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

The presented thesis consists of three papers/manuscripts (one published, one under review, one manuscript) on population genetic aspects of a host-parasite model, caryophyllidean tapeworm Wenyonia virilis and mochokid catfish Synodontis schall, in recently separated drainage basins, Lake Turkana and the Nile River. Three main topics are addressed herein: (i) intra- and inter-population genetic variability in and among hosts and parasites, (ii) comprehensive assessment of host model taxonomic status using multiple approaches, (iii) comparison of parasite intraspecific phenotypic with population genetic pattern. Two different genetic markers were applied to address these topics mtDNA (coxI) and whole genome scanning method (AFLP).

The alpha taxonomy of the southern African Synodontis is reviewed, based on the analysis of 48 characters. The previously descriptive characters of barbel branching and humeral process shape are compared by various quantitative methods. The variation in colour pattern is recorded with the aid of detailed line drawings. The definitions of head length, head width and humeral process length are altered slightly from their traditional descriptions to ensure greater consistency and precision in measurement. New characters include the size of the caudal fork, the number, shape and arrangement of the premaxillary teeth, and two measurements between the cranium and pectoral girdle. Both uni- and bivariate methods are used to record and compare the intraspecific variation of each character. Principal components analysis of 19 morphometric characters is used to assess the degree of similarity of nine allopatric populations of S. zambezensis. Ten species are recognized from the study area, two of which are described as new: S. nebulosus Peters 1852, S. zambezensis Peters 1852, S. nigromaculatus Boulenger 1905, S. njassae Keilhack 1908, S. woosnami Boulenger 1911, S. macrostigma Boulenger 1911, S. leopardinus Pellegrin 1914, S. thamalakanensis Fowler 1935, S. macrostoma sp.n. and S.vanderwaali sp.n. A key to their identification is provided. Characters are discussed in terms of their contribution to the identification of the southern African species and, where possible, suggestions made concerning the value of these characters to the taxonomy of the genus as a whole. The rejection of certain characters previously used in Synodontis keys is discussed and alternatives proposed. The state of southern African Synodontis taxonomy is assessed and recommendations for future research are given