The Topsy-turvy Upside-down Catfish

Habitat: Congo Basin of Cameroon, the Democratic Republic of the Congo and the Republic of the Congo

This odd fish is quite the confused specimen. It’s called the Upside-down Catfish (Synodontis nigriventris) and as the name implies… it actually swims upside down! They’re small fish, reaching a maximum of 9.6 centimetres (3.8 in). And yes, they are actually adapted to swimming upside down as their pigmentation suggests. Their bellies are darker than their backs, which is a form of countershading. That means that fish looking up from the bottom will “see” the catfish as blending in with the lighter sky while fish looking down on the catfish from above will “see” the catfish as part of the darker river bottom; either way making it very hard to spot. 

We’re not entirely sure why the Upside-down Catfish swims upside down but the most popular theory is that it’s a feeding strategy. In the wild, it often grazes on the underside of submerged branches and logs, and swimming upside down makes these areas more accessible. Either that or it’s perpetually had a bit too much to drink and can’t swim straight. Who knows!