The Decision to Fight or Flee – Insights into Underlying Mechanism in Crickets

Abstract

Ritualized fighting between conspecifics is an inherently dangerous behavioral strategy, optimized to secure limited resources at minimal cost and risk. To be adaptive, potential rewards, and costs of aggression must be assessed to decide when it would be more opportune to fight or flee. We summarize insights into the proximate mechanisms underlying this decision-making process in field crickets. As in other animals, cricket aggression is enhanced dramatically by motor activity, winning, and the possession of resources. Pharmacological manipulations provide evidence that these cases of experience dependent enhancement of aggression are each mediated by octopamine, the invertebrate counterpart to adrenaline/noradrenaline. The data suggest that both physical exertion and rewarding aspects of experiences can activate the octopaminergic system, which increases the propensity to fight. Octopamine thus represents the motivational component of aggression in insects. For the decision to flee, animals are thought to assess information from agonistic signals exchanged during fighting. Cricket fights conform to the cumulative assessment model, in that they persist in fighting until the sum of their opponent’s actions accumulates to some threshold at which they withdraw. We discuss evidence that serotonin, nitric oxide, and some neuropeptides may promote an insect’s tendency to flee. We propose that the decision to fight or flee in crickets is controlled simply by relative behavioral thresholds. Rewarding experiences increase the propensity to fight to a level determined by the modulatory action of octopamine. The animal will then flee only when the accumulated sum of the opponent’s actions surpasses this level; serotonin and nitric oxide may be involved in this process. This concept is in line with the roles proposed for noradrenaline, serotonin, and nitric oxide in mammals and suggests that basic mechanisms of aggressive modulation may be conserved in phylogeny.

Contest experience enhances aggressive behaviour in a fly: when losers learn to win

“…Results demonstrated that the enhanced fighting performance of both winner and loser males was influenced by merely experiencing a previous contest, regardless of the outcome or even the occurrence of physical contact in previous contests. In the olive fruit fly, the experience of winning without physical combat evoked a behavioural effect similar to that detected in crickets, as in both species this experience alone is sufficient to enhance aggression and prolong fight duration in subsequent male-male contests 10 . This has an interesting parallel in humans, as it has been demonstrated that watching a previous victory raises the level of the aggression-promoting hormone testosterone 59 .…”

“…Aggressive behaviour can be severe between individuals of the same species, as they compete for the same food, territory, and access to mates 6 . Game theory predicts that Evolutionarily Stable Strategies for conflicts between conspecifics may involve stereotyped contests characterized by the ritualised exchange of agonistic signals 7 , which are thought to convey increasingly accurate information for assessing the contenders' chances of winning [8][9][10][11] . Probability of winning can depend on physical disparities (e.g.…”

“…In several vertebrate species depressed plasma testosterone levels accompany defeat, and lower 11-ketotestosterone levels have also been observed 4,36,41 . In invertebrates, serotonin (5HT), nitric oxide (NO) and selected peptides affect the tendency to flee, avoiding further contests 10,42 . To date, relatively few model systems have been developed to shed light on how previous experience modifies aggressive behaviour in arthropods, mainly crickets 26 , drosophilid flies 43 and ants 28 (see also recent reviews 4,9,22,44 ).…”

Multiple cues produced by a robotic fish modulate aggressive behaviour in Siamese fighting fishes

“…Game theory predicts that evolutionarily stable strategies for conflicts occurring between conspecifics, may involve stereotyped contests featured by the ritualized exchange of agonistic cues 43, 44 . In this study, we investigated biomimetic aggressive interactions involving the Siamese fighting fish, Betta splendens (Regan) (Perciformes: Osphronemidae), and a conspecific-mimicking robotic fish in an open-loop agonistic interaction.…”

Targeted gene delivery in the cricket brain, using in vivo electroporation

“…Most studies, for example, those on escape behavior, phonotaxis, aggression and associative learning, have relied on electrophysiological, pharmacological and neuroimaging methods (Hedwig, 2006;Matsumoto and Mizunami, 2002;Ogawa et al, 2006;2008;Stevenson and Rillich, 2012). In spite of the many studies into a broad repertoire of behavior, the molecular basis that underlies these traits is still unclear.…”