Song Cha-Kyong, Herberholz Jens, Edwards Donald H
Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
J Exp Biol. 2006 Apr;209(Pt 7):1355-63. doi: 10.1242/jeb.02126.
Crayfish fight and form a dominance hierarchy characterized by a pattern of repeated agonistic interactions between animals with a consistent outcome of winner and loser. Once a dominance hierarchy is established, dominant animals display an elevated posture with both claws held laterally and forward, whereas subordinate animals display a more prone posture with both claws extended forward and down. Dominant animals behave aggressively towards the subordinate opponent, often approaching and attacking, whereas subordinate animals behave submissively by tailflipping and retreating. To evaluate whether the differences in social behavior are accompanied by differences in responses to non-social stimuli, we exposed socially naïve and experienced crayfish (Procambarus clarkii) to an unexpected touch in different social conditions. Socially naïve animals turned to confront the source of a unilateral touch with raised claws and elevated posture. Dominant animals also turned to face the stimulus source with raised claws and elevated posture, both when tested alone and in the presence of a subordinate opponent. Subordinate animals displayed this orienting response only while separated from their dominant partners. When paired with their dominant partners, subordinates avoided the stimulus source by walking rapidly forwards or backwards. When the subordinate animals were later tested again, first while semi-separated from the dominant and later while fully separated, they displayed a mixed pattern of avoidance and orienting responses. These results indicate that the behavioral responses of subordinate crayfish to touch depend on their social status, their current social conditions and their recent social history.
小龙虾会争斗并形成一种优势等级制度，其特征是动物之间反复进行争斗性互动，结果总是有赢家和输家。一旦优势等级制度建立起来，占主导地位的动物会呈现一种抬高的姿势，双螯横向且向前伸展，而从属动物则呈现一种更趴伏的姿势，双螯向前向下伸展。占主导地位的动物对从属对手表现出攻击性，常常靠近并攻击，而从属动物则通过翻转尾巴和后退表现出顺从。为了评估社会行为的差异是否伴随着对非社会刺激反应的差异，我们在不同社会条件下，让没有社交经验和有社交经验的小龙虾（克氏原螯虾）接受意外触摸。没有社交经验的动物会转身，以抬起的螯和抬高的姿势面对单侧触摸的来源。占主导地位的动物，无论是单独测试还是在有从属对手在场的情况下，也会以抬起的螯和抬高的姿势转身面对刺激源。从属动物只有在与占主导地位的伙伴分开时才会表现出这种定向反应。当与占主导地位的伙伴配对时，从属动物会通过快速向前或向后行走来避开刺激源。当从属动物后来再次接受测试时，先是半分开于占主导地位的动物，后来完全分开，它们表现出回避和定向反应的混合模式。这些结果表明，从属小龙虾对触摸的行为反应取决于它们的社会地位、当前的社会条件和近期的社会经历。
