Barreleye
Macropinna microstoma
- Not on exhibit
- Animal type
- Fishes
- Ecosystem
- Deep sea
- Relatives
- Barreleyes, smelts; Order: Osmeriformes
- Diet
- Zooplankton, including crustaceans and siphonophores
- Range
- From 2,000 to 2,600 feet (600–800 m) in the northeastern Pacific Ocean
- Size
- Up to 6 inches (15 cm) in length
Meet the barreleye
This peculiar fish is known for its strange eyes—two bright green upward-pointing orbs that are visible through the transparent dome on its forehead. The upward-pointing eyes are able to spot prey above them in the water column but can rotate forward when needed.
Natural History
Barreleyes live in the ocean’s twilight zone—a depth where the sunlight from the surface fades into darkness. Its ultra-sensitive eyes look up to see the silhouettes of its prey.
Diet
The barreleye’s diet consists primarily of zooplankton. Based on what they find in the fish’s stomach contents, scientists believe that the barreleye may eat crustaceans trapped in the tentacles of siphonophores. With its eyes pointed upwards, the barreleye sees through its transparent head and spots prey swimming above it in the water column. Scientists originally believed that the fish’s eyes were fixed looking straight up. But in 2009, MBARI researchers discovered that the barreleye can actually rotate its eyes towards the front so it can see its food while eating.
Size
The barreleye is actually quite small, usually up to six inches (15 centimeters) long.
Habitat
Barreleyes are thought to be solitary creatures that inhabit the ocean’s twilight to midnight zones, usually between 2,000 to 2,600 feet (600 and 800 meters).
Did you know?
- In addition to their amazing eyes, barreleye fish have large, flat fins which allow them to precisely maneuver, as well as remain almost completely motionless in the water.
- In more than three decades of deep-sea research, MBARI's remotely operated vehicles (ROVs) have logged more than 5,600 dives, yet as of 2022, they've only encountered this fish nine times.
Reproduction
Little is known about barreleye reproduction. However, researchers believe that barreleye fish are pelagic spawners – eggs and sperm are released directly into the water.
Conservation
Anything that ends up in the ocean may eventually make its way to the deep sea. It is important to remember that the creatures living in the darkness of the deep sea are affected by what we do on land.
Learn more about the barreleye and MBARI's discoveries on MBARI.org
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