by Stephen Beech via SWNS
Fish suffer from “social stress” – just like humans, according to a new study.
Researchers found that male fish with low status get so stressed out it impacts their brains.
They say their findings, published in the journal Frontiers in Behavioral Neuroscience, could in future help to treat human stress-related disorders.
American scientists showed that low-status male cichlid fish have higher levels of oxidative stress in their brain – which is linked to poorer mental and neurological health in humans.
They explained that social stress is a “prime suspect” in the accumulation of oxidative stress in the brain, which is believed to contribute to mental health and neurodegenerative disorders.
But little is known about the mechanisms that turn social stress into oxidative stress, and how social status affects it.
By studying cichlids – a highly social, very hierarchical fish species – scientists have now found that social stress raises oxidative stress in the brains of low-status fish.
Study lead author Dr. Peter Dijkstra, of Central Michigan University, said: “We found that low rank was generally linked to higher levels of oxidative stress in the brain.
“The patterns of oxidative stress in the brain are likely influenced by social experience modulating cellular processes in the brain.”
He explained that male cichlids have a strict, highly visible social hierarchy.
Dominant males, who have higher levels of androgen hormones, are bigger, more aggressive, and more colorful than subordinate males. They defend territories and court females.
Hormones such as androgens which are triggered by social stress have been linked to oxidative stress changes in several organs.
It makes cichlids, with stressful social lives tightly linked to androgen levels, ideal for studying the impact of social stress on oxidative stress levels.
The research team set up 15 tanks divided in two, and placed six females and two males in each experimental compartment, allowing each group of fish to interact freely and to visually interact with the neighboring group.
The team also added half a flowerpot to each compartment, to give the dominant male a territory to defend.
To quantify the cichlids’ behavior, the researchers filmed them and recorded the behaviors witnessed.
In all but two groups, the cichlids rapidly developed a hierarchy, which remained stable over the weeks of the experiment.
The research team eventually took blood samples from the male fish and dissected their brains, as well as measuring their size and length and the size of their gonads relative to their body. Larger gonads indicate higher levels of androgens.
In each division of each brain, they measured markers of oxidative stress and antioxidant capacity, which counteracts oxidative stress.
The researchers also measured the oxidant capacity and oxidative DNA damage present in each brain section.
They found that the low-status fish had higher levels of oxidative stress and lower antioxidant capacity than the high-status fish.
Although the higher-status fish had higher indicators for oxidative stress in their blood, their brains seemed to be protected.
Indicators of reproductive activity, associated with high status in the fish, were linked to higher levels of antioxidants and lower levels of oxidative stress in the brain.
The researchers said that could be linked to their levels of androgens, which can be neuroprotective in some cases.
Low-status fish had smaller gonads and therefore lower androgen levels.
The researchers said that the effects of status on oxidative stress are “complex”.
When they looked at markers of oxidative DNA damage and antioxidant capacity in different brain divisions, they found that different markers were differently impacted by social status.
Dr. Dijkstra said: “It’s important to note that the patterns detected relative to oxidative stress in the brain may not be ‘bad’ for the animal.
“Maybe in the future we will study the fitness consequences of oxidative stress in the brain.
“But showing that patterns of oxidative stress are linked to social stress is important, and may provide important insights into mechanisms by which social stressors promote oxidative stress and disease in the brain.
“Social competition in our cichlids is a great model system to understand how competition in our modern human societies influences important physiological functions.
“We compare ourselves to others continuously, and these problems are especially compounded by social media.
“But I would be hesitant to directly relate our findings to human societies.”
The researchers said that more targeted studies will be needed to understand the impact of the interplay between social stress and oxidative stress on specific brain regions.
Dr. Dijkstra added: “I think we just uncovered some interesting patterns across different divisions of the brain.
“The next step is to understand the regulation of oxidative stress better and how social stress influences this.
“This requires more rigorous experimental studies.”
