When zebrafish were bred for certain personality traits — such as boldness or shyness — they exhibited changes in “unrelated” traits such as body shape and locomotion.

This new research from the North Carolina State University is potentially useful in animal breeding, pest management, as well as studying different human behaviors.

Senior study author and assistant professor Brian Langerhans said their data showed a connection among supposedly disconnected traits in animals.

“[These behaviors] can be associated — genetically correlated — with other traits that one might think are independent of such behaviors, like body shape and swimming abilities,” he explained.

In the experiment, various zebrafish lines were selected to be either bolder or to stay still, and the effects were measured based on how long they took to acclimate to their new surroundings.

Those selectively bred to be bolder displayed other traits: sleeker, more slender body shapes, as well as the ability to dart more rapidly through the water when startled compared with fish bred to be more shy.

Langerhans pointed to pleiotropy, where a gene affects two or more phenotypes, as a possible explanation for the link between personality and locomotion.

A separate phenomenon called linkage disequilibrium — where recurrent natural selection acts on a mix of traits – may be at work behind personality and body shape. For instance, being sleeker may assist these fish in surviving adulthood or reproducing more successfully.

It is crucial to understand how animals evolve these traits in an interconnected way versus in isolation, he added.

The findings are detailed in the journal Animal Behaviour.

A separate study revealed that sharks maintain different personalities just like humans do: some showed proof of shyness, while others seemed to be better and more inclined at risk-taking. There are sharks, too, that appeared less able to handle stress than others.

Scientists have identified up to 200 different animals — including mammals, fish and birds — with evidence of having personalities. Many of these creatures appeared to be bold, for example, which they likely apply at varying levels to foraging, mating and other aspects of their lives.

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