Mystery of Coelacanth Fish Solved: Here's Why Ancient Creature Swims Upside Down

Scientists now better understand one of the rarest fish in the world. They uncovered the coelacanth's physiology using CT and MRI scanners and discovered something unexpected. The uncommonly threatened deep-sea fish is built to swim upside down and attack its prey.

According to Oceana, the coelacanth is a rare marine fish representing a live branch of a long-extinct lineage of once-common fishes. These animals may cruise vertically with their heads directed toward the ocean floor while they search for food, which is generally cephalopods and tiny fish since they have a lot of bone in their heads and tails and few vertebrae.

Additionally, they lack a swim bladder. The fish usually inhabit caverns that are 600 hundred feet or deeper. Since they don't have a swim bladder, they are less buoyant and don't have to work as hard to maintain their depth.

Researchers published their study, "Buoyancy and hydrostatic balance in a West Indian Ocean coelacanth Latimeria chalumnae," in BMC Biology.

Mystery of Head Turning Fish Resolved

Its anatomy is well known since so many coelacanth specimens have been dissected. But nothing is understood about the physiology-or how the fish works. Researchers have just learned about this incredibly secretive and unusual deep-sea creature.

"We discovered that the coelacanth has a special skeleton with a lot of bone mass in the head and tail, while there are almost no vertebrae," said study co-author Peter Rask Møller in a statement.

Møller, who is an associate professor and curator at the University of Copenhagen's Natural History Museum of Denmark, mentioned: "The heaviest parts are at either end of the fish, which makes it easy for the fish to stand itself on its head."

According to Møller, a helpful mechanism for the fish's way of existence is the balance point.

Møller is the only person to ever do the study on the Danish specimen, which has been maintained entire and has only ever been displayed, along with Henrik Lauridsen of Aarhus University and a group of researchers.

Researchers at Aarhus University Hospital in Skejby could more accurately mimic the species without harming it by placing the fish in CT and MRI scanners.

Secret to Swimming Upside Down

The models accurately depict the body's fat and bone mineral distribution, Phys.org wrote. The models, among other things, aid in the explanation of the coelacanth's distinctive "headstand drift hunting" method, which involves gently drifting down the seabed with its head and nose downwards while using an electrosensitive organ to examine the bottom for cephalopods and fish to feed.

The researchers also identified the amount of fatty tissue in the fish's fatty bladder. Since coelacanths don't have a typical gas swim bladder as modern fish have, they have a precise distribution of fatty tissue throughout their bodies.

The data demonstrate a relationship between fish fat content and the depths at which they can survive, where fat enables the fish to stay neutrally buoyant and require little energy to persist hundreds of meters below the surface.

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