Fish species checks body size in mirror – and scientists say it’s the first animal to have ‘self-awareness and goals’

A FISH species examines itself in the mirror before deciding whether to fight in what scientists call the first instance of animal self-awareness.

The bluestreak cleaner wrasse is native to the waters off Japan and Eastern Africa.

The tiny fish grows no more than 10 centimeters long but occupies a unique niche in the sea.

Groups of wrasses operate "cleaning stations" where they service other fish, or "clients," by eating parasites off their bodies.

And new research shows this remarkable fish may exhibit a human level of intelligence.

A team of researchers from Osaka Metropolitan University discovered that the fish check their reflection in a mirror before deciding whether to attack adversaries who are bigger or smaller than themselves.

The results, published in Scientific Reports, indicate that the fish try to predict the outcome of a fight by comparing their body size to that of their rivals.

Researchers say it is the first time a non-human animal has shown evidence of mental states like body image, intentions, and goals.

These are all elements of private self-awareness, or the ability to understand and perceive your emotions and thoughts.

And this isn't the researchers' first run-in with fishy intelligence.

Last year, they learned that the cleaner wrasse could identify photographs of itself.

Researcher Masanori Koda described the fish as having "a kind of self-consciousness to recognize themselves."

The fish were shown images of themselves that had been altered so stains representing parasites colored their throats.

After viewing the photos, the fish scrubbed their throats against sand and other objects as if trying to remove the parasites.

The fish were shown four types of photos, including images of their faces superimposed on the bodies of other fish. Whenever their faces appeared, the fish did not attack.

And that isn't all - an earlier study showed the fish could recognize themselves in a mirror.

At first, the wrasse attempted to fight the mirror, mistakenly thinking it was a rival.

However, the behavior ceased after the fish swam upside down in front of the mirror and watched its reflection copy the maneuvers.

This evidence, coupled with the latest study, indicates the wrasse possesses higher-level intelligence.

Beyond recognizing its own appearance, the behavior indicating that the fish was trying to predict the outcome of a fight demonstrates human-like comprehension.

And the researchers believe their findings have implications for science at large.

“The results that fish can use the mirror as a tool can help clarify the similarities between human and non-human animal self-awareness and provide important clues to elucidate how self-awareness has evolved,” OMU Graduate School of Science student Taiga Kobayashi said.

What is the bluestreak cleaner wrasse?

The bluestreak cleaner wrasse (Labroides dimidiatus) is a small, colorful fish commonly found in the coral reefs of the Indo-Pacific region.

It’s renowned for its role as a "cleaner fish," which means it feeds on parasites and dead skin from other fish.

The fish have been observed to operate "cleaning stations" where they beckon to other fish by waving their bodies.

The species has a distinctive blue and black coloration with a prominent blue stripe running along its body. Scientists believe this horizontal stripe indicates to other fish that they are "cleaners."

By attracting larger fish to come to them for cleaning, the cleaner wrasses get a meal - an example of a mutualistic relationship where both parties benefit.

Their cleaning behavior is also crucial for maintaining the health of the reef ecosystem.