Even the phrase “seeing is believing” is not enough when looking at this astonishing fish! Meet Macropinna microstoma, commonly known as the “barreleye”. Barreleye fish have a transparent head with large internal eyes that are able to look upward. Living at depths of 600 to 800 meters below the surface, these ultra-sensitive eyes help these fish search for the faint silhouettes of prey overhead.
These fascinating fish were first described in 1939. However, only recently researchers found that the fish’s eyes aren’t fixed in place, but can rotate behind the transparent shield on the barreleye’s head. This allows the Barreleye to peer up at potential prey or look forward when the fish is feeding. The two spots above the fish’s mouth are olfactory organs which are analogous to human nostrils.
In addition to their amazing eyes and heads, barreleyes have a variety of other interesting adaptations to deep-sea life. Their large, flat fins allow them to remain nearly motionless in the water and to maneuver very precisely.
Barreleyes share their deep-sea environment with many types of jellyfish, of which the most common ones grow over 10 meters and trail thousands of stinging tentacles. Scientists speculate that the fish’s special rotating eyes to help them carefully maneuver among the tentacles, while the translucent head would protect the fish’s eyes from the jellies stinging cells.