On any given day, a fish swimming or floating upside down is very, very ominous. The most obvious conclusion is that the little guy is either terribly sick, or worse, RIP. But this is not the case with some special species of fishes, who have made it their life’s purpose to master the art of swimming upside down. The most common flip swimmer is the catfish, and, if hypotheses and theories are to be believed, it has changed its swimming alignment for a reason. Let’s try to understand more about upside down catfish.
Usually, when someone refers to an upside-down catfish, they’re talking about the mochokidae catfish, known to Science as Synodontis Nigriventrism. However, there are some other special catfish species that can flip over and swim. The Mochokodae catfish, though, swim inverted, with their ventral side towards the water. Many have hypothesized that this fish has a high ability to stay in an upside-down position, and this posture might only be possible due to its hypothesized specific gravity information processing system.
Whatever the anatomy may be, the reasons don’t seem far-fetched at all. It seems that the upside down swimming helps them absorb the surface oxygen better, especially when it comes to low-oxygen water areas due to chemically induced hypoxia. The position saves the catfish a lot of energy as compared to the regular fish who have to keep turning over to access water’s oxygen. The flip position also seems to help catfish have access to food that other fish in the water don’t eat, or better, can’t eat, because of their ‘normal’ positioning.
Because of evolution, the upside down swimming has affected the appearance of the these fish. While fish are usually darker on the top and lighter on the bottom, upside down catfish are the exact opposite. This ‘camouflaging’ has come in handy, because flip swimmers are easy food, being only a few inches long, but their appearance has helped them avoid predators, not only because of their color, but also because the posture allows them to look under the water better. Upside down swimming has also helped them catch prey like insects and larvae easily.
So next time, when you see a catfish floating upside down in an aquarium, think twice before breaking the ‘bad news’!