Doctoral Degrees (Zoology and Entomology)

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Open Access
The biology of gnathiid isopod parasites and their role as vectors of fish blood parasites in South Africa
(University of the Free State, 2000-12) Smit, Nicholas Jacobus; Van As, J. G.; Basson, Linda; Russell, Angela Davies
English: Research on marine fish parasites has been largely neglected in South Africa. This is especially true for the temporary fish parasites of the isopod family Gnathiidae and fish blood parasites of the family Haemogregarinidae. In this study, surveys were carried out to determine the presence of gnathiid isopods and fish haemogregarines associated with different intertidal and sub-tidal fish hosts over a period of four years, at two different localities on the South African south coast. The study also focussed on the relationship between gnathiids and haemogregarines, specifically the possibility that the gnathiid Gnathia africana Barnard, 1914 might be a vector of the fish blood parasite Haemogregarina bigemina Laveran and Mesnil, 1901. Laboratory work was conducted to elucidate the life cycle of G. cfricana. It was found that G. cfricana has three larval stages, consisting of three unfed (zuphea) and three fed (praniza) stages, with the final stage praniza larvae moulting into either male or female adults. Forty days after their last feed as praniza 3 larvae, mature females release stage 1 zuphea larvae. Detailed information was also supplied on the feeding and digestion length for each larval stage. The females of G. africana were re-described from the material collected. Furthermore, other gnathiid larvae, not resembling any of the known species from South Africa, were collected from three species of elasmobranchs as well as the evileye pufferfish. Both groups of larvae were kept in the laboratory, where they moulted into adult males that did not conform to the description of any other gnathiid species in South Africa, or worldwide. These specimens were described as new species (Gnathia pantherinum sp. n. and G. pipindae sp. n.), using light and scanning electron microscope observations. Extensive information was also provided on the final life cycle stages of G panthertnum sp. n. Special attention was given to finding distinguishing characteristics to identify females and larvae of various species in the absence of males. Comparing material in this study with information from the literature showed that the morphology of the pleotelson and cephalosome appendages of females and larvae could be successfully used as differentiating characteristics. The research conducted on fish haemogregarines led to new distribution and host records for two known species, and the description of two new, but un-named species. Development stages of H. bigemina were found in the gut of G. africana larvae that had fed on H. bigemina-infected host fish. The data obtained from these results was used to compile a complete life cycle for H. bigemina in both the fish and the arthropod host.
Open Access
Branchial monogenean parasites (Monogenea: Dactylogyridae) of characin fishes from the Okavango river and Delta, Botswana
(University of the Free State, 1998-12) Christison, Kevin William; Van As, J. G.; Basson, Linda
English: The fishes of the Okavango System, Botswana, are of considerable economical and ecological importance. Recently, scientists and local fishermen have reported a dramatic decline in the fish stocks of the Okavango River and Delta. There are many reasons for this decline to which fish parasites ~may at least be a contributing factor. In recent surveys to the Okavango, monogeneans have been found to be of the most prominent parasites infesting the Okavango fishes. The tigerfish, Hydrocynus vittatus Castelnau 1861, especially, show high infestations of the branchial monogeneans, Annulotrema pikei (Price, Peebles & Bamford 1969). The genera Annulotrema Paperna & Thurston 1969 and Characidotrema Paperna & Thurston 1968, are exclusively parasites of characiform fish in Africa. In the Okavango the characiforms are represented by five species, Brycinus lateralis ( Boulenger 1900), Hepsetus odoe (Bloch 1794), Hydrocynus vittatus, Mieralestes acutidens (Peters 1852) en Rhabdalestes maunensis (Fowler 1935), all of which, are infested by species of the genus Annulotrema and only one, Brycinus lateralis (Boulenger 1900), is infested by a species of the genus Charcidotrema. During two field trips to the Okavango System, five Annulotrema species were collected; three of which are known species and two new species. This is the first record of monogeneans from Botswana and represents the southern most distribution recorded of A. curvipenis Paperna 1969 & A. hepseti Paperna & Thurston 1969. Comparative descriptions of the three known species are given and the two new species are described as A. micralesti sp. n. and A. rhabdalesti sp. n. Mixed infestations of A. curvipenis and Characidotrema nursei Ergens 1973 were also recorded from the gills of Brycinus lateralis. This also represents the southernmost, recorded distribution of C. nursei. Investigation of histological sections revealed that although these monogeneans occurred in relatively high numbers on the gills of the fish, the pathology they caused was limited. Examination of the infestation statistics showed that these parasites exhibit site preferences to the gills on which they occurred. This preference is influenced by the number of monogeneans of the same or other species as well as the number of other parasites occurring on the gills of the fish hosts. When considering the results, these monogenean parasites do not seem to cause severe harm to the host fish. Any changes in the environment could alter the face of this parasite-host relationship dramatically and hence the potential pathogenicity of these parasites should, however, not be ignored.
Open Access
Branchial monogenean parasites (Monogenea: Dactylogyridae) of fishes from the Okavango River and Delta, Botswana
(University of the Free State, 2002-06) Christison, Kevin William; Van As, J. G.; Basson, Linda
English: The Okavango Delta has received much popularity for the host of wildlife that it sustains. More recently it has gained increasing interest for the rich diversity of fish species that occur there. The fishes of the Okavango are also becoming increasingly important as a natural resource attracting revenue to Botswana in the forms of ecotourism and aquaculture and also as an important food source for the local community. The Okavango Delta is a flood driven system and much of the fish distribution throughout the Delta and the timing of certain behavioural activities are dependent on the timing and magnitude of the flood. For the purpose of determining the distribution of fish parasites throughout the system, the distribution of the fish hosts was determined and it was found that fish community structure could be used to distinguish different habitat types within the different ecological regions. Fifty-nine of the expected 68 fish species for the Delta have been collected. These species represent 12 families of which the families Cichlidae and the Cyprinidae are the most abundant, making up about 50 percent of the species collectively. Various parasites have been collected from these fishes of which the monogeneans seem to be the most prevalent and abundant and currently represent approximately 36% of the parasites collected. Most of the monogeneans recorded thus far were representatives of the subclass Polyonchoinea. Of these, all belonged to the families Dactylogyridae and Gyrodactylidae. Of the monogenean parasites infesting the Okavango fishes, the representatives of the family Dactylogyridae were the most diverse. Genera of African dactylogyrids are either endemic to Africa or belong to genera with wider geographical ranges. In general dactylogyrids are host specific and their zoo geographical affinities are therefore linked to the faunistic origin of their hosts. The distribution of dactylogyrid species within Africa is determined by the distribution pattern of their hosts. Twenty-two dactylogyrid species comprising seven genera were recorded, of these 10 species were previously undescribed. This study represents the first records of representatives of the class Monogenea from Botswana and hence the Okavango Delta.
Open Access
Fish myxosporeans from the Okavango Delta, Botswana and the south coast of South Africa
(University of the Free State, 2003-12) Reed, Cecile Catharine; Basson, Linda; Van As, Liesl L.; Dykova, Iva
English: Myxozoans form a diverse and economically important group of endoparasites that have been intriguing researchers ever since the early1800's. These parasites are notorious, having been associated with the devastating effects many species have shown in aquaculture and fisheries industries throughout the world. Research on both freshwater and marine myxosporeans in Africa is limited to a few countries and has, until recently, been largely neglected in southern Africa. In recognition of the need to investigate the presence of fi sh-infecting myxosporeans in both the freshwater and marine environments of southern Africa, a study was initiated in 1997 investigating the biodiversity of myxosporeans infecting fi shes in two very unique southern African localities. Firstly, the Okavango River and Delta in Botswana contains one of the worlds largest inland deltas composed of about 18 000 km2 waterways. Situated in the middle of the Kalahari Desert, this pristine wetland is the only one of its kind that forms an inland delta and one of the few river systems in the world that is visible from space. The research on myxosporeans infecting marine fi shes was conducted along the Cape south coast of South Africa, which has one of the most diverse marine fauna and flora compositions in the world of which 13 % is endemic. This study aimed to review all existing literature concerning freshwater and marine fish-infecting myxosporeans in Africa, report on the biodiversity and prevalence of fi sh-infecting myxosporeans in the Okavango River and Delta, Botswana, investigate the pathogenic potential of myxosporeans infecting the Okavango fi shes, determine the taxonomic status, species biodiversity and prevalence of myxosporeans infecting fi shes along the Cape south coast, South Africa and investigate the pathogenic potential of myxosporeans infecting intertidal and surf zone fi shes along the Cape south coast of South Afri ca. The examination of 285 8 fi shes representing 14 families and 65 species on several field trips to the Okavango Ri ver and Delta from 1997 to 2001 revealed the presence of 29 different fish infecting myxosporeans representing the genera Henneguya Thelohan, 1892 and Myxobolus Btitschli, 1882. Six of these species have been described as new in three articles prior to this study. Another two new species have been recorded in this thesis, together with the records of 14 miscellaneous species that have never been described before, but require more materi al for the completion of species descriptions. During the course of nine surveys conducted along the Cape south coast of South Africa since March 1998, a total of 410 fishes representing 33 species were examined for parasitic infections. Results from these surveys revealed the presence of 15 different myxosporean species. Three species from the genus Ceratomyxa Thelohan, 1892, one species from the genus Henneguya, two from the genus Myxidium Biltschli, 1882, one species from the genus Myxobolus and one species from the genus Sphaeromyxa Thelohan, 1892 are described in this thesis. Two keys for the identification of both the freshwater, as well as marine and estuarine fish-infecting myxosporeans in Africa are presented as a conclusion to this study. The results obtained from this study have laid the foundation for the continuation of research on these parasites in southern Africa and has provided an insight into the great diversity of myxosporeans infecting southern African fishes.
Open Access
Key diagnostic characteristics of the developmental stages of forensically important calliphoridae and sarcophagidae in central South Africa
(University of the Free State, 2011-12-15) Brink, Sonja Lindsey; Van der Linde, Theuns C. de K.; Basson, Linda; Van Wyk, Pieter W. J.
English: The first insects attracted to a decomposing body are usually representatives of the Diptera, in particular members of the families Calliphoridae (blow flies) and Sarcophagidae (flesh flies). These flies will deposit their eggs (or often larvae in the case of sarcophagids) on the body, within a few hours after death, depending on environmental conditions. The immature stages will complete their developmental cycle on and around the body. As a consequence, these insects are of great importance in forensic entomology; the main area of application being the determination of the postmortem interval (PMI). One of the key pieces of information needed to calculate the PMI is the correct species identification of the immature stages. The aim of this study was to provide diagnostic descriptions for the immature stages of forensically important calliphorids and sarcophagids in central South Africa. Forensically important calliphorids prevalent in this region are Lucilia cuprina (Wiedemann), Lucilia sericata (Meigen), Chrysomya chloropyga (Wiedemann), Chrysomya marginalis (Wiedemann), Chrysomya albiceps (Wiedemann) and Calliphora vicina Robineau-Desvoidy. The sarcophagid prevalent in the region is Sarcophaga cruentata Meigen. A range of characteristics was evaluated by means of light and scanning electron microscopy and the most pertinent of these were identified for diagnostic purposes. The eggs were evaluated in terms of nine characteristics; six of which were of no diagnostic use, while three could be used to identify some of the species. The eggs of C. chloropyga and C. albiceps were indistinguishable from each other. Twelve features were identified for their possible diagnostic value in larvae. In first instar larvae five of these characteristics were of no diagnostic value, while six were useful to identify some of the species. All species could, however, be identified with the aid of the cephalopharyngeal skeleton. For second instar larvae, four of the characteristics were of no diagnostic use, but seven were useful to identify some of the species. All the species could be identified using the cephalopharyngeal skeleton. In the third instar larvae four characteristics were of no diagnostic use, but by using three other characteristics some of the species could be identified. All the species could be identified by means of five morphological characteristics (labrum, cephalopharyngeal skeleton, posterior spiracles, spiracular plate and anal area). Seven characteristics were identified for their possible diagnostic values in puparia. Five of these characteristics were useful to identify some of the species, but all the species could be identified with the aid of two of the characteristics (frontal field and bubble membrane). The ultimate aim of the study was to construct keys for use during the identification of specimens found at the crime scene. The keys that were constructed not only mapped out the pertinent diagnostic characteristics, but also considered what characteristics could be combined when a specimen was viewed from a specific angle. Since specimens often reach the forensic laboratory in less than optimal condition, it is essential that a wide range of characteristics and keys be available during identification. This will also enable the forensic entomologist to give priority to specimen preparation and the method of observation when rapid analysis is needed or where very few good specimens are available for identification. With these tools (descriptive diagnostic characteristics and keys) the identification of immature stages of calliphorids and sarcophagids found at the crime scene should be an uncomplicated exercise.
Open Access
Reproductive processes of scyphidiid peritrichs associated with limpet and haliotid hosts along the coast of South Africa
(University of the Free State, 2002-11) Peters, Helene; Basson, Linda; Van As, Liesl L.
English: During the early 19th century a lot of progress was made in clarifying reproduction patterns and cycles in the kingdom Protozoa Goldfuss, 1818. During the first half of the 20th century various scientists studied the reproductive processes of peritrichs and made valuable contributions. While thousands of recent papers exist on reproduction of ciliates, not much work has been done on epibiontic peritrichs. In this study the processes of binary fission, telotroch formation and conjugation are described for Mantoscyphidia branchi Van As, Basson & Van As, 1998, M. marioni Van As, Basson & Van As, 1998, M. midae Botes, Basson & Van As, 2001 and M. spadiceae Botes, Basson & Van As, 2001. It was also determined whether binary fission, telotroch formation and conjugation occur in a new species of Ellbiophrya Peters, Van As, Basson & Van As, in prep. Haliotids were collected from 1997 to 2002 at the De Hoop Nature Reserve on the south coast of South Africa and were also obtained from the Danger Point Abalone Farm near Gansbaai, and the Abagold Farm in Hermanus. Limpets were collected from 1993 to 2002 from the Goukamma Nature Reserve, De Hoop Nature Reserve and Keurboom Beach on the south coast; Mc Dougall's Bay and the Olifants River Mouth on the west coast; Bazley and at the rocky shores of Lake St. Lucia on the east coast of South Africa; and on the east coast of Marion Island at Boulder Beach which is situated in the southern Indian Ocean. Live symbiont specimens undergoing reproduction were observed with light microscopy and photomicrographs were taken of the various stages of binary fission, conjugation and telotroch formation. Mayer's, Harris' and Heidenhain's Iron Hematoxylin were used to stain the nuclear apparatus. The details of the infundibulum were studied by staining Bouin's fixed smears with protargol. Gills were also examined using scanning electron microscopy. Binary fission was mostly observed in M. spadiceae and also occurred earlier in M. spadiceae than in M. branchi and M. midae populations. The formation of telotrochs was mostly observed in populations of M. branchi and M. spadiceae. Throughout this study it was uncertain whether binary fission always has to occur before a telotroch can develop, or whether binary fission follows telotroch formation. Conjugation was mostly observed in populations of M. branchi and M. midae. In the Ellobiophrya species conjugation was also observed and this is the first record of conjugation in the genus Ellobiophrya (Chatton & Lwoff, 1923). It would be possible to study all these processes in detail if a suitable medium could be cultured in future.

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