Molecular assays for the detection of invasive ...



Title Molecular assays for the detection of invasive tunicates and phylogeography of a tunicate invasion in Prince Edward Island
Author(s) Sarah Elizabeth Stewart-Clark
Date 2010
Institution University of Prince Edward Island
Supervisor(s) Jeff Davidson, Spencer Greenwood
Committee member(s) Thomas Landry, Fred Markham, Fred Kibenge
Degree earned Doctor of Philosophy
Place published Charlottetown, P.E.I.
Abstract There are currently four invasive tunicate species which are causing significant challenges to the aquaculture industry in Atlantic Canada: Ciona intestinalis, Styela clava, Botryllus schlosseri and Botrylloides violaceus. These tunicates foul mussel socks, aquaculture gear, boat hulls and wharves. As with many aquatic invasive species, detection of these tunicates mostly occurs once adult populations have reached significant population sizes. However, once populations have reached these levels, there is often little that can be done to stop or slow the invasion. Having efficient and sensitive assays that could detect invasive tunicates at microscopic stages would be advantageous as management strategies could be implemented before populations spike to invasive levels. Such an assay would also be useful in monitoring mussel processing plant effluent so that invasive tunicate eggs and larvae are not spread through effluent water discharge to adjacent bays. Molecular assays have been developed in this study that can detect the four invasive tunicate species in both mussel processing effluent water and in bay water surrounding mussel leases. These assays are highly specific and have a sensitivity of detection of 1-5 eggs and/or larvae per water sample. In addition qRT-PCR assays have been developed that can detect and distinguish between different life stages of Ciona intestinalis (egg and larvae) in water samples. This qRT-PCR assay also has the capacity to evaluate viability of free swimming larvae so that nonviable larvae do not cause false positives during mussel processing plant effluent monitoring. The high throughput capacity, high specificity and sensitivity of these assays shows excellent potential for use as a monitoring tool for aquatic invasive species in screening ballast water, effluent waste from shellfish processing plants, as well in local bays and rivers. This study also used phylogenetic analyses of the cytochrome oxidase 1 gene to determine that populations of Botryllus schlosseri in Prince Edward Island have low genetic diversity. Only two haplotypes of B. schlosseri were found in this study in PEI, one which was found in all aquaculture bays tested and the other found only on native substrate in one bay. It is likely that local activity spread this species to other areas of Prince Edward Island after the initial invasion. Phylogeographic analysis suggests that this species was likely transported from Massachusetts to Nova Scotia and then was transported to Prince Edward Island via local boating activity or through the movement of aquaculture species. Through the development of these efficient detection methods and by determining source populations and possible vectors responsible for transporting invasive species to this region, it is hoped that new invasions of aquatic invasive species can be prevented and/or managed before they pose a risk to the aquaculture industry in Prince Edward Island.
Use/Reproduction The author has agreed that the Library, University of Prince Edward Island, may make this thesis freely available for inspection. Moreover, the author has agreed that permission for extensive copying of this thesis for scholarly purposes may be granted by the professor or professors who supervised the thesis work recorded herein or, in their absence, by the Chairman of the Department or the Dean of the Faculty in which the thesis work was done. It is understood that due recognition will be given to the author of this thesis and to the University of Prince Edward Island in any use of the material in this thesis. Copying or publication or any other use of the thesis for financial gain without approval by the University of Prince Edward Island and the author"s written permission is prohibited. Requests for permission to copy or to make any other use of material in this thesis in whole or in part should be addressed to: Chair of the Department of Pathology and Microbiology Faculty of Veterinary Medicine University of Prince Edward Island Charlottetown, P. E. I. Canada C1A 4P3

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