Aggression Levels Affect Social Interaction in the Non‐Breeding Territorial Aggression of the Weakly Electric Fish, Gymnotus omarorum

Abstract

Animals typically decide whether to fight or retreat from conspecifics based on their individual estimates of the costs and benefits of fighting. Theoretical models predict how contenders solve a conflict, but the evaluation processes involved in these decisions depend on multiple factors that are difficult to explore experimentally. We addressed these questions using the non-breeding territorial aggression of Gymnotus omarorum, in which subordinates make three distinctive decisions to signal their submission during a fight: (1) interruption of their electric discharges to hide from the dominant, (2) stop attacking and retreat, and (3) emission of 'chirps', transient submissive electric signals. We confirmed that subordinates take into account the aggressive performance of dominants to shape their own agonistic decisions and performance. The intensity of aggression is highly correlated with an agonistic dyad, and the decision of subordinates to retreat is influenced by the attack rates of dominants. When we lowered the aggression of expected dominants with a 5-HT 1A receptor agonist, the correlation between the two contenders' aggression levels was lost and subordinates completely stopped emitting electric chirp signals. The aforementioned results contribute to the understanding of the decision-making strategies driven by social challenge inherent to agonistic encounters.

Extra-gonadal steroids modulate non-breeding territorial aggression in weakly electric fish

“…Territorial aggression of G. omarorum in intra-and intersexual interactions during the non-breeding season has been described previously (Batista et al, 2012;Silva et al, 2013;Zubizarreta et al, 2012Zubizarreta et al, , 2015. Accordingly, in this study, surgically-identified males displayed typical agonistic behavior in dyadic interactions (Fig.…”

“…The electric signals depend on a very well-known and tractable neural circuit (Caputi et al, 2005;Stoddard, 2002), and the relative simplicity of this electromotor circuit offers important operational advantages for studying the neuroendocrine control of behavior. The non-breeding territorial aggression of G. omarorum constitutes a clear example of non-sex biased territorial aggression, unique among teleosts, in which we can precisely identify the phases of the agonistic encounter, the emergence of the dominance-subordination status, levels of aggression and an orderly sequence of submissive electric displays (Batista et al, 2012;Silva et al, 2013;Zubizarreta et al, 2012Zubizarreta et al, , 2015. The original description of the non-breeding agonistic behavior of G. omarorum showed that size asymmetry (but not individual sex nor dyad composition) predicted contest outcome (Batista et al, 2012).…”

“…The weakly electric fish Gymnotus omarorum, a well-established neuroethological model (reviewed in Caputi et al, 2005;Lorenzo et al, 2006;Silva et al, 2002), shows inter-and intrasexual nonbreeding territorial aggression (Batista et al, 2012;Zubizarreta et al, 2012Zubizarreta et al, , 2015 modulated by neuropeptides (Silva et al, 2013) and social context and monoamines (Zubizarreta et al, , 2015. The electric organ discharge (EOD) plays a key role in communication, signaling submission during aggressive encounters and subordinate status once rank is determined (Batista et al, 2012;Silva et al, 2013).…”

Automated pulse discrimination of two freely-swimming weakly electric fish and analysis of their electrical behavior during dominance contest

“…The dominant fish actively swims and explores the whole environment, while the submissive fish often remains still. Sequences of Inter Pulse Intervals (IPI) reveal highly variable patterns that are clearly distinct before and after the dominance contest (Batista et al, 2012;Westby, 1975a;Zubizarreta et al, 2015). Two critical tasks are performed by using self-and conspecifc-generated electrical pulses and their feedback on fish's electrosensory system: electrolocation and electrocommunication (Black-Cleworth, 1970;Caputi et al, 2008;Castello et al, 2000;von der Emde, 2013).…”

“…While fish are contesting dominance, they may stop emitting pulses during variable time intervals ("offs") (Westby, 1975a,b). In some situations, instead of the stereotyped pulses, these fish can emit small electric field oscillations, known as "chirps" (Figure 2) (Batista et al, 2012;Zubizarreta et al, 2015). Offs and chirps are often related to submission (Batista et al, 2012), physical aggression and retreat.…”