Department of Biology, Stanford University, CA, USA.
Biol Lett. 2010 Dec 23;6(6):744-7. doi: 10.1098/rsbl.2010.0247. Epub 2010 May 12.
Fish act aggressively towards their mirror image suggesting that they consider it another individual, whereas in some mammals behavioural response to mirrors may be an evidence of self-recognition. Since fish cannot self-recognize, we asked whether they could distinguish between fighting a mirror image and fighting a real fish. We compared molecular, physiological and behavioural responses in each condition and found large differences in brain gene expression levels. Although neither levels of aggressive behaviour nor circulating androgens differed between these conditions, males fighting a mirror image had higher immediate early gene (IEG) expression in brain areas homologous to the amygdala and hippocampus than controls. Since amygdalar responses are associated with fear and fear conditioning in other species, higher levels of brain activation when fighting a mirror suggest fish experience fear in response to fights with a mirror image. Clearly, the fish recognize something unusual about the mirror image and the differential brain response may reflect a cognitive distinction.
鱼会对自己的镜像表现出攻击性，这表明它们将镜像视为另一个个体，而在一些哺乳动物中，对镜子的行为反应可能是自我认知的证据。由于鱼类无法自我识别，我们想知道它们是否能够区分与镜像战斗和与真实鱼类战斗。我们比较了每种情况下的分子、生理和行为反应，发现大脑基因表达水平存在很大差异。尽管这些情况下的攻击性行为水平或循环雄激素没有差异，但与对照组相比，与镜像战斗的雄性的大脑中与杏仁核和海马体同源的区域的即时早期基因（IEG）表达更高。由于在其他物种中，杏仁核反应与恐惧和恐惧条件反射有关，因此与镜像战斗时大脑激活水平更高表明鱼类会对与镜像的战斗产生恐惧。显然，鱼能够识别出镜像的某些不寻常之处，而大脑的差异反应可能反映了认知上的区别。
