Researchers have revealed that fish can detect and respond to fear in their counterparts, indicating a level of emotional complexity previously associated mainly with mammals. The study, published in the journal Science, identifies the hormone oxytocin as the key player in the contagious nature of fear among zebrafish, similar to its role in empathy in humans.
The research highlights that fear is not only a shared emotion among zebrafish but also that the brain region responsible for regulating this fear contagion bears similarities to the emotional centre found in mammalian brains. Ross DeAngelis, a postdoctoral researcher at the University of Texas, suggests that the conservation of oxytocinโs role in regulating empathetic behaviour raises intriguing possibilities about the evolutionary history of empathy, potentially extending beyond the last common ancestor shared by fish and humans around 375 million years ago.
In the experiments, zebrafish were divided into groups, and a substance triggering fear, such as erratic swimming, was introduced in a tank with multiple fish. Observations revealed that when a single fish was placed in a separate tank and witnessed its peersโ fearful reactions through glass, it responded by freezing, demonstrating a form of fear contagion. Genetically modified fish showed a reduced response, indicating the importance of oxytocin in the process. When these modified fish were administered oxytocin, their fear response was reinstated.
This study challenges previous notions about the emotional lives of fish and suggests that empathy, linked to oxytocin, may have deeper evolutionary roots than previously believed. The findings contribute to our understanding of the shared emotional mechanisms across diverse species.
Source: Science