability of electric communication

“…Brachyhypopomus gauderio enhances its EOD following a circadian rhythm: reducing rate, amplitude and duration of the EOD during the day and increasing them during nighttime activity (Silva et al, 2013;Franchina et al, 2001;Franchina and Stoddard, 1998;Silva et al, 2007;Stoddard et al, 2007). Both males and females follow this circadian pattern, but it is accentuated in males (Stoddard et al, 2007).…”