Synodontis Cuvier, 1816 (Teleostei, Mochokidae) species are often extremely abundant in local fisheries catches over their entire distribution range. They are appreciated as food as well as popular aquarium fishes. However, some species are extremely difficult to identify due to the taxonomically unreliable nature of prominent morphological features. Establishing the correct identification is important and can have far-reaching consequences (e.g. in fisheries, conservation, stock assessment, and angling records may be compromised by misidentifying species due to the complicated nature of present identification keys). The systematic status of many southern African Synodontis species is poorly understood and their identification remains problematic. This study involves characterising the species of the genus Synodontis by comparative morphological and genetic studies due to the above-mentioned problems. Extensive field studies have lead to a simplified identification key. This key excludes the detail character information included in the published key that masks the more reliable characteristics. Synodontis njassae, S. macrostigma, S. macrostoma, S. leopardinus, S. thamalakanensis, S. woosnami, S. vanderwaali, S. nigromaculatus and S. zambezensis were used in an allozyme study with Parauchenoglanis ngamensis as outgroup. Fixed allele mobility differences were obtained at eight of the 15 loci studied. The dendrograms grouped all species with convex humeral processes in one clade. The species with concave humeral processes also grouped together, but with poor resolution with DNA - sequence analysis. A biochemical genetic study of laboratory produced hybrids between two species of Synodontis was done to provide additional information on the species boundaries and to determine whether genetic markers can be found to identify them. Hybrizymes were found in the latter study. Such markers are of conservation importance due to the uncontrolled translocation of many exotic fish species. This is the first study to evaluate the phylogenetic relationships of southern African Synodontis species and of hybrids, and the simplified identification key will be useful for positive identification of the species studied. / Prof. F.H. Van der Bank
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:10629 |
| Date | 11 September 2008 |
| Creators | Bruwer, Erna Elfriede |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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