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

M.Sc. / Please refer to full text to view abstract

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by Scott P. Kelly. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (p. 378-410). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.

Thesis (M.SC. (Aquaculture)) --University of Limpopo, 2011 / The present MSc dissertation emanates from seasonal surveys conducted by the fish parasitological group of the Department of Biodiversity and Aquaculture Research Unit of the University of Limpopo, Turfloop Campus. The first part of the present study was aimed at investigating the metazoan parasites of three cyprinids occurring in the Nwanedi-Luphephe Dams. The main purpose of it was to determine temporal changes in the intensity of infestation in terms of prevalence, mean intensity and abundance of parasite species parasitizing the cyprinids studied over a two year period. Ecological parameters including species host-specificity, seasonality, and gender preference and host size versus species intensity are discussed for each parasite. Altogether 152 specimens were examined for parasites and a total of 2 432 metazoan parasites of ten species were recorded. At the sampling site, all three hosts co-occurred, however, a substantial proportion of Barbus radiatus was collected from the perennial stream feeding one of the twindams. Fish were sampled by means of gill nets and electrofishing or seine netting in accordance with the habitat conditions. Hosts were killed and organs investigated for metazoan parasites. After collection of parasites, standard methods for processing individual parasites were followed. The results obtained revealed the following groups of parasites; monogeneans (ectoparasites) included Dactylogyrus spinicirrus, D. afrolongicornis afrolongicornis, D. afrolongicornis alberti, Afrodiplozoon polycotyleus, Gyrodactylus sp., and Dogielius sp. (all recorded from the gills); Crustacea, Dolops ranarum was found from the mouth cavity, gills and skin of Labeobarbus marequensis. Of these, only two specialists, both monogeneans, were found on Barbus trimaculatus namely, D. afrolongicornis afrolongicornis and D. afrolongicornis alberti. Based on morphology of the haptoral hard parts, these two species were almost similar to each other than to D. spinicirrus. The appreciable difference between D. afrolongicornis afrolongicornis and D. afrolongicornis alberti was mainly in the shape of the marginal bar. Both D. spinicirrus and A. polycotyleus were widely distributed and recorded on the gills of all hosts during all seasons. Both species were recorded for the first time on B. radiatus. Also, D. spinicirrus was recorded for the first time on the gills of B. trimaculatus. Based on comparison with the original material, the species could be identified to species level. These analyses provided sufficient evidence for restoration of Afrodiplozoon polycotyleus as a valid taxon. The existence of two species, Gyrodactylus sp. and Dogielius sp. were recorded for the first time on B. radiatus in South Africa, and this possibly represents new species. The endoparasites included the following groups: digeneans- Diplostomulum metacercariae from the eyes of Lb. marequensis, Ornithodiplostomum sp. and black spot (grubs) were recorded from B. trimaculatus. The latter was also recorded in the muscle of B. radiatus. Unidentified digenean cysts were recovered from the gills and in the body cavity of both Lb. marequensis and B. trimaculatus; nematodes were represented by Contracaecum larvae in the body cavity of both Lb. marequensis and B. trimaculatus; cestodes were represented by gryporynchid larvae from the intestine of B. radiatus. The general high prevalence and intensities of ectoparasites recorded is an indication that the Nwanedi-Luphephe Dams has a biotic mechanism which might have enabled it to sustain the growth rate of ectoparasite intra-population. There was no correlation between either fish length or condition factor and the number of parasites. The study indicated that the abundance of monogeneans is partly influenced by season and that of endoparasites was principally governed by the presence of intermediate hosts and definitive hosts. The second part of this dissertation dealt with the health status of Lb. marequensis. Fish health was assessed using condition-related indices including condition factor and a modified Health Assessment Index (HAI) and the associated Parasite Index (PI). The HAI was performed to determine and examine any macroscopic abnormalities regarding external features and internal organs. The purpose of combining the two indices was to use the infestation of the metazoan parasites found on and/or in Lb. marequensis to determine whether or not the environment they live in was healthy. Both indices together with the condition factor provided relatively simple and rapid indications of how well fish were coping in their environment. The HAI score varied amongst the four sampling seasons. The highest individual mean value was 63 in winter, followed by a score of 50 in autumn, while the lowest were 42 and 33 in summer and spring respectively. To authenticate the HAI and PI data, certain water quality variables were measured and are discussed in detail in this dissertation. The Nwanedi-Luphephe Dams are generally believed to have good water quality. This was supported in this study; conditions assessed in fish using the aforementioned indices did not differ greatly between seasons, nor did the conditions deviate appreciably from normality. The HAI values were low overall which signifies a healthy fish profile for the system. The present investigation showed the existence of differences in the occurrence of individual parasite to be linked to water temperature changes. Thus, seasonal changes do influence parasite developmental stages to a certain degree. Tested heavy and trace metals were within the permissible limits as provided by the Department of Water Affairs and Tourism (DWAF, 1996).

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The purposes of this investigation were to measure the relative levels of enzymatic and respiratory metabolism of some vertically migrating mesopelagic fishes collected from the ocean waters off Oregon and to modify and adapt an enzyme method for use as a measure of metabolic activity at sea with a minimum of equipment. A knowledge of the quantitative measure of the respiratory and metabolic rates of these organisms could be usefully applied to several problems of interest; oxygen minimum layers, vertical migration, and vertical distribution. Ten species of fishes were studied with regard to their respiratory potential as measured by succinic dehydrogenase activity. Oxygen consumption for two species was measured at various temperatures for comparative purposes. The metabolic rates calculated from the enzyme data fell within the limits of the standard metabolic rate - temperature relationships compiled from the data of several authors for fishes of the same size from various environments. The fish from the greatest depths had low metabolic rates comparable to those reported for some Antarctic and Arctic species. Metabolic rates of species of mesopelagic fish differed significantly and declined with the general depth and temperature at which the species was found. / Graduation date: 1965

Nine isolates of bacteria recovered from fish dying at marine facilities were collected from different geographic areas. The strains included: an isolate from chinook salmon (Oncorhynchus tshawytscha) reared in net pens in New Zealand, an isolate from chum salmon (Oncorhynchus keta) held at a laboratory in Oregon, USA., and seven strains recovered from tilapia (Oreochromis spilurus), silvery black porgy (Acanthopagrus cuvieri), and greasy grouper (Epinenhelus tauvina) cultured in Kuwait. All isolates were characterized by examination of morphological and biochemical properties and were confirmed to be members of the genus Vibrio. All isolates differed phenotypically from each other, from vibrios known to be pathogenic for fish, and from other named Vibrio species. Analysis of key phenotypic characteristics used to establish existing species suggested that the isolates tested were new Vibrio species. Four of the isolates (two from coldwater fish and two from warmwater fish) were selected for further study. This included determination of percent guanine plus cytosine (%G+C), comparison of growth characteristics, analysis of major 0 antigens and testing of pathogenicity. The four isolates examined had an absolute requirement for NaCl. Optimum growth temperatures varied among the isolates and were consistent with the temperature optima of the hosts from which the isolates were obtained. Serological analysis using slide agglutination, microtiter agglutination, and Ouchterlony double diffusion tests detected specific thermostable (0) antigens unique for each of the four isolates. A common minor antigen was observed between two of the other isolates from Kuwait. Experimental infections were produced in fingerling rainbow trout (Salmo gairdneri) using intraperitoneal injection of the four isolates. The pathogenicity of the two isolates from Kuwait was higher than that of the two salmonid isolates. The strains from Kuwait were used to challenge juvenile chinook salmon by waterborne exposure. The pathology produced by infection was characteristic Gram-negative hemorrhagic septicemia. / Graduation date: 1988

The marine vibrio ANT-500 is a typical psychrophile. The growth range of the bacterium at 35��� S is from a maximum growth temperature of 13.5 C to a minimum growth temperature of -2.5 C or less with the optimum near 7 C. The bacterium elaborates its chitinase enzymes between the temperatures of 1.5 and 13.5 C. The enzyme system is composed of three separate enzymes, probably two chitinases and one chitobiase. The rate limiting step of the enzyme-substrate reaction appears to follow Mechaelis-Menton kinetics. Chitin is the only substrate that induces chitinase synthesis in ANT-500. Chitinase activity was found in the digestive tracts of all species of fish sampled in Yaquina Bay, Oregon. Direct correlations were noted between gut content and chitinase activity in the gut, gut content and percent chitinoclasts in the gut, and chitinase activity and percent chitinoclasts. Fish with little or no chitinous material in their gut contents showed low or no detectable levels no chitinase activity and a low percentage of chitinoclasts, while fish with predominantly chitinous material in their gut contents showed high chitinase activity and a large percentage of chitinoclasts. Neither hydrostatic pressure up to 1000 atm nor lack of oxygen had a detrimental effect on chitinase activity from the gut of Raja binoculata. Sterile stomach fluid from Enophrys bison had no effect upon the growth rates of a pure chitinoclastic and a mixed culture of bacteria isolated from the gut of Enophrys bison; however, the gut fluid did allow for greater cell yield. N-acetyl-D-glucosamine, the end product of chitin decomposition, exhibited a ttglucose effect when added to culture medium. Both the pure and the mixed culture showed repression of growth in early log phase when grown in N-acetyl-D-glucosamine. The chitinase isolated from the gut of Enophrys bison is bacterial in origin. Tests in which the bacterial flora of the gut of Enophrys bison was eliminated by use of chloramphenicol revealed no detectable chitinase activity and no chitinoclastic bacterial populations. Fish in the absence of the antibiotic showed both significant chitinase activity and predominating chitinoclast populations. Other data strongly indicate that the chitinase in many species of marine fishes may also be bacterial in origin. / Graduation date: 1976