Upside-down catfish

The name upside-down catfish is most commonly used by aquarists to refer to the mochokid catfish Synodontis nigriventris alternately known to ichthyologists as the blotched upsidedown catfish.^[1] However, a number of other fishes may also be known by this name:

• Brachysynodontis batensoda - Giant upside-down catfish.^[2]
• Mystus leucophasis - Asian upside-down catfish.^[3]
• Synodontis angelicus - spotted upside-down catfish.^[4]
• Synodontis aterrima - Sometimes sold as Synodontis nigriventris in the aquarium trade but not identified as a separate species by retailers.^[5]
• Synodontis contracta - Big-nosed upside-down catfish, sometimes sold as Synodontis nigriventris to aquarists, a species with which it is easily confused.^[6]
• Synodontis nigrita - False upside-down catfish, very commonly sold as Synodontis 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 Synodontis nigriventris).^[7]

The name dwarf upside-down catfish is also used for small (around 10 cm) species of the catfish genus Synodontis. In the aquarium trade, the name is almost always applied to Synodontis nigriventris or species with which it may be confused, such as Synodontis aterrima, Synodontis contracta, and juvenile Synodontis nigrita (adults of which are around 20 cm so are not "dwarf" species at all).^[5][6][7].

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 underside of submerged branches and logs, and swimming upside down makes these areas more accessible.^[8]

References