Pacific barreleye fish

Barreleyes, also known as spook fish (a name also applied to several species of chimaera), are small deep-sea argentiniform fish comprising the family Opisthoproctidae found in tropical-to-temperate waters of the Atlantic, Pacific, and Indian Oceans.

These fish are named because of their barrel-shaped, tubular eyes, which are generally directed upwards to detect the silhouettes of available prey; however, according to Robison and Reisenbichler, these fish are capable of directing their eyes forward, as well.

The bioluminescent organs of Dolichopteryx and Opisthoproctus, together with the reflective soles of the latter, may serve as camouflage in the form of counterillumination. This predator avoidance strategy involves the use of ventral light to break up the fishes' silhouettes, so that (when viewed from below) they blend in with the ambient light from above.

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For the first time, a large Pacific barreleye fish - complete with transparent head - has been caught on film by scientists using remotely operated vehicles at the Monterey Bay Aquarium Research Institute. The deep-sea fish's tubular eyes pivot under a clear dome.

 

The Pacific Barreleye fish gets its name from large eyes that are literally shaped like barrels, topped with beautiful green lenses. Also known as the Macropinna microstoma, its head is completely transparent, filled with fluid. This unique creature lives at depths of around 2000 to 2,600 ft. The Pacific Barreleye's see-through head may seem weird, but it has a very clear purpose -- to help it see better in the dark waters that it inhabits.

The Barreleye's eyes have been found to be incredibly sensitive, snapping up any stream of light available. Unlike most other fish, both the eyes are in the front of the head and point in the same direction, which gives it amazing binocular vision.

So the Barreleye is able to spot faint objects that other fish cannot, making it a feared predator. It's extremely fascinating, how it searches for prey. It starts off by staying still, eyes pointed upward in search of prey.

Sometimes the eyes are rotated to face forwards, or the eyes are still and the body is rotated so that the mouth is pointing in the same direction as the eyes. When tiny silhouettes of prey are spotted, the Barreleye moves in exactly the same direction to catch them.

Its flat, horizontal fins help it to swim very precisely. This method is so efficient that it is sometimes able to even snatch food away from the stinging tentacles of other deep sea creatures. Its mouth is really tiny so that's of great help as well, and the transparent shield makes it immune to stings.