The name upside-down catfish is most commonly used by aquarists to refer to the mochokid

catfish Catfish (or catfishes; order (biology), order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Catfish are common name, named for their prominent barbel (anatomy), barbels, which resemble a cat's whiskers, though not ...

'' Synodontis nigriventris'' alternately known to

ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 35,800 species of fish had been described as of March 2 ...

s as the blotched upside-down catfish or false upside-down catfish. However, a number of other fish may also be known by this name: *'' Mystus leucophasis'' – Asian upside-down catfish *'' Synodontis angelicus'' – spotted upside-down catfish *'' Synodontis aterrima'' – sometimes sold as ''S. nigriventris'' in the aquarium trade, but in the past not identified as a separate species by

retail Retail is the sale of goods and services to consumers, in contrast to wholesaling, which is the sale to business or institutional customers. A retailer purchases goods in large quantities from manufacturers, directly or through a wholes ...

ers *'' Synodontis batensoda''- '' Brachysynodontis batensoda'' – known as giant upside-down catfish, or squeaker. Found in northern, northeast, and western Africa *'' Synodontis contracta'' – big-nosed upside-down catfish, sometimes sold as ''S. nigriventris'' to aquarists, a species with which it is easily confused *'' Synodontis nigrita'' – false upside-down catfish, very commonly sold as ''S. nigriventris'' in the aquarium trade and only recognised as a different species once the fish matures (adults are more than twice the size of adult ''S. nigriventris'') *'' Synodontis nigriventris''- blotched upside-down catfish,these fish are adapted to spend most of their time upside-down. The name 'dwarf upside-down catfish' is also used for small (around 10 cm) species of the catfish genus ''

Synodontis ''Synodontis'' is the largest genus of mochokid catfishes. It is the biggest genus within the 10 genera and 190 different species in the family Mochokidae. ''Synodontis'' has over 131 different species within the genus. ''Synodontis'' are also k ...

''. In the aquarium trade, the name is almost always applied to ''S. nigriventris'' or species with which it may be confused, such as ''S. aterrima'', ''S. contracta'', and juvenile ''S. nigrita'' (adults of which are around 20 cm so are not "dwarf" species at all). As its common name implies, the upside-down catfish will swim upside-down. One theory accounts for this unusual behavior as a feeding strategy. In the wild, it often grazes on the undersides of submerged branches and logs, and swimming upside-down makes these areas more accessible. A different theory suggests swimming upside-down makes aquatic surface respiration more efficient.

References

{{Animal common name Fish common names Bagridae Mochokidae