(Ghostly) Animal of the day

© Monterey Bay Aquarium Research Institute


Name : Macropinna microstoma, more commonly known as the Barreleye of the Pacific is a species belonging to the Opisthoproctidae family (little Osmeriforme fish).

Habitat : Because it lives in the abyss of the Pacific, very deep in the ocean (500m to 1000m deep), this fish has never been seen alive… This mysterious fish has only been observed while greatly damaged or already dead ! Weird… isn’t it?

Size : The Barreleye is approximately 15 cm long (tail included).

Way of life : The Macropinna generally stays still and lets itself be carried by the current while staying somewhat stable thanks to its fins. It has a macrophage diet. The odd-headed fish has a tendency to steal its preys from Siphonophores, which are huge jellyfish (from the cnidarian family). Its food is mostly made of tiny fish, larva, jellyfish and other gelatinous animals. As for its reproduction, the Macropinna is an oviparous creature and the larva is planktonic one.

Drawn by Léa Prévost


While being known since 1939, this specimen was first photographed and filmed in its natural environment by the Monterey Bay Aquarium Research Institute (MBARI), off the coast of California in 2004.
But why is Macropinna so hard to observe ? Is it playing hard to get ?

The answer lies in its globular and transparent head. What makes its anatomy so special is the fact that its eyes are inside its skull! Its head is filled with a transparent gel that allows its tubular eyes to be fully mobile. The two green spheres that can be seen in its eyes are the crystalline lenses that filter light.
The two small orifices that we see are therefore not its eyes but its nostrils. This characteristic allows it to deceive its prey as well as its predators.

While its body is in a horizontal position, its upward-facing eyes can detect its prey despite having dim light around it. When hunting its prey, its eyes return to the front of the body. The olfactory organs of the little fish are found behind their eyes inside dark capsules.

This ingenious system that makes him a remarkable predator is unfortunately the reason why the little fish can never be brought to the surface alive.
Its transparent head that gives it its almost ghost-like appearance is very sensitive to pressure. The Barreleye are used to living in great depths under high pressure. When caught, its head explodes from the lack of pressure. This surprising phenomenon makes the study and observation of this fish quite difficult.

Written by Jennifer Jhon
Translated by Nour El Ghazal

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