Ph.D. (Zoology) / Please refer to full text to view abstract

Please read the abstract in the section 00front of this document / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2000. / Veterinary Tropical Diseases / unrestricted

Thesis (MSc. (Veterinary Tropical Diseases)--University of Pretoria, 2009. / Includes bibliographical references. Also available in print format.

Thesis (Ph.D. (Zoology)) --University of Limpopo, 2012 / The diversity of the helminth parasites of fishes in a clear-water, subtropical Lake Tzaneen, in South Africa was investigated. Of the 527 fish specimens sampled approximately 9000 parasites were collected. There are 38 different parasite species discussed comprising 27 Monogenea, 3 Digenea, 4 Cestoda, 3 Nematoda and 1 Acanthocephala. Four new monogenean species are described and these are Dactylogyrus spp. 1 to 4. Three monogenean species are introduced as first records in Africa and these are Actinocleidus fusiformis (Mueller, 1934), Haplocleidus furcatus Mueller, 1937 and Acolpenteron ureteroecetes Fischthal & Allison, 1940. Fourteen monogenean and one acanthocephalan species are discussed as first geographical records for South Africa and these are Gyrodactylus rysavyi Ergens, 1973, Dactylogyrus brevicirrus Paperna, 1973, Dactylogyrus cyclocirrus Paperna, 1973, Dogielius dublicornis Paperna, 1973, Dogielius sp., Schilbetrema quadricornis Paperna & Thurston, 1968, Quadriacanthus aegypticus El Naggar & Serag, 1986, Quadriacanthus clariadis Paperna, 1961, Scutogyrus gravivaginus (Paperna & Thurston, 1969), Cichlidogyrus quaestio Douëllou, 1993, Cichlidogyrus halli Price & Kirk, 1967, Cichlidogyrus sclerosus Paperna & Thurston, 1969, Cichlidogyrus dossoui Douëllou, 1993, Cichlidogyrus tilapiae Paperna, 1960 and Acanthosentis tilapiae Baylis, 1948. Seven species are discussed as first records for their hosts and these are Cichlidogyrus dossoui, Cichlidogyrus halli and Acanthosentis tilapiae on Oreochromis mossambicus; Dactylogyrus sp. 1 on Barbus radiatus and Barbus trimaculatus; Dactylogyrus sp. 2 on Barbus unitaeniatus; Dactylogyrus sp. 3 and Dactylogyrus sp. 4 on Labeo molybdinus. Gyrodactylus rysavyi is the only species with a first site (gills) record. The other monogenean species discussed are Macrogyrodactylus clarii Gussev, 1961, Macrogyrodactylus karibae (Douellou and Chishawa, 1995), Dactylogyrus afrolongicornis afrolongicornis Paperna, 1973, Dactylogyrus allolongionchus Paperna, 1973, Dactylogyrus spinicirrus (Paperna & Thurston, 1968) and Cichlidogyrus philander (Douëllou, 1993). The digeneans discussed are Glossidium pedatum Looss, 1899 and the larvae of Diplostomum van Nordmann, 1832 and Clinostomum Leidy, 1856. The Cestodes discussed are Proteocephalus glanduligerus (Janicki, 1928) Fuhrmann, 1933, Polyonchobothrium clarias Woodland, 1925 and the larvae of Ligula intestinalis Goeze, 1782 and family Gryporhynchidae. The nematodes discussed are Procamallanus laevionchus (Wedl, 1861), Paracamallanus cyathopharynx Baylis, 1923 and larvae of Contracaecum Railliet and Henry, 1912. Monogenea were commonly found on the gills but less on the skin and in the urinary bladder. Digenea were found mainly in the eyes, brain and visceral cavity, with only one species (Glossidium pedatum) present in the intestines of Clarias gariepinus. Cestoda and Nematoda were found in the intestine and body cavity. Only one species of Acanthocephala (Acanthosentis tilapiae) was found in the intestines of Oreochromis mossambicus. No definite seasonal variations of infection and parasite affinities towards the sexes and the sizes of the hosts could be determined. The lake is oligotrophic with the water quality having no influence on the parasite diversity and species richness. / the University of Limpopo Research Office, and the National Research Foundation

Thesis (MSc. (Veterinary Tropical Diseases Veterinary Science))--University of Pretoria, 2009. / Includes bibliographical references. Also available in print format.

Thesis (PhD (Veterinary Tropical Diseases)--University of Pretoria, 2009. / Includes bibliographical references. Also available in print format.

Studies were conducted to determine some of the characteristics of the spring rise in faecal shedding of nematode ova by parasitized ewes in the Montreal area. [...]

Thesis (MSc (Veterinary Tropical Diseases.))--University of Pretoria, 2008. / Includes bibliographical references. Also available in print format.

No description available.

Membros do gênero Potamotrygonocestus (Eucestoda: Tetraphyllidea: Onchobothriidae) são parasitas exclusivos de raias da família Potamotrygonidae, endêmica da região Neotropical. Atualmente, são reconhecidas 7 espécies nominais para o gênero (P. magdalenensis, P. travassosi,P. amazonensis, P. maurae, P. fitzgeraldae, P. chaoi e P. marajoara), além de duas linhagens não descritas terem sido apontadas na última revisão taxonômica disponível. A taxonomia destes parasitas é tradicionalmente baseada em caracteres morfométricos e sofre com a plasticidade que a estrutura corpórea destes animais apresenta pois acaba dependente da fixação do espécime. Somada à prática comum de basear descrições em um número restrito de espécies coletados em regiões geograficamente isoladas, esta plasticidade corpórea resultou na premissa que estes parasitas apresentam baixa variabilidade morfológica. Neste estudo, foram analisados 1753 espécimes de Potamotrygonocestus, coletados amplamente na América do Sul. A análise dos parâmetros morfométricos tradicionalmente utilizados na taxonomia do gênero não mostrou utilidade na diagnose das espécies, porém os parâmetros discretos observados na morfologia do gancho mostraram-se informativos. Os ganchos são estruturas esclerotizadas cuja forma não depende da fixação do espécime, portanto possuem um enorme potencial para a resolução taxonômica destes parasitas. Baseadas na morfologia do gancho, as espécies de Potamotrygonocestus válidas foram redescritas e 4 novas linhagens foram observadas. Dentre todos os táxons observados, apenas P.chaoi e P. marajoara ainda necessitam o refinamento de sua diagnose, pois não foi possível diferenciá-los através da morfologia do gancho. Assim, uma nova chave de identificação foi proposta para Potamotrygonocestus, baseada nos caracteres discretos dos ganchos. Entre os 32 morfotipos de potamotrigonídeos amostrados neste estudo, em apenas 5 não havia infestação por Potamotrygonocestus. Estes hospedeiros restringem-se as regiões dos rios Madeira e Purus e a P. leopoldi no Xingu. Os padrões de especificidade estrita observados para grupos marinhos que se julga serem próximos a Potamotrygonocestus não se refletem no grupo dulcícola, e inclusive mais de uma espécie do gênero foi encontrada em um mesmo indivíduo hospedeiro, fato até então inédito para o gênero. / The members of the Potamotrygonocestus genus (Eucestoda: Tetraphyllidea: Onchobothriidae) are parasites that infect exclusively the stingrays of the family Potamotrygonidae, which are endemic of the Neotropical region. To date, seven species are recognized for this genus (P. magdalenensis, P. travassosi, P. amazonensis, P. maurae, P. fitzgeraldae, P. chaoi and P.marajoara) and two undescribed lineages were cited in the last taxonomic revision published. The taxonomy of these parasites is traditionally based on morphometric characters and therefore relies on soft tissue structures whose observed morphology is highly dependent on the fixation method used. This, in addition to the use of a restricted number of specimens from distant localities on taxonomic studies, led researchers to believe in a low morphological variation for the genus. In this study, 1753 Potamotrygonocestus specimens were examined from almost all of the South American basins. The traditional morphometric parameters for the genus taxonomy were not useful for species diagnosis, but the discrete parameters from the morphology of the hooks were shown to be informative characters. The hooks are sclerotized structures and its shape is not dependent on the fixation of the specimen, therefore having a great potential to distinguish species. Based on the morphology of the hooks, the Potamotrygonocestus nominal species that were recognized were redescribed and four new lineages were found. Among all the taxa examined, only P. chaoi e P. marajoara still need a detailed diagnosis, because it was not possible to distinguish these two species based on the morphology of the hooks. Based on the data at hand, an inference key for species of Potamotrygonocestus is proposed based on the morphology of the hooks. Among the 32 potamotrygonids morphotypes obtained for this study, only five were not infected by Potamotrygonocestus. These hosts were restricted to the Madeira and Purus basins and for P.leopoldi from the Xingu River. The host-specificity observed for the parasite worms of marine elasmobranchs closely related to Potamotrygonocestus were nor found in this freshwater genus Additionally, more than one species of Potamotrygonocestus were found infecting the same host specimen, an occurrence never noted for this parasite taxon.