Did you know that there’s a particular type of creepy fish that has an invisible head?
In this post, you’ll learn all about it in our top 10 list with Barreleye fish facts.
1. They have an alternative name
Barreleye fish are a small type of deep-ocean fish and a member of the family Opisthoproctidae in the order Argentiniformes. There aren’t a huge number of members in this order because they have only been distinct from their previous order, the Osmeriformes, recently.
They do have an easier name as they are mainly referred to as “spook fish.”
2. There are 3 different types of barreleye fish
The Argentiniformes are an order of ray-finned fish which consists of about 6 to 7 families, nearly 60 genera, and at least 228 different species.
There are basically 3 different types of barreleye fish based on their morphology:
Genera Opisthoproctus and Macropinna – Stout, deep-bodied barreleyes.
Genera Dolichopteryx and Bathylychnops – Slender and elongated barreleyes.
Genera Rhynchohyalus and Winteria – The type in between the stocky and slender barreleyes.
3. They have really distinctive eyes
Even though the body type of these species can vary significantly, the one thing these creatures have in common is their distinctive eyes. Their tubular eyes have the option to both look straight upwards similar to the eyes of the stargazer, as well as straight ahead.
It’s only since 2009 that researchers discovered that they have the ability to look straight ahead as well because since this particular species was described for the first time in 1939, it was always assumed that they were only able to see what’s directly above them.
This means that these fish not just have tunnel vision but can actually see pretty much everything around them!
4. Barreleye fish has a transparent, dome-shaped head
Barreleyes live in the depths of the ocean at a depth of between 600 to 800 meters (2,000 to 2,600 feet). There’s hardly any light here so their eyes have really adapted to the conditions.
One of the most astounding barreleye fish facts is that they appear to have a transparent, fluid-filled shield that resembles a transparent dome on top of their head. This headgear appears to be protecting their tubular eyes.
Another reason can be the very opposite as this shield might be allowing them to absorb as much light as possible.
This is really an astounding feature that can only be noticed at the bottom of the ocean because whenever barreleyes are hauled up from the depths of the ocean, the shield gets destroyed. When this happens, they turn into the same gooey mess as the famous blobfish because of the rapid change in pressure!
These creatures live in just about all parts of the tropical-to-temperate waters of the Atlantic, Pacific, and Indian Oceans. This means they have a huge range and are far from extinct.
They also have a very large range in terms of depth as they live anywhere between 400 and 2,500 meters (1,300 to 8,200 feet) deep.
Another one of those remarkable barreleye fish facts is that it seems their vertical range is determined by the temperature of the water. The isotherm for 8 °C (46 °F) is 400 meters and you won’t find them above this level, something that is consistent wherever they live.
6. Barreleye fish can produce light as well
Just about all of the barreleye species have organs that can produce light, which helps them to spot prey in the dark depths of the ocean. Some species have these types or organs all across their belly, some just have one such organ.
This isn’t anything near the light of a flashlight though as they also have to stay safe from predators themselves. At best, this is a very weak glowing light that allows them to absorb just enough light to see what they are eating.
7. They have small, spineless fins, except for 2 large ones
All barreleyes have very small and spineless fins. Some species, however, have large pectoral fins which they use to navigate in the ocean. This is mainly because they don’t have a gas bladder which is used by most bony fish to control their movements.
Opisthoproctus grimaldii / Wiki Commons
8. They pretty much stay in the same place their entire life
It’s not as if they really need their fins to move around as they pretty much just float around in the ocean. They avoid predators using their light organs so they pretty much remain invisible, so swimming away from attacks isn’t needed.
They also don’t care about diel vertical migrations, which means they pretty much float around and see how it goes.
9. They follow a huge sea monster to eat
The only time they put in some effort is to swim around siphonophores, also known as colonial jellies. These jellyfish can grow up to 10 meters (33 feet) in length and pretty much operate as huge living fishing nets, dragging thousands of stinging tentacles with them to catch food.
Barreleyes are known to simply follow the huge jellyfish and scoop up whatever they leave behind such as small zooplankton like hydroids, copepods, and all sorts of small crustaceans.
They use their remarkable eyes to avoid the deadly sting of the siphonophore’s tentacles.
10. They remain solitary their entire life as well
Very little is known about the reproduction cycle of the barreleyes, but it appears that they remain solitary their entire lives. No social contact, just floating around in the vast depths of the ocean.
It’s assumed that they are simply pelagic spawners, which means that as much sperm and eggs are released in the ocean with the hopes of the eggs being fertilized.
That’s the life of the barreleye fish! Extremely dark and extremely lonely, and most importantly, extremely fascinating because of their extremely peculiar transparent head!
