Episode 143 – Barreleye: The Spookiest Fish

“…and today we’re talking about a mysterious organic, deep-diving submarine. But more on that later.”

Deep down at the bottom of the ocean, there sits an alien monster fish that stares up straight through its own skull to spy prey: the barreleye. How does it do this? By being one of the weirdest creatures alive, even for deep-sea animals—and that’s saying something! But looking strange is just a fortunate side effect of being an empty-headed harbinger of jellyfish death from below here in LDT.

Description of the Barreleye

  • It’s important to approach survival in the open sea with a clear head, and this fish does… literally.
  • This open-minded fish has a shiny dome that you can just go ahead and look inside.
  • However, it’s been really difficult for people to get a good look at this oceanic organism. The first time we even got a live pic of this fish was in 2004. 
  • This ghostly guppy has a classic fish shape with a rounded head with broad bass-like fins. 
  • Its scaly body is a dark brown, but it’s bulbous head is clear with an array of internal colors coming through, particularly blues and greens. 

Measure Up

Welcome to the beloved Measure Up segment. The official listener’s favorite part of the show! The part of the show when we present the animal’s size and dimension in relatable terms through a quiz that’s fun for the whole family. It’s also the part of the show that’s introduced by you when you send in audio of yourself saying, singing, or chittering the words “measure up” into ldtaxonomy at gmail dot com.

  1. Common Crow
  2. Ring-billed Gull
  3. Chinstrap Penguin
  4. Beluga Whale 


  • 10 cm (4 inches)
  • How many microstoma go into the length of Clear Lake in California?
  • Hint: Clear Lake is in Lake County, CA. It was once much bigger but volcanic eruptions are thought to have separated it from the Blue Lakes to the North. 
  • 300,960 fish. Clear Lake is 19 mi (31 km) long and 8 mi (13 km) wide.

Dive Depth

  • 800 meters (2,600 ft)
  • How many fathoms is that?
  • Hint: A fathom is an old English unit of measurement that was widely used in nautical measurement. 
  • 433.3 fathoms. A fathom is 6 feet.

Fast Facts About the Barreleye

This mystery fish has baffled researchers since it was first discovered in 1939. Live specimens weren’t photographed until 2004 and early drawings failed to capture the fish’s transparent dome. Plus, when the fish is brought up from its normal depths, the dome is destroyed, giving observers an inaccurate view of its true nature. 

Sort of like great white sharks, the barreleye likes to hunt from below. However, unlike the great white, the barreleye remains motionless, peering upward, looking for silhouettes darkening the light that’s struggling to reach the 2,000-foot depths. 

This clear barreleye has been observed to prey on small fish and jellyfish. They’re also thought to steal food from siphonophores, a group of cnidarians. 

Barreleye Major Fact: Dome Is Where the Eyes Are

So most fish have eyes on the sides of their head. They also tend to be on the outside of their bodies. But Mackenmike doesn’t care about ocular conventions.

I asked you to specifically avoid talking about the eyes in the description because things are going to get wild here.

Mackenmike’s classic transparent head has two prominent objects inside. They are largeish bright green orbs nestled in a sort of short eye-stalk. Mackenmike’s eyes kinda look like that giant ball at Magic Kingdom that spins around on the water.

They also look like sci-fi planetary maps or alien incubation pods.

Here’s the rub: they’re located where the brain would normally be and they’re facing directly upward. Most barreleye fish have eyes that look like weird tubes and face upward, but they’re still on the outside of the body.

Since the head is almost completely transparent, it can look straight through its own head to look for prey above it. It spends most of its time completely motionless, waiting for something to swim overhead.

But if its eyes are facing up through its head, how does it know where it’s going when it spies some prey?

Locked into Kill-Mode

Well, its eyes usually face upward, but they can also face forward. If you look at a picture of this Pokémon, you’ll see what looks like eyes on the front of its face—you know, where they’re supposed to be. But those are just soulless holes for the eyes to pop into – as far as we know.

The eyes that are normally locked upward can rotate forward like binoculars and pop into those holes so that it can look forward while it swims toward prey.

Scientists think that the green in their eyes helps filter out any sunlight that may reach them so that they can focus on the bioluminescent jellies that make up their diet. Pictures make it look like mackenmike is bioluminescent but that’s just the underwater ROV’s headlights passing through the head.

We’ve only recently discovered both the transparent head and the rotating eyes because any barreleye that was brought to the surface would look very different without the water pressure they’re used to – kinda like blobfish.

Ending: So take a moment to sit still, level out, and keep looking up like the barreleye fish here in LDT


Thank you to Casy for creating our theme song. To hear more of Casy’s music search Casy Michelle on Youtube

Thank you to Brian for creating the episode art. See more of Brian’s art at xNamaru on Instagram or Twitter