Masters Degrees (Zoology and Entomology)
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Browsing Masters Degrees (Zoology and Entomology) by Author "Basson, Linda"
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Item Open Access Aspects of the morphology, life cycle and epidemiology of Toxocara species and Toxascaris Leonina(University of the Free State, 2003-03) Tekele, Girma Mekete; Kok, Dawie J.; Basson, LindaEnglish: The present study has provided detailed and comprehensive information on the morphological aspects, life cycle, and epidemiology of Toxocara canis, Toxocara cati and Toxascaris leonina. The overall results of the study results are briefly summarized as follows: 1. In the morphological studies of these parasites, it has been observed that there are gross morphological similarities in the developmental stages of T. canis, T. cati and T. leonina. However, closer and detailed observations have revealed that the various developmental stages differ from one another in their fine morphological features. The observed morphological differences were: a. Eggs of T. canis and T. cati look very similar under the light microscope, in some eggs it seems that the surface pits and ridges of T. canis are larger and coarser than in the eggs of T. cati. However, unlike the eggs of Toxocara spp., eggs of T. leonina have no surface pits and ridges but are smoother on the surface. b. Second-stage larvae of T. canis recovered from the eggs and from the infected tissues of mice were stumpy and vigorously motile. The larval stages from both sources were similar in their morphological features and had comparable size measurements indicating that larval stages did not undergo development in the paratenic host. Like the larvae of T. canis, second-stage larva of T. cati recovered from the eggs and from the infected tissues of mice were stumpy and vigorously motile. The larval stages from both sources were similar in their morphological features and had comparable size measurements. The second-stage larvae of T. canis recovered from eggs or from tissues of mice had a greater width than the comparable second-stage larvae of T. cati. Unlike the larval stages recovered from the embryonated eggs of T. leonina, larvae recovered from infected tissues of mice were longer and wider and had more distinct morphological features. This indicated that larval stages recovered from the tissues of infected mice had probably undergone development to third-stage larvae. c. Adults T. canis, T. cati and T. leonina resemble each other in their gross morphological features, but also differ in their detailed and fine structural features. The major differences were on the shape of cervical alae, the presence or absence of an esophageal ventriculus, the position of the vulva in the female worms, as well as the number and arrangement of papillae on the tail of the male worms. d. Precloacal median papilla were recorded and described in males of T. canis and T. cati. Previous researchers did not describe the presence of these structures in male Toxocara spp. worms. In the present study, a female T. canis worm with a length of 27.5 cm was recovered from an infected dog and it was larger than any recorded in the literature. 2. In the study of the modes of transmission of ascarids, it has been observed that transplacental transmission of T. canis occurred in mice infected during but not before pregnancy. Transmammary transmission of T. canis and T. cati larvae had also occurred in mice infected prior to or during pregnancy. However, unlike in T. canis and T. cati, had neither transplacental nor transmammary transmission occurred in T. leonina. Larval stages were recovered from most tissues and organs of infected mice, and the larvae gradually accumulated in various extraintestinal tissues for the three ascarid species and especially in the brain of mice infected with T. canis. 3. The study on T. leonina transmission to the definitive hosts through experimentally infected mice as paratenic host, has indicated that dogs can be infected by ingesting infected tissues of mice that were infected with T. leonina infective eggs originally obtained from dogs. However, in cats this was not possible and it has been suggested that cats may not be the proper definitive host for T. leonina originating from dogs. 4. In an epidemiological survey of Toxocara spp. T. leonina, and other intestinal helminths of dogs and cats in Jimma, Southwestern Ethiopia, it was shown that the overall prevalence rates for parasitic infection were 60.78% in faecal samples of dogs from the environment, 78.60% in faecal samples of dogs taken from the rectum, 66.23% in faecal samples of cats and 33.38% in soil samples were recorded. Parasite species identified were Toxocara canis, T. cati, Toxascaris leonina, hookworms, Spirocerca lupi, Trichuris vulpis, taeniids, Ascaris species and Strongyloides species. A relatively high mean egg count of 15.25 was observed for T. canis in dog faecal droppings collected from the environment. The potential of these parasites as a cause of zoonotic infections, ways of prevention of infection and control measures were discussed.Item Open Access Blood parasites of Free State and Lesotho reptiles(University of the Free State, 2003-07) Van As, Johann; Davies, Angela; Basson, LindaEnglish: The study of blood parasites of reptiles is a relatively new and unexplored field of research in South Africa. The Free State province and the Lesotho highlands provide a range of reptiles in which their intraerythrocytic parasite fauna were explored. Objectives of this study were to set a baseline of blood parasite diversity and to identify the enigmatic Sauroplasma Du Toit, 1937 and Serpentoplasma Pienaar, 1954 infections in lizards and snakes, respectively. Surveys were conducted in various localities in the Free State and Lesotho. Although low in diversity, 204 specimens representing 14 species of lizards, and 59 specimens representing 13 species of snakes were investigated for the presence of blood parasites. Three known infections were found: Sauroplasma thornasi Du Toit, 1937, Sauromella haemolysus Pienaar, 1954 and Hepatozoon (Haemogregarina) sebae (Laveran and Pettit, 1909) Smith, 1996. These were redescribed and S. thomasii and H. sebae were examined by aid of transmission electron microscopy. The investigation led to the discovery of six new records and possibly new species of haemogregarines named Hepatozoon sp. A-F, four new records and possibly new species of lizard malaria named Plasmodium sp. A-D, and a viral infection possibly of the Pirhemocyton type. Furthermore nine new host and distribution records for Sauroplasma in lizards and nine for Serpentoplasma in snakes are described. Ultrastructural investigations of S. thomasi in Cordylus giganteus A. Smith, 1844, Serpentoplasma in Bitis arietans arietans (Merrem, 1820) and H. sebae in Python sebae natalensis (Gmelin, 1789) were the first to examine the nature of infections in this manner. This is the first comprehensive survey of the biodiversity of blood parasites in reptiles in the Free State and Lesotho highlands.Item Open Access The identification of Diptera of the grave and their succession patterns during winter and summer in central South Africa, with reference to forensic applications(University of the Free State, 2016-01) Van der Merwe, Sylvia Shalomé; Brink, Sonja L.; Basson, LindaEnglish: Forensic entomology is a specialist branch of forensic sciences in which information about insects is used to draw certain conclusions when investigating medico-legal cases involving both humans and wildlife. The primary application of insects collected from a crime scene is to determine the Post-Mortem Interval (PMI). One of the principal cornerstones in the effective application of forensic entomology is the correct identification of species found at a crime scene. The estimation of PMI using succession and developmental data is dependent upon the specific species that were present on a cadaver. The aim of this study was to identify the members of the Diptera that are capable of colonising buried carrion within a Free State grassland area, as well as to compare below ground dipteran data with above ground dipteran succession patterns. The field experiments, conducted in order to determine what species of Diptera are capable of reaching buried carrion during winter and summer months, as well as to determine the succession patterns of Diptera on buried remains, were conducted on the west fields of the University of the Free State campus, in central South Africa. The area is characterised by dry mild winters and warmer summers, with occasional rainfall periods. A total of seven pigs (Sus scrofa Linnaeus 1758) were used during each season, which consisted of one above ground control carcass and six separate below ground carcasses buried at 60 cm. Below ground carcasses were left for predetermined periods of time and were excavated on separate occasions over each 120 day trial period to monitor dipteran occurrence, colonisation and dipteran interactions. Members of Diptera were found to colonise carcasses at 60 cm during both winter and summer trials. Higher dipteran species diversity was noted on the buried winter carcasses in comparison to the buried summer carcasses. Four species of Diptera, Megaselia scalaris (Loew 1866) (Phoridae), Conicera tibialis Schmitz 1925 (Phoridae), Muscina stabulans (Fallén 1817) (Muscidae) and Leptocera Olivier 1813 sp. (Sphaeroceridae) were seen to occur on winter carcasses, with first colonisation taking place from day 21 of the winter trial. Three species of the Diptera, M. scalaris, Leptocera sp., and Sarcophaga Meigen 1826, were seen to colonise buried summer carcasses, with first colonisation taking place from day 21 of the summer trial. Dipteran faunal composition on buried carcasses was noted to be different to that of Diptera on above ground carcasses during both the winter and the summer trials. Statistical analysis showed that there was a significant difference between above ground and below ground dipteran faunal similarity. Preservation experiments on immature Diptera of the grave for identification purposes showed that the standard preservation mediums used for insects of forensic importance, such as ethanol solution and formaldehyde solution, are not effective. Preservation of adult samples was successful in 70% ethanol solution. Breeding trials under laboratory conditions proved effective in breeding larval instars found on buried carcasses through to adulthood for identification. Due to the difficulty in preservation of immature individuals of Diptera of the grave, and the ease of breeding larvae of these dipteran species, identifications were done on adult specimens. Adult Diptera were described based on taxonomic criteria, including wing venation, setal hairs and the hypopygium of male phorid specimens, and a simplified identification key was successfully compiled using morphology of the adult Diptera of the grave.Item Open Access Myxosporean parasites (Myxozoa: Myxosporea) infecting fishes in the Okavango River system, Botswana(University of the Free State, 2000-06) Reed, Cecile Catharine; Basson, Linda; Van As, Liesl L.English: The Class Myxosporea Butschli, 1882 comprises an enormous group of spore forming obligatory parasites that are able to infect any organ of the hosts in which they are found. Myxosporeans mostly parasitise fish and to date there are more than 1300 species known from fishes throughout the world. In Africa, approximately 84 species have been described from primarily freshwater fish. Research on myxosporeans in southern Africa is very limited, with only a few publications appearing from the coast of South Africa during the early 20th century. In Botswana no research has ever been conducted on myxosporean parasites infecting fishes. Botswana contains one of the worlds largest inland delta systems formed by the Okavango River, which flows in a southeasterly direction from Angola. Knowledge on the fishes as well as their parasites is essential for the well being of a unique body of water such as this. Since myxosporean parasites of fish hold the potential to be pathogenic to their hosts and have been known to cause serious economical losses in aquaculture industries throughout the world, it is thus essential to determine the distribution and biodiversity of these parasites in the Okavango River and Delta in Botswana. The main aims of this project were to investigate the available literature regarding African myxosporeans, compile a database of species infecting freshwater fishes in Africa and to investigate the taxonomic status, species biodiversity and prevalence of myxosporeans infecting fishes in the Okavango River and Delta in Botswana. Fieldwork for this project was conducted in June and July 1998 and 1999 in the Okavango and a total of 275 fishes belonging to 31 species from nine different families were examined for the presence of myxosporean parasites. Five myxosporeans from the genus Henneguya Thélohan, 1892 were collected from four different fish hosts. Only one of these was identified as a known species and was described in this dissertation. A comprehensive morphological description of the four unknown species was also provided. Eight myxosporeans from the genus Myxobolus Butschli, 1882 were also found infecting nine different fish hosts, of which four were identified as known species and described. Detailed descriptions of the four unknown species were provided. It was also found that some fish species showed very high gill infections of these parasites, which may cause some form of respiratory deficiency. This current investigation into myxosporean parasites infecting fishes in the Okavango River System in Botswana provided new insight into the distribution of myxosporeans in southern Africa and has also opened the door for future research in this unique group.Item Open Access Sessiline ciliophorans associated with Haliotis species (Mollusca: Archaeogastropoda) from the South Coast of South Afica(University of the Free State, 1999-06) Botes, Heléne; Basson, Linda; Van As, Liesl L.English: Abalone, locally known as perlemoen, are herbivorous marine gastropods with all species in one genus, Haliotis Linneaus, 1758. Abalone have been commercially exploited since ancient times. Along the southern African coast, the genus Haliotis comprises six endemic species. Surveys carried out from 1995 to 1999 at the De Hoop Nature Reserve along the south coast of South Africa, revealed the presence of scyphidiid peritrichs, of the genus Mantoscyphidia Jankowski, 1980, occurring in abundance on the gills of Haliotis spadicea Donovan, 1808 and H. midae Linnaeus, 1758. These were described as two new species, i.e. M spadiceae sp. nov. and M midae sp. nov. The mantoscyphidians in turn hosted ellobiophryids of the genus Caliperia Laird, 1953, which was also described as a new species, Caliperia perlemoenae sp. nov., occurring on both mantoscyphidian species. During the study a perlemoen aquaculture facility, Danger Point Abalone Farm, was also visited, specimens of H. midae were examined and found to harbour the same species of scyphidiid peritrich and caliperid than H. midae collected from the De Hoop Nature Reserve. In the present study, severe infections of redial, cercarial and metacercarial stages and a few adult specimens of a digenean trematode were also found in the digestive gland of Haliotis spadicea as well as on the gill filaments. In order to elucidate the symbiont/host associations field experiments and histopathological examinations were carried out. These led to the conclusions that the host/scyphidiid peritrich associations are most likely not parasitic. In the case of the mantoscyphidianlcaliperid association, no clear evidence was found that the caliperids are pathogenic to their mantoscyphidian hosts. On the other hand, the trematodes could be potential pathogens since they can cause tissue destruction and affect the reproductive organs in the host.