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.[1] Synodontis has over 131 different species within the genus.[2] Synodontis are also known as squeakers, due to their ability to make stridulatory sounds through their pectoral fin spines when handled or disturbed.[3] Synodontis make a sound that sounds like squeaking by rubbing their spines together. They do this when they have been frightened or when they become angry.[2] Synodontis may also squeak when they are taken out of the water.[1] These catfish are small- to medium-sized fish[4] with many species exhibiting attractive spotted markings. Some species are also known for naturally swimming belly-up, earning the name upside-down catfish.[3] Some of these species are Synodontis contractus and Synodontis nigriventris. While some of these species are known to swim upside down, another species, Synodontis multipunctatus, is a brood parasitic cuckoo catfish.[1]

Synodontis
Temporal range: Early Miocene–Recent
Synodontis njassae
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Siluriformes
Family: Mochokidae
Genus: Synodontis
G. Cuvier, 1816
Type species
Silurus clarias
Synonyms
  • Leiosynodontis Bleeker, 1862
  • Pseudosynodontis Bleeker, 1862

Distribution
Synodontis petricola

Synodontis is a freshwater catfish that is most commonly found throughout Africa, occurring mostly in Central and West Africa.[1] Synodontis is the most widely distributed mochokidae genus, occurring throughout most of the freshwaters of sub-Saharan Africa and the Nile River system.[3] They can live in freshwaters which can be creeks, ponds, streams, lakes, and rivers.[2] Their distribution is similar to that of cichlid fishes, however, unlike cichlids the majority of their diversity occurs in rivers not lakes.

Evolutionary history

Synodontis catfish form a small endemic radiation in Lake Tanganyika,[1][5][6] which includes the non-endemic species S. victoriae. This radiation is thought to have evolved relatively recently (~5.5. Million years ago), having diversified within full lacustrine conditions.[5][6] This is also the case for other endemic Lake Tanganyika lineages such as mastacembelid eels[7] and platythelphusid crabs for example.[8] Lake Tanganyikan Synodontis have also been shown to be Müllerian mimics,[9] and that at least one species (Synodontis multipunctatus) is a brood parasite.[10]

Fossil record

The earliest fossils of Synodontis in East African are from the Early Miocene. Many Synodontis fossils are the spines because they are very sturdy and so they are preserved better. The fossils of spines that are found are used to determine the family or genera of the fish but it cannot determine the species. Synodontis species that have survived and are still living can be identified by the shape of their whisker like organs on their heads called barbels, which relate to touch. The can also be identified by the color of their skin, the skull bones, and the number and length of the teeth.[11]

Ecology

Synodontis species are omnivorous generalists, feeding on a wide spectrum of different foods and are largely unspecialized. Insects, crustaceans, mollusks, annelids, seeds, and algae have been found in the stomachs of different species of Synodontis.[2] They are bottom-feeders and may be detritivores, some species may also be able to adapt to filter feeding.[4] This allows them to cope with seasonal and habitat changes and gives them a better ability to colonize different habitats.[1] Different Synodontis species have somewhat different growth rates but most of them are fairly similar. Females of a species are generally larger than the males. There is a great increase in growth the first year in both male and female and then the growth slows down as they become older.[12] The form and structure of these fish are very different compared to other fish. The size and shape of the mouth are distinct because of its ventral mouth and these fish usually are triangular or cylindrical when looking at it from the side.[2] Not much is known about the reproduction in these fish. It has been determined that July to October is when they spawn and that they swim in pairs during this spawning time.[2] Species of Synodontis have been noted to reproduce with the flooding period of the rainy season.[4]

Relationship to humans
Synodontis nigriventris is a popular aquarium fish.

Many Synodontis species are prized ornamental fish in the fishkeeping hobby.[3] While some of the Synodontis species are prized because of their color or behavior, other species are wanted for food. Some of the bigger species in the genus are important food sources for the people in Africa.[1]

Species

There are currently 131 recognized species in this genus:[13] Synodontis accounts for about one-quarter of African catfish species.[1] This genus has more members than any other African teleost genus other than Barbus and Haplochromis.[4]

Newer species are listed with references.

References
  1. Stephan Koblmüller; Christian Sturmbauer; Erik Verheyen; Axel Meyer & Walter Salzburger (2006). "Mitochondrial phylogeny and phylogeography of East African squeaker catfishes (Siluriformes: Synodontis)". BMC Evolutionary Biology. 6: 49. doi:10.1186/1471-2148-6-49. PMC 1543664. PMID 16784525.
  2. John P. Friel & Thomas R. Vigliotta (March 2, 2009). "Mochokidae Jordan 1923: African squeaker and suckermouth catfishes". Tree of Life Web Project. Retrieved December 4, 2012.
  3. Friel, John P.; Vigliotta, Thomas R. (2006). "Synodontis acanthoperca, a new species from the Ogôoué River system, Gabon with comments on spiny ornamentation and sexual dimorphism in mochokid catfishes (Siluriformes: Mochokidae)" (PDF). Zootaxa. 1125: 45–56.
  4. Lalèyè, Philippe; Chikou, Antoine; Gnohossou, Pierre; Vandewalle, Pierre; Philippart, Jean Claude; Teugels, Guy (2006). "Studies on the biology of two species of catfish Synodontis schall and Synodontis nigrita (Ostariophysi : Mochokidae) from the Ouémé River, Bénin" (PDF). Belgian Journal of Zoology. 136 (2): 193–201. Archived from the original (PDF) on 2009-12-29.
  5. Julia J. Day & Mark Wilkinson (2006). "On the origin of the Synodontis catfish species flock from Lake Tanganyika" (PDF). Biology Letters. 2 (4): 548–552. doi:10.1098/rsbl.2006.0532. PMC 1833983. PMID 17148285.
  6. J. J. Day; R. Bills & J. P. Friel (2009). "Lacustrine radiations in African Synodontis catfish". Journal of Evolutionary Biology. 22 (4): 805–817. doi:10.1111/j.1420-9101.2009.01691.x.
  7. Brown KJ, Rüber L, Bills R, Day JJ (2010). "Mastacembelid eels support Lake Tanganyika as an evolutionary hotspot of diversification". BMC Evolutionary Biology. 10: 188. doi:10.1186/1471-2148-10-188. PMC 2903574. PMID 20565906.
  8. Marijnissen SA, Michel E, Daniels SR, Erpenbeck D, Menken SB, Schram FR (August 2006). "Molecular evidence for recent divergence of Lake Tanganyika endemic crabs (Decapoda: Platythelphusidae)". Molecular Phylogenetics and Evolution. 40 (2): 628–34. doi:10.1016/j.ympev.2006.03.025. PMID 16647274.
  9. Wright JJ (February 2011). "Conservative coevolution of Müllerian mimicry in a group of rift lake catfish". Evolution; International Journal of Organic Evolution. 65 (2): 395–407. doi:10.1111/j.1558-5646.2010.01149.x. PMID 20964683.
  10. Sato T (1986). "A brood parasitic catfish of mouthbrooding cichlid fishes in Lake Tanganyika". Nature. 323 (6083): 58–9. doi:10.1038/323058a0. PMID 3748180.
  11. Pinton A, Fara E, Otero O (January 2006). "Spine anatomy reveals the diversity of catfish through time: a case study of Synodontis (Siluriformes)". Die Naturwissenschaften. 93 (1): 22–6. doi:10.1007/s00114-005-0051-4. PMID 16261332.
  12. H. M. Bishai & Y. B. Abu Gideiri (1965). "Studies on the biology of genus Synodontis at Khartoum". Hydrobiologia. 26 (1–2): 85–97. doi:10.1007/BF00142257.
  13. Froese, Rainer and Pauly, Daniel, eds. (2014). Species of Synodontis in FishBase. June 2014 version.
  14. Jeremy J. Wright & Lawrence M. Page (2006). "Taxonomic revision of Lake Tanganyikan Synodontis (Siluriformes: Mochokidae)" (PDF). Bulletin of the Florida Museum of Natural History. 46 (4): 99–154.
  15. Jeremy J. Wright & Lawrence M. Page (2008). "A new species of Synodontis (Siluriformes: Mochokidae) from tributaries of the Kasai River in northern Angola". Copeia. 2008 (2): 294–300. doi:10.1643/CI-07-040.
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