The fish with glass head: Barreleye fish

You will not believe it until you see it for yourselves, a deep-water fish species with translucent head. It is known as the Barreleye Fish, commonly recognized as spook fish with the scientific name of Macropinna microstoma. And it is a true natural wonder.

It was first discovered by a marine biologist back in 1939. Unfortunately, no one recognized it had a transparent head until 2004 where the first photograph of the fish with its translucent head was taken.




It is typically found between the depths of 2,000 and 2,600 feet, but it has been found as deep as 3,330 feet.  This small fish can be found in the world’s three main oceans: Pacific, Atlantic, and Indian Ocean. The species can grow up to 44 centimeters or 17.3 inches in length, with an average size of about 15 centimeters (6 inches).




Among deep sea species, the Barreleye Fish has one of the rarest appearances. The dome-shaped head (filled with clear fluid), which is transparent on top, is the first thing that one sees. Embedded with two barrel-shaped or tubular eyes, they continue to point upward. Previously, it was thought that the eyes were fixed in that location and they are hypersensitive, with a green fluid capable of absorbing even the tiniest bit of light at the great depths where it lives. The fish is thought to be able to block out any sunlight that gets in, allowing them to see bioluminescent light produced by jellies and other sea creatures.

The mouth of the Barreleye Fish is very thin, implying that it is picky about what it eats. The snout is pointed and has a narrow mouth with empty of teeth. The fish’s body is dark brown, and its fins are broad and silvery.

Two tiny eye-like spots are located just above its mouth. They are not, though, the eyes. They are essentially the fish’s olfactory organs. If we make a comparison, they are identical to human nostrils.

The Barreleye Fish has big, flat fins, which is one of their most amazing adaptations. In deep waters, these fins allow the fish to remain completely motionless. They are also designed to allow it to perform specific maneuvers while searching for food.

Barreleye Fish is an ambush predator. They remain immobile at deep levels in the water and look upward. They have specially designed eyes that give them binocular vision.

What do they eat?

When it comes to Barreleyes’ diet, scientists have discovered fragments of cnidarian animals (a phylum of over 10,000 animal species) and jellyfish in the stomachs of this fish. Barreleye Fish encompasses a wide range of organisms, including zooplankton (both gelatinous and crustacean), siphonophore tentacles and nematocysts, small fish, and so on.


Barreleye Fish is pelagic spawners. Females will lay eggs in water, and males will release sperm in the water. In the water, the eggs are fertilized. And are planktonic and buoyant in nature. They will float about in shallow water, drifting with the current. They will eventually step deeper as they mature into adults.

One fun fact about the Barreleye Fish is that the fish is blind on the sides. That is, it is unable to see in both directions. It has the ability to see upward and forward. This occurs because the eyes are fixed in place, allowing for forward and upward swiveling movement. Yeah, the fish is devoid of cone cells.

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