We’ve learned something new about the deep sea today, and it has a transparent head. The barreleye fish lives in the ocean’s twilight zone, and no that does not include Willaim Shatner seeing a creature out a plane window. The twilight zone is about 600 to 800 meters below sea level and is home to a host of interesting undersea animals. The barreleye fish is just one of many.
What makes the barreleye fish fascinating is its transparent head. It has two large green orbs for eyes that gaze upwards through its transparent head. The eyes sit on two long silvery tubes which give it its common name, the barreleye fish. The green-yellow tint on the eye-orbs allows the barreleye to easily spot bioluminescent prey. The pigments in the eyes act as filters between sunlight and bioluminescence.
A fish with a transparent head was discovered over 2000ft deep in the ocean. It can rotate it’s eyes to track prey. Nature really is amazing pic.twitter.com/VBHIfeQpf7— Today Years Old (@todayyearsoldig) September 2, 2022
But why do their eyes point directly upward? Bruce Robison, deep-sea biologist at the Monterey Bay Aquarium Research Institute in California, explains. “It always puzzled me that their eyes aimed upward, but the field of view did not include their mouths,” he told the Guardian. His team at MBARI was only able to research deceased specimens, until they finally got their hands on a live barreleye in 2008. Before that, scientists thought the eyes were fixed. But, they found out that wasn’t true.
“Suddenly the lightbulb lit and I thought ‘A-ha, that’s what’s going on!’” said Robison. “They can rotate their eyes.” In other words, they can track prey from all directions to right in front of their mouths.
Barreleye Fish With Transparent Head, Giant Eyes Stumps Researchers for Years
Additionally, Robison’s team was fascinated by the barreleye’s transparent dome. “It had this canopy over its eyes like on a jet fighter,” said Robison. For all the specimens the team had seen before, this part of the fish had been torn off when it was brought up to shore. It’s extremely delicate, and the force of being brought up in a net tore the shield. On the high-definition camera feed, the team got a look at the amazing components of the barreleye.
Apparently, the dome protects the fish’s eyes from predators and stinging siphonophores, which float in net-like groups. The barreleye fish sometimes steals food from these creatures, and it needs a protective barrier. The eyes are ultra-sensitive and let in a ton of light, as the barreleye lives in an area of complete darkness.
Though, it’s difficult to study the barreleye fish because they are seen so little alive and in the wild. Robison has only seen the barreleye about 8 times in 30 years. “We do spend a lot of time exploring down there, so I can say with some confidence that they’re quite rare,” said Robison.