Stevenson Paul A, Rillich Jan
Institute for Biology, University of Leipzig Leipzig, Germany.
Front Neurosci. 2012 Aug 21;6:118. doi: 10.3389/fnins.2012.00118. eCollection 2012.
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.
同种个体间的仪式化争斗是一种本质上危险的行为策略，其经过优化以最低的成本和风险获取有限的资源。为了具有适应性，必须评估攻击行为的潜在回报和成本，以决定何时战斗或逃跑更为合适。我们总结了对田间蟋蟀这一决策过程潜在机制的见解。与其他动物一样，蟋蟀的攻击性会因运动活动、胜利以及拥有资源而显著增强。药理学操作提供了证据，表明这些经验依赖性攻击增强的情况均由章鱼胺介导，章鱼胺是肾上腺素/去甲肾上腺素在无脊椎动物中的对应物。数据表明，体力消耗和经历的奖励方面均可激活章鱼胺能系统，从而增加战斗的倾向。因此，章鱼胺代表了昆虫攻击行为的动机成分。对于逃跑的决策，动物被认为会评估战斗期间交换的争斗信号中的信息。蟋蟀争斗符合累积评估模型，即它们会持续战斗，直到对手行动的总和累积到某个阈值，此时它们才会撤退。我们讨论了血清素、一氧化氮和一些神经肽可能促进昆虫逃跑倾向的证据。我们提出，蟋蟀战斗或逃跑的决策仅由相对行为阈值控制。奖励性经历会将战斗倾向提高到由章鱼胺调节作用所决定的水平。然后，只有当对手行动的累积总和超过这个水平时，动物才会逃跑；血清素和一氧化氮可能参与了这个过程。这一概念与哺乳动物中去甲肾上腺素、血清素和一氧化氮所起的作用相一致，表明攻击性调节的基本机制在系统发育中可能是保守的。
