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D.Phil. / Please refer to full text to view abstract

M.Sc. (Zoology) / Please refer to full text to view abstract

M.Sc. (Zoology) / The trilobic processes lateral on the cephalon were found not to be a constant feature and varied from well developed to nearly absent. A conical structure and minute openings on the dorsal surface of the antennae were found, as well as a number of small openings ventrally on the cephal on and abdomen. Mouthparts including the labrum, mandibles, maxillules and maxillae were described with the aid of electronmicrographs. An additional seta was found on the second leg, changing the original armature formula. All recorded host fishes infested by species of Mugilicola are estuarine fishes, and with the exception of two, the host fishes are mullets (Mugilidae). A diagnostic species compendium of the genus Mugilicola is presented, and is composed from available literature as well as additional information obtained from the study. The family Therodamasidae and genera are placed within the family Ergasilidae. Ecological data were obtained from five surveys conducted between January 1995 and January 1996. Mean intensity, abundance and prevalence were determined. The influence of the physical water quality parameters on AI. smithae were analyzed. Results showed no preference towards male or female host fishes. Mean intensity, abundance and prevalence showed no correlation to small changes in the physical parameters. Infested hosts were between 200 - 300mm in length and the lengths of the parasites varied throughout the year. There was no correlation between the above mentioned and seasons. From the results obtained it became clear that AI. smithae is a continious breeder. Histological studies were conducted on the alimentary canal. Results showed that the alimentary canal consists of three parts: a foregut, midgut and hindgut. The foregut is composed of the mouth and a chitinized oesophagus, terminating in a muscular bulbus. The midgut is composed of three regions: the anterior midgut with little differentiation in the epithelium cells, a middle zone with epithelium cells that vary greatly in size and shape, and a posterior region. A short chitinized hindgut opens into a dorsally situated anus.

Collections of Saprolegniaceous fungi were made from diseased tropical fish. Nineteen strains, representing three fungal genera (<u>Saprolegnia</u>, <u>Achlya</u> and <u>Pythium</u>), were isolated from 11 fish species. Due to difficulty in inducing sexual fruiting, only two strains were identified to species; both of these being <u>A. americana</u>. Laboratory infection studies revealed the ability of strains of each different fungus to infect five selected tropical fish species. <u>Saprolegnia</u> sp. and <u>A. americana</u> proved to be more vigorous and lethal pathogens than <u>Pythium</u> sp. No indications of host specificity were evident. All chemicals tested (Table 4) showed definite fungicidal abilities. No effective fungicidal concentration of the chemicals tested would permit sustained fish culturing. Malachite green was the most effective fungicide tested, being functional in concentrations as low as 2 ppm. / Master of Science

Thesis (Ph.D. (Zoology)) --University of Limpopo, 2021 / The present study was conducted to evaluate the morphological and molecular characterisation of species of Dactylogyrus parasitising Enteromius spp. from the Limpopo River System, South Africa. In addition, the study was intended to establish host-parasite associations from this system. A total of 95 host specimens were collected from eight localities between 2015 and 2016 within the Limpopo River System. Fish hosts were collected using gill nets, seine nets, fyke nets, and an electric shocker. From these, three host species were identified, E. afrohamiltoni, E. unitaeniatus, and E. trimaculatus where after monogenean parasites were retrieved from the gills using stereo microscopes. Morphometric analysis of the haptoral hard parts and male copulatory organs were studied for species identification, supported by nuclear ribosomal DNA sequences of the partial 18S rDNA region and the entire ITS-1 and partial 5.8S rDNA region, and the partial 28S rDNA region. Examination of E. afrohamiltoni revealed the presence of D. afrohamiltonii which is the first record of a monogenean parasite from this host. In addition, E. unitaeniatus revealed the presence of two species of Dactylogyrus: D. letabaensis and D. limpopoensis which are the first record of monogenean parasites from this host. The remaining Dactylogyrus species were retrieved from E. trimaculatus, namely, D. afrolongicornis, D. allolongionchus, and D. myersi. Enteromius trimaculatus harboured five of the species retrieved. The two species, D. afrolongicornis and D. allolongionchus were the most abundant from six of the eight localities studied, followed by D. myersi abundant in five of the eight localities. Dactylogyrus afrohamiltonii was considered a strict specialist, while the remaining species were considered to be intermediate specialists. Forty-one sequences of the partial 18S rDNA and the entire ITS-1 and partial 5.8S rDNA region and 19 sequences of the partial 28S rDNA region of Dactylogyrus species, including Pseudodactylogyrus anguillae were included to reconstruct the phylogenetic relationships. Based on this, molecular analysis of D. afrolongicornis from Enteromius hosts were recorded for the first time for the combined 18S rDNA and the entire ITS-1 and partial 5.8S rDNA region. The analysis revealed several groupings of Dactylogyrus species inferred largely from European cyprinoids and corresponded to host specificity. From the partial 28S rDNA, three clades were revealed linked to their biogeographical regions. Phylogenetic analysis from the 28S rDNA suggests that D. aspili from E. macrops and D. afrolongicornis are closely related. / National Research Foundation (NRF) and DST Innovation Scholarship and the Vlaamse Interuniversitaire RaadUniversity Development Corporation (VLIR-UOS)

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