If you thought last week’s coelacanth was the the weirdest fish in the sea, you would be horribly mistaken. Although it may seem impossible, there is a fish lurking in the Earth’s oceans that is much more intriguing than the coelacanth. I present the barreleye fish.
The barreleye fish was discovered in 1939. These deep sea fishes prefer to live in tropical waters, and can grow up to six inches long. What really sets the barreleye apart from all other species is, unsurprisingly, its eyes. As its name suggests, the barreleye fish has barrel shaped eyes, also called tubular eyes. What’s even more interesting is where these tubular eyes are located: in its transparent head!
Why Have These Eyes?
Researchers believe the barreleye fish’s eyes are the way it is because it helps the fish hunt prey. As previously mentioned, the barreleye is a deep sea fish, so its prey are often times above it. By having tubular eyes, the barreleye can scan a wide area above itself in order to find food. The barreleye even has large fins to help stabilize itself when it’s doing it’s scanning! This, however, causes one major problem. If the fish’s eyes are fixed to always be looking up, then how does it eat? After all, trying to eat something while not being able to see one’s own mouth can prove to be rather difficult. As it turns out, the barreleye can actually rotate its tubular eyes within its clear head to see what is in front of it.
Another striking detail about the barreleye’s eyes is the fact that they are green. Scientists believe that this green pigmentation allows the fish to filter out sunlight to better spot prey such as bioluminescent jellies. According to a study by J. C. Partridge et al., certain species of barreleyes can both reflect and refract light, giving them tremendous eyesight. In fact, a certain species of barreleye, the Dolichopteryx longipes has the ability to look both up and down at the same time by reflecting light onto its retinas.
The See Through Head
Second to its tubular eyes, comes the barreleye’s transparent head. Researchers believe this head acts as protection for the fish’s precious eyes. Due to the barreleye hunting jellyfish, its eyes risk getting stung. In order to protect these integral organs, the barreleye evolved a covering over its eyes to act as protect goggles.
As mesmerizing as it is odd, the barreleye is definitely a deep sea oddity.