Departamento de Fisiologia, Instituto de Biociências, Caunesp, UNESP, Botucatu, São Paulo, Brazil.
Zoology (Jena). 2011 Dec;114(6):335-9. doi: 10.1016/j.zool.2011.07.001. Epub 2011 Oct 4.
Eye darkening has been linked to social status in fish. The subordinate's eyes darken, while the eyes of the dominant fish become pale. Although this phenomenon has been described in salmonid fishes and in the African cichlid Nile tilapia Oreochromis niloticus, it is unclear whether eye darkening correlates with a reduction in aggressive behaviour. Thus, we evaluated the link between social status and eye darkening. We evaluated whether the eye colours of subordinate fish correlate with the frequency of received attacks in a neotropical fish, the pearl cichlid Geophagus brasiliensis. We paired pearl cichlids and quantified both the aggressive behaviour and the eye darkening of each fish. As has been described for Nile tilapia and Atlantic salmon, a clear-cut hierarchical relationship formed, where dominance and subordination were associated with pale and dark eye colours, respectively. Initially, eye colour darkening was positively correlated with the frequency of received attacks; however, a negative association occurred following eye darkening, in which the intensity of aggressive interactions decreased. Thus, fish that initially received a high number of attacks signalled subordination more rapidly and intensely (rapid and dramatic eye darkening), thereby inducing a negative social feedback mechanism that led to reduced aggression.
眼睛变暗与鱼类的社会地位有关。从属个体的眼睛变暗，而支配个体的眼睛则变得苍白。尽管这种现象在鲑鱼和非洲慈鲷尼罗河鲈鱼 Oreochromis niloticus 中已有描述，但眼睛变暗是否与攻击性行为的减少相关尚不清楚。因此，我们评估了社会地位和眼睛变暗之间的联系。我们评估了从属鱼的眼睛颜色是否与新热带鱼珍珠丽鱼 Geophagus brasiliensis 中受到攻击的频率有关。我们将珍珠丽鱼成对饲养，并量化了每只鱼的攻击性行为和眼睛变暗情况。与尼罗河鲈鱼和大西洋鲑鱼的描述一致，形成了明确的等级关系，其中支配和从属与眼睛的苍白和深色分别相关。最初，眼睛颜色变暗与受到攻击的频率呈正相关；然而，眼睛变暗后会出现负相关，此时攻击性相互作用的强度会降低。因此，最初受到大量攻击的鱼更快、更强烈地表现出从属（快速、剧烈的眼睛变暗），从而诱导出一种负的社会反馈机制，导致攻击性降低。
