At a depth of 600 meters, researchers filmed a fish whose eyes are visible through the top of its head.
Its scientific name is Macropinna microstoma. It has a small mouth, large fins and, above all, two green eyes protected by a transparent dome. Contrary to what one might think, this dome is not a glass skull: it is a flexible membrane covering the eyes.
The barreleye fish (Macropinna microstoma) lives in the ocean’s twilight zone, scanning the waters for food. After spotting potential prey, its large tubular eyes pivot beneath its transparent head to follow it.
Image: © 2026 MBARI
Scientists from the Monterey Bay Aquarium Research Institute in California encountered this animal during an expedition about 90 kilometers off the coast. Their underwater robot was returning to the surface when a researcher spotted it on the screens. The crew immediately gathered to witness this unusual sighting.
This fish has been known for a long time, but it remains extremely difficult to encounter. In nearly 40 years of exploration and around 7,000 robotic dives, MBARI teams have observed it only eleven times. This time, they were able to follow it for about twenty minutes and film it in 4K resolution for the first time.
Why does it have such unusual eyes? In the part of the ocean where it lives, sunlight barely reaches. The fish often remains almost motionless and looks upward. This allows it to see the silhouettes of small prey passing in front of the faint light from the surface.
But its eyes are not fixed in this position. They can pivot forward to follow prey as it approaches. The transparent dome also protects them from contact with the organisms it encounters while searching for food.
In the images, two small black dots are visible above the mouth. They might be mistaken for eyes, but they are actually organs used for smell. The real eyes are the two green structures visible behind the transparent membrane, slightly higher up in the head.
The robot also recorded three-dimensional images, making it possible to observe the animal from several angles. The scientists did not capture it. They hope these sequences will help them better understand its vision and how it moves in almost complete darkness.
This encounter shows how difficult the ocean depths remain to explore. Even with thousands of hours of video, some animals allow themselves to be observed only very rarely.