By Wil Longbottom for MailOnline
Updated: 13:57 BST, 25 February 2009
This amazing barreleye fish really does have eyes in the back of his head.
Accustomed to living in the pitch black of the deep sea, the animal has developed a unique and incredibly useful ability to spot predators trying to sneak up on it, as well as potential food – through its own head.
During its evolution, the Macropinna microstoma has developed so its head is transparent and its eyes are able to move themselves inside its own head to look out in different directions.
Eyes front: The barreleye fish has developed the unique ability to move its eyes inside its own head so it can spot predators and food in pitch black seas
Viewed from the front, the creature appears to be just like an average fish.
But the differences immediately become clear when looking at it from the side or from above.
While its body is mostly dark, the top part of its head is transparent, and its eyes are clearly visible.
Scientists believed the barreleye fish could only look upwards, but they have recently discovered the creature can also look forward to align its mouth with its eyes.
According to evolutionary biologists, it developed such a powerful sense of sight as a result of the harsh environment it lives in.
The fish, which is only a few inches long, lives a great depths just below the line to which sunlight can penetrate the water.
This means that creatures around it cannot see it clearly. Predators lurking above it cannot spot it either, but it can look upwards to hunt for the small fish and plankton it lives on.
Unique: The creature lurks at depths of up to 2,600ft where the sun cannot penetrate and when it spots smaller fish or plankton it attacks from the dark and swiftly engulfs its prey
When a suitable morsel is identified, the barrelfish attacks out of the darkness and swiftly engulfs its prey.
To avoid looking at the sun when it moves into shallower waters, the creature’s eyes can rotate to look forward so it can see where it is swimming.
Its amazing eyes glow a bright green and researchers believe it may have developed a form of light filter which allows it to ignore the sunlight and spot the bioluminescence of small fish and jellyfish – it’s favourite food.
The two holes which look like eyes on the front of the fish are in face nales, olfactory organs similar to human nostrils.
The barrelfish has a crystal clear liquid over its eyes, held in place by a tiny membrane.
If that was to break, its eyes would become exposed to the sea and the pressure that exists at its natural depths of between 2,000 and 2,600ft (600 to 800 metres) would instantly kill it.