If you're not really into salt-water tanks or don't spend a lot of time in coral reefs, there's still a high probability you may have heard of the bluestreak cleaner wrasse fish. Likely because last year it passed the "mirror test", showing that it can recognize its own face in a mirror. Now researchers have found there's much more to it than we thought.
The bluestreak cleaner wrasse is just one of about 600 different species of wrasse. It's a little thing, about 3.9 inches (10 cm) long on average, with, well ... a blue streak down its side.
The bluestreak cleaner wrasse exhibits all sorts of interesting behaviors and characteristics. They're called cleaner wrasse because they remove parasites, dead skin and mucus from other fish, often larger predator fish, in what's known as a symbiotic relationship. They're social fish and will often work in tandem or groups. Generally, a larger male will be the territorial leader and, should the dominant male die, the biggest female of the group can change sex to male and take over operations.
What might be even more remarkable (if something could possibly be more remarkable than physically mutating from one gender to another because nature says it's necessary) is that last year, a team of biologists from the Osaka Metropolitan University (OMU) in Japan found that the bluestreak fish can recognize itself in a mirror.
And even more than that, days ago, researchers discovered that it will look in a mirror to size itself up and debate whether to attack a rival fish. This means this fish exhibits behaviors showing private self-awareness traits in a way not found outside of humans: body image, intent, goals and standards.
Last year, prior to the fish being shown themselves in a mirror, the bluestreak were shown photographs of themselves and strange fish and the bluestreaks would attack, as they're incredibly territorial. Once shown the mirror and the fish began to recognize itself, it would no longer attack photos of itself, but would still attack strange fish.
When shown a photo with a mark made on the throat of the bluestreak, the fish would then exhibit throat-scraping behaviors, as if in effort to remove whatever foreign thing it believed to be stuck to its throat.
To really put it to the test, the biologists Photo-shopped a composite of the bluestreak's head/face onto a strange fish body, and again, the bluestreak would not attack that image, but would still attack strange fish as well as a composite of the bluestreak's body with a strange fish face/head on it.
The bluestreak could recognize its own face.
In the latest findings by researchers at the Osaka Metropolitan University, researchers presented bluestreaks that hadn't yet achieved mirror self-recognition (MSR) with photos of two other fish of the same species. One 10% smaller and one 10% larger than the "un-enlightened" bluestreak. Being aggressively territorial, the bluestreak would attack both fish in the photos with equal ferocity.
After passing the MSR test, the bluestreak would avoid aggression towards the larger photo-fish, while still attacking the smaller one without revisiting the mirror, suggesting a self-awareness of its own body size via memory of its mental image alone.
The bluestreaks that were accustomed to seeing themselves in the mirror would often revisit the mirror when presented a photo of a larger-than-they fish, presumably reassessing how tough it is, before making the decision to attack or not.
There are several animals that have passed the "mirror test". It's a simple test where a mark is put on an animal in a spot that can only be seen in a mirror, like a mouse's forehead. If the animal uses the mirror to try to remove or investigate the mark, they effectively pass. It shows that the animal has public self-awareness and self-recognition, at the very least.
Private self-awareness is entirely different. Private self-awareness shows that the animal likely possesses the ability to reflect (no pun intended) on its own sense of being without external stimulation – like a mirror – even if rudimentary compared to the ability of humans. But although it may seem rather elementary to us humans, we don't usually pass the mirror test until around 18 to 24 months.
The list of animals to have passed the mirror test is very, very short. The list of animals to exhibit private self-awareness is even shorter, so the bluestreak appears to be 'punching above its weight' in this regard.
The study was published in the journal Nature.
Source: OMU
