If you visit the aquarium often, the archerfish may even recognize you as a regular visitor!
If you become a regular visitor to the aquarium and say hello every time, there is one fish that may eventually remember your face: the archerfish.
The hypothesis that archerfish can distinguish human faces was proven by Oxford University zoologist Dr. Kate Newport and his colleagues. After training the fish in such a way that they would be rewarded with food if they chose a specific human face, they were able to choose the specific human with an 81% success rate when shown that face alongside another human face. In other words, they may be able to accurately distinguish between familiar and unfamiliar human faces. Archerfish were chosen as subjects for this experiment because they have the ability to squirt water from their mouths and hit targets accurately, which suggests that they may have excellent vision.
Furthermore, according to Professor Kawasaka, there are species of fish that can distinguish between each other's faces. Research suggests that ornamental fish called discus, which live in the Amazon River, may be able to identify each other by the patterns on their faces. Another fish that can distinguish between other fish in the same way is the false tropical damselfish, which we will introduce next.
Can the fake damselfish tell if customers are wearing makeup?
The false tropical damselfish may be the reason why people who wear foundation and sunscreen may appear to have brighter faces than other people.
Foundations and sunscreens often contain ingredients that reflect ultraviolet rays (UV scattering agents). The false tropical damselfish can sense ultraviolet rays that are invisible to humans, so it is possible that the UV rays reflected by foundations and other products appear dazzling to them.
Why does it have these characteristics? To begin with, there is another species called the tropical damselfish, which is so similar to the false tropical damselfish that it is indistinguishable (as you can guess from the name "fake"). The false tropical damselfish has a very strong sense of territory, and will violently attack any member of its species that tries to encroach on its territory. This is when it is necessary to distinguish between the identical-looking tropical damselfish and the false tropical damselfish, which is the same species.
The difference between them is ultraviolet light. The false damselfish has spots around its face that reflect ultraviolet light. Ulrike Siebeck, a researcher at the University of Queensland, focused on this and conducted the following experiment.
First, they prepared a transparent tube that allowed UV light to pass through and another that did not, and placed false damselfish in each. Then, when they placed a species of the same species with a territory on the outside of the tube, they attacked the tube that allowed UV light to pass through. In other words, those that could recognize the pattern because of the UV light were the same species, while those that could not see the pattern because the UV light was not shining through were either a different species or the same species with no intention of attacking.
Unfortunately, we humans cannot detect ultraviolet light and are therefore unable to see the changes in their patterns, but from their perspective, it may be obvious which parts of our faces are reflecting ultraviolet light.
Seahorses see different visitors with their right and left eyes!
Seahorses have a complex muscular structure in their eyes, allowing them to move each eye independently, like a chameleon. It may be possible for them to follow a couple on a date with their right eye, while using their left eye to follow a child glued to the tank in the opposite direction.
For those of us who cannot see different things with our right and left eyes, it is difficult to imagine what kind of landscape a seahorse's two fields of vision are reconstructed in their brains.
Professor Kawasaka also says that he cannot say for sure what the world is like for seahorses.
"Many fish have eyes on the left and right sides of their heads, and it is thought that they can see better from the side than from the front. However, can they simultaneously focus on what is reflected in their right and left eyes, or can they only be aware of one thing at a time, like we can? It is not clear how fish actually see different objects tracked by their left and right eyes, and this is not limited to seahorses."
What do they actually see and how do they perceive the world? This is a world unknown to us as humans. The various studies that Professor Kawasaka introduced showed that even within the same fish species, different species perceive the world around them differently. This is explained by the biological concept of the "Umwelt" (the world that each living thing perceives independently as its own unique time and space). The world that we normally perceive is perceived as a completely different world by other living things. Just like how humans and dogs perceive things differently, even when they are in the same space.
The experiments introduced here prove that fish behave in this way after training or under certain circumstances. Still, if you imagine that maybe fish see the world in this way, you'll enjoy your aquarium in a different way than usual. The next time you visit an aquarium, try to imagine the world as perceived by fish.
