The black-spotted yellow fish shaped like the square box you are seeing has the scientific name Ostracion cubicus, commonly known as the round-backed puffer or the golden box puffer. They are concentrated in the coral reefs of the Pacific, Indian Ocean and the southeastern Atlantic Ocean, feeding mainly on small prey (smallworms, crustaceans, mollusks and small fish…) and fragments. organic debris on the surface of the reef.
The body color is bright yellow, there are round black spots all over the body, the whole fish is like a box with black spots on a yellow background. Since the golden chest puffer likes to live alone and is very shy, this dark spot and bright yellow skin serves as a warning to potential predators outside.
When attacked or threatened, the skin of the golden chestnut puffer fish releases a characteristic neurotoxin Ostracitoxin. Many people have tried to keep it without success, the reason is that if kept in a relatively closed area, such as an aquarium, the toxins released can kill other fish in the tank.
Skeleton diagram of the long-tailed horned puffer fish
Most fish have soft, elongated bodies that are adapted to the water environment, allowing them to swim freely. However, the body of the golden chest puffer fish has a hard box-shaped skeleton, very different from the fish we commonly know, even making one wonder if there is something wrong with its evolution. they? How can they swim with this boxy body?
However, what no one expected is that although it looks slow, the golden chest puffer is extremely agile, almost one of the fastest fish in the reef area.
In 2002, a team of researchers used 3D printed models of puffer fish to study how water circulates around their bodies. They found that when the current hits the puffer fish, small eddies form near their exoskeleton, helping to stabilize the movement.
This ingenious survival technique is important for reducing disturbance of the water flow and maintaining stability in fast-moving waters. Finally, humans have found an explanation for the evolution into this strange shape of the puffer fish in general and the golden box puffer in particular.
If you look closely, you can see its tail sticking to its body
However, the researchers seem to have overlooked one detail: If the eddy currents around the golden chest puffer’s skeleton can give them directional stability, the fish can also be said to be dependent into the vortex around their body. So is it too difficult for them to move in the other direction when the predator suddenly attacks?
Moreover, according to the observation of research staff, the golden chest puffer fish is very flexible, when in danger, it will quickly turn around and swim into the reef to escape.
Research by S. Van Wassenbergh et al. in 2015 challenged the earlier theory of whirlpools, arguing that the influence of these eddies is canceled out by the moment of force generated in front of the box-shaped skeleton. of the puffer fish and they cannot swim in a stable position. On the contrary, they are very easy to “turn over”.
The reason the golden chest puffer is so flexible is because they use their dorsal, pectoral and caudal fins to turn quickly to help their bodies maintain a stable posture in flowing water, similar to how helicopters maintain. stability in the air thanks to the raised propeller and the vertical propeller at the tail. When it comes to a quick turn, the puffer fish just needs to bend the caudal fin to the side and their body will turn over, making a sharp turn in a very small space.
That is to say, the golden chest puffer’s agility is shaped by a combination of the aerodynamically unstable body and the way the fins move. Moreover, they do not need to swim long distances, and have venom and “armor”. Therefore, giving up speed and opting for agility is a long-term evolutionary choice.
Seeing that, some people may ask, how does this fish normally swim with a boxy body? If you’ve ever watched fish move, you’ll see that they all move in the same way, the regular movement of the tail, body, and coordination of the fins.
The pectoral and pelvic fins can maintain the balance of the fish in the water, unlike other types of fins, the pectoral fins are not vertical but horizontal, so the pectoral fins will shake water up and down during movement to help the fish. self control up and down. The dorsal and caudal fins hold the fish upright in the water, much like the keel (the longitudinal section connecting the hull and the stakes in the center of the hull) at the bottom of a sailboat.
The tail fin can not only provide more power for the fish to swim, but also help the fish change the direction of swimming. When the caudal fin swings to the left, the fish moves to the left, when the caudal fin swings to the right, the fish moves to the right.
However, due to differences in habitat and behavior, the function and shape of the fins also underwent corresponding changes during long-term evolution.
Source: The Paper