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A fish with a transparent head. That sounds something straight out of science fiction, but it is everything but science fiction. A fish like that actually exists and lurks in the depths of the Pacific Ocean.

Known as the Barreleye Fish, it is a true miracle of Nature. You won’t believe until you actually see it. So, without further ado, let us delve deep into the information about this ‘unbelievable’ creature. We are pretty sure you are going to love these Barreleye Fish facts.

Before we start…

Scientific NameMacropinna microstoma

Barreleye Fish Facts: 1-5 | Discovery

1. Chapman – a marine biologist – was the first person who discovered the Barreleye Fish back in 1939. Unfortunately however, till 2004 no one knew that it had a transparent head.

2. When the fish was being dragged up after being caught on nets, the transparent portion of the head was destroyed simply because it was too fragile.

3. The first ever photograph of the fish showing its transparent head was taken in 2004.

4. Later when technology evolved, scientists were capable of not only capturing the fish in its natural environment but also managed to capture a few specimen.

5. Reisenbichler and Robinson were the two researchers from Monterey Bay Aquarium Research Institute who studied the fish in its natural environment and captured one specimen and studied it in an aquarium.

Barreleye Fish Facts: 6-10 | Description – Head and Eyes

6. The Barreleye Fish has one of the most unusual appearance among deep sea creatures. The first thing that one notices is its dome-shaped head that is transparent on the top.

7. Inside the dome (which is actually filled with clear fluid) are its two barrel-shaped or tubular eyes that are embedded inside the head. They remain pointed upward. It was previously believed that the eyes were fixed in that position.

8. Closer examination of the fish revealed that its eyes can actually rotate inside the transparent dome-shaped head, allowing them to look straight ahead and not just upward.

9. These tubular eyes of the fish are known to be ultra sensitive and have a green fluid that is capable of capturing the tiniest bit of light at the great depths at which it lives. It is believed that the fish can filter out whatever sunlight gets through and allow the fish to bioluminescent light emitted by jellies and other sea creatures.

10. The eyes stay pointed upward when the fish looks for food. The eyes point forward when the fish feeds.

Barreleye Fish Facts: 11-15 | Mouth, Nostrils, Adaptations

11. The mouth of the Barreleye Fish is very small, suggesting that it is very picky when it comes to the prey. The small mouth won’t allow the fish to eat big prey.

12. The small mouth is a pointed snout. There are no teeth present in the mouth. The body of the fish is dark brown in color with large silvery fins.

13. Right above its mouth are two small eye-like spots. However, they aren’t the eyes. They are actually olfactory organs of the fish. If we try to draw and analogy, those are similar to human nostrils.

14. One of the most incredible adaptations of the Barreleye Fish is that they have large and flat fins. These fins allow the fish to stay absolutely motionless in deep waters.

15. While the fins allow it to stay absolutely motionless, the fins are also designed to give them the ability of precise maneuvers which hunting for food.

Barreleye Fish Facts: 16-20 | Hunting

16. Barreleye Fish are ambush predators. They stay motionless in water at great depths and look upward. Their specially designed eyes give them a binocular vision.

17. First, their specially designed eyes allow them to clearly distinguish between ambient light and bioluminescent light. This is possible because of the high number of rod cells that they have in their eyes.

18. Second, when the prey is located high up, the fish uses its binocular vision to narrow in on the prey using precise maneuvers with aid of its fins. It moves up vertically to reach its prey.

19. It is believed that the Barreleye Fish is actually steals food from siphonopores. Scientists believe that small creatures that are trapped in the stingy tentacles of the siphonopores are spotted by Barreleye Fish and then using its precise maneuvers, the fish steals the food from the siphonopores.

20. What about the sting that the tentacles of the siphonopores can gives? Scientists say that the fluid-filled transparent head protects the eyes of the Barreleye Fish from those stings and the fins allow the fish to maneuver between the tentacles of the siphonopores.

Barreleye Fish Facts: 21-25 | Diet, Behavior, Reproduction

21. What does the Barreleye Fish eat? Scientists have actually examined the stomachs of this fish and found remains of cnidarian animals (a phylum with over 10,000 animal species) and jellyfish.

22. Upon closely studying the fish’s visceral anatomy, scientists have come to a conclusion that the diet of the Barreleye Fish is quite broad including zooplankton that include both gelatinous and crustacean variants, tentacles and nematocysts of siphonopores, small fish etc.

23. Coming to the behavior of Barreleye Fish, these are solitary creatures. They are not social and will stay still and motionless with eyes looking upward, scanning prey.

24. Coming to the reproductive behavior, Barreleye Fish are thought be pelagic spawners. This means that females will lay eggs in water and males will release sperms in water.

25. The eggs get fertilized in the water. The fertilized eggs are planktonic in nature and they are buoyant in nature. They will float around in shallow depths and drift with currents. As they grow into adults, they will gradually move at greater depths.

Barreleye Fish Facts: 26-30 | Predators, Habitat, Size

26. Scientists are yet to find whether they have any predators or not. However, as the rule of thumb goes, every living creature has a predator and hence, it is expected that even Barreleye Fish has predators. It is only a matter of time before scientists find out.

27. Barreleye Fish is a deep water fish. It is usually found at a depth of 2,000 feet to 2,600 feet but they can also be found at depths of 3,330 feet.

28. This fish is found in the three major oceans of the world – the Pacific Ocean, the Atlantic Ocean and the Indian Ocean.

29. Barreleye Fish is not very big. The average size is around 15 centimeters (6 inches), the species can grow up to 44 centimeters or (~17.3 inches).

30. Barreleye Fish Fun Fact: The fish lacks lateral vision. That is, it cannot see sideways. It can see upward and forward. This happens because of the way the eyes are fixed allowing only a forward and upward swivel movement. And yes, the fish lacks cone cells.

Image Credit: Public Domain

Sources:1, 2, 3, 4

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