The Blotched upside-down catfish, Synodontis nigriventris, is a species of upside-down catfish native to the Congo Basin of Cameroon, the Democratic Republic of the Congo and the Republic of the Congo.
Appearance and anatomy
Blotched upside-down catfish are small, reaching a maximum of 9.6 centimetres (3.8 in) SL. Like other members of the family Mochikidae, they have large eyes, a large dorsal fin and three pair of barbels. These fish are adapted to spend most of their time upside-down. This is reflected in the fish's pigmentation – their bellies are darker than their backs, a form of countershading. These fish have lighter colors on the top of their bodies and darker colors below used for camouflage. The lighter colors on the top of them make it harder for predators to see the fish when looking up toward the sky but only when the fish are swimming upside-down.
The catfish swims and rests upside down in the water. These fish were more likely to swim faster when they were upside down and they were more likely to be upside down around another object or at the water bottom. The more objects around the fish, the more the fish will swim upside down. When it is close to any object, it usually puts its ventral side closest to the object. It will swim upside down more often when it is at the bottom of the water. Synodontis nigriventris rarely swim in the middle of the water and instead either swim at the bottom or top of the surface.
It is unclear why Synodontis nigriventris swims upside down since the inner ear seems to be like any ear of any other fish. There are no special features that explain why it swims upside down and so it is just like every other fish when it comes to the inner ear. If the fish tilts its body or its eyesight changes, this can affect the way in which the fish swims. Synodontis nigriventris swims upside down when it eats. It is believed that by swimming upside down this somehow helps them catch prey at the surface.
In the aquarium
The blotched upside-down catfish is well suited to aquariums because of its small size (typically 9 or 10 cm or less) and peaceful demeanor. They should be kept in schools of 3 minimum for best effect. They should be fed a variety of good quality flake food, tablet food, frozen bloodworm and live food as daphnia. Provide caves or ledges for them to loaf in.
- Froese, Rainer, and Daniel Pauly, eds. (2011). "Synodontis nigriventris" in FishBase. December 2011 version.
- Axelrod, Herbert R. (1996). Exotic Tropical Fishes. T.F.H. Publications. ISBN 0-87666-543-1.
- Ken Ohnishi, Akihisha Takahashi, Hiroaki Tanaka & Takeo Ohnishi (1996). "Relationship between frequency of upside-down posture and space size around upside-down catfish, Synodontis nigriventris". Biological Sciences in Space 10 (4): 247–251. doi:10.2187/bss.10.247. PMID 11540345.
- Sanford, Gina (1999). Aquarium Owner's Guide. New York: DK Publishing. ISBN 0-7894-4614-6.
- D. L. Meyer, C. Platt & H.-J. Distel (1976). "Postural control mechanisms in the upside-down catfish (Synodontis nigriventris)". Journal of Comparative Physiology 110 (3): 323–331. doi:10.1007/BF00659148.
- Robert W. Blake & Keith H. S. Chan (2007). "Swimming in the upside down catfish Synodontis nigriventris: it matters which way is up". Journal of Experimental Biology 210 (17): 2979–2989. doi:10.1242/jeb.006437. http://jeb.biologists.org/content/210/17/2979.abstract.