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Zebrafish Are Hopelessly Obsessed with Robotic Clones of Themselves

3D robotic replicas make it easier to study zebrafish, which make it easier to study human psychological disorders.
Image: Uri Manor, NICHD Flickr

Zebrafish would rather hang out with other zebrafish than with anything else, even if that means looking at robotic replicas of themselves.

A team of researchers at NYU Tandon School of Engineering, funded by the National Science Foundation, printed 3D robotic models of zebrafish to study how real zebrafish would react to the robots in comparison to other living organisms. The models not only looked like actual zebrafish, but were designed to move like them, too.

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"Our work is to help understand what the social determinants are at the basis of the behavior of zebrafish," lead researcher Maurizio Porfiri, professor of mechanical and aerospace engineering, told Motherboard. His team discovered that zebrafish react strongly to things that look and move like they do. The experiment also suggested that robotic zebrafish were ideal for studying zebrafish behavior, he added.

When you work with actual zebrafish, it's difficult to isolate a specific variable and quantify how that variable influences the animal. For example, if researchers wanted to understand how one zebrafish (the "experimental" fish) would react to the size of another zebrafish (the "stimulus" fish), they would also need to adjust for other variables that come along with increased size, such as personality, age, fitness, and so on. With robots, however, researchers can manipulate a single factor and control for the rest, said Porfiri.

"Utilizing robotics [offers] a consistent and repeatable stimulus, and reduces the number of animals used to test a hypothesis, an ethical advantage," he said. Meanwhile, the experiment proved which factors are important in getting zebrafish to effectively respond to robotic replicas of themselves: movement and appearance.

To test the robotic replicas, the team of researchers—two researchers with master's degrees, a Ph.D. student, an undergrad, and Porfiri—put live zebrafish in the middle of a tank divided into three sections, each separated by a transparent wall. The robotic fish were placed in the two outer sections of the tank. The researchers observed how the the live zebrafish swam from non-moving replicas to transparent replicas that moved, then to 3D replicas that moved in all directions programmed to swim like real fish, to 2D replicas that moved unnaturally in limited directions, and finally, to a stationary rod.

The researchers found that the live animals tried to imitate the motions of the 3D replicas. Meanwhile, they placed transparent barriers between the sections so the real zebrafish wouldn't try to interact directly with the robots.

The experiment illustrated that 3D replicas are a customizable, controllable and consistent tool to do many experiments with zebrafish, said Porfiri. And zebrafish themselves are an important tool and replacement for more complex animals like mice, for researchers to study human disorders like addiction, anxiety, schizophrenia, and autism.

Read more: Why the Zebrafish Has Become Biology's Supermodel

"Zebrafish have a lot of genetic similarities with humans, primarily in the context of diseases," said Porfiri. And now researchers might be able to study them more easily.