Macropinna

Macropinna is a genus of marine ray-finned fish belonging to the family Opisthoproctidae. The genus currently contains only one described species, Macropinna microstoma, commonly known as the barreleye fish. This remarkable fish is distinguished by its transparent head and the unique tubular eyes that can rotate forward. The fluid-filled dome on its head is thought to protect its sensitive eyes from the stinging cells of jellyfish, which it preys upon.

The barreleye fish inhabits the deep waters of the Arctic, North Atlantic, and North Pacific oceans, typically found at depths between 600 and 800 meters. Its body is relatively small, usually not exceeding 15 centimeters in length. Its coloration is generally dark, helping it to blend into its deep-sea environment. The large, upward-pointing eyes are a prominent feature, allowing it to detect the faint silhouettes of prey against the dim light filtering from the surface.

The diet of Macropinna microstoma consists primarily of small crustaceans and jellyfish. Its ability to rotate its eyes forward allows it to pinpoint the location of prey even when its body is oriented differently. The transparent head is a key adaptation that enables this forward vision without obstruction. Despite its bizarre appearance, the barreleye fish is a fascinating example of the adaptations found in the extreme conditions of the deep sea.