Barreleye Fish

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Do you know this very strange fish, a curiosity of nature ? Macropinna microstoma or Barreleye. This is a small fish, 15 cm, which lives in fairly deep water, between 600 and 1000 meters deep.
What we see over its mouth, not the eyes, but the nostrils.
The Barreleye fish is particular because its eyes are not on its head, but inside it, at the bottom of small pipes  barrel-shaped. And as this fish eyes are inside the head, Nature found a trick so that it can see :  it simply has a transparent head !

transparent head fish

This translucent skull is filled with a transparent liquid in which eyes are mobile, looking upwards and forwards. We think that it usefull to spot the preys and to watch its predators.
This fish is known since 1939, but we ignored everything of the surprising transparent head: this one burst when raised on surface, because of the change of pressure. It is only from 2004 that the researcher Bruce Robison and Kim Reisenbichler from Monterey Bay Aquarium began to use the modern means of diving  to study Barreleye in his natural environment.

MBARI researchers Bruce Robison and Kim Reisenbichler used video taken by unmanned, undersea robots called remotely operated vehicles (ROVs) to study barreleye fish in the deep waters just offshore of Central California. At depths of 600 to 800 meters (2,000 to 2,600 feet) below the surface, the ROV cameras typically showed these fish hanging motionless in the water, their eyes glowing a vivid green in the ROV’s bright lights. The ROV video also revealed a previously undescribed feature of these fish–its eyes are surrounded by a transparent, fluid-filled shield that covers the top of the fish’s head.

This video is narrated by senior scientist Bruce Robison.

For more on this story, see MBARI’s news release at:
http://www.mbari.org/news/news_releases/2009/barreleye/barreleye.html