Barreleye – A Fish with transparent head

A very bizarre looking deep-water fish called Barreleye that has a transparent head and tubular eyes. Even though the two spots above the fish’s mouth look like eyes they are not.

The barreleye (Macropinna microstoma) has extremely light-sensitive eyes that can rotate within a transparent, fluid-filled shield on its head. The fish’s tubular eyes are capped by bright green lenses. The eyes point upward when the fish is looking for food overhead. They point forward when the fish is feeding. The two spots above the fish’s mouth are olfactory organs called nares, which are analogous to human nostrils. Although the barreleye is facing downward, its eyes are still looking straight up.

All the species in the Opisthoproctidae family are known for having ultra-sensitive tubular eyes that face upward, well adapted for collecting light.

Using remote operate vehicles scientists were able to view the barreleyes in the ocean between 600 and 800m.  The found that the eyes of Macropinna can rotate within transparent shield that covers the fish’s head, allowing it to look at whatever it wants.

But the craziness of this fish doesn’t stop with the clear skull or pivoting eyeballs…

In addition to their amazing “headgear,” 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 . Their small mouths suggest that they can be very precise and selective in capturing small prey. On the other hand, their digestive systems are very large, which suggests that they can eat a variety of small drifting animals as well as jellies.