Characterisation of the population genetics of farm-bred Haliotis midae using microsatellite DNA markers
Master Thesis
2006
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University of Cape Town
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Abstract
The abalone Haliotis midae is a gastropod mollusc which is of commercial importance in South Africa due to its high export value. During this study the genetic structure of farmed Haliotis midae was investigated in order to determine whether microsatellite DNA analysis could be used to separate farmed abalone into phenotypically different groups with respect to growth rate. Microsatellites display high levels of variability and this makes them suitable for a wide variety of applications in aquaculture, particularly where genetic differentiation between population groups may be limited. This study investigates the genetic composition of 120 individuals from 2 spawning events that had been classed as either fast or slow growing by the farm managers. Three highly polymorphic microsatellite loci were selected and used to determine the extent of the genetic diversity which exists amongst the 120 individuals tested from the lacobsbaai abalone farm. Additionally, these microsatellite loci were used to determine whether abalone classed as either fast or slow growing could be differentiated into specific genetic population groups. Neighbour-joining trees constructed using genetic distance data obtained for all three loci demonstrated that a distinct separation between the fast and slow growing abalone was evident. It was also found that there has been a loss of genetic diversity on the lacobsbaai abalone farm in terms of heterozygosity. This has been attributed to the high levels of inbreeding as evidenced by the high Fis values. All population groups were found to deviate significantly from Hardy-Weinberg equilibrium and this is most likely due to the occurrence of non-random mating on the lacobsbaai abalone farm. This study has successfully demonstrated that a combination of micro satellite loci with high allelic diversity can potentially be employed as a tool for distinguishing between fast and slow growing farmed abalone. This study needs to be validated by testing larger sample sizes and the use of additional farms.
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Includes bibliographical references (leaves 89-94).
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Naidoo, R. 2006. Characterisation of the population genetics of farm-bred Haliotis midae using microsatellite DNA markers. University of Cape Town.