| Abstract |
The cod populations of the Canadian Atlantic were once highly productive,
generating enormous annual harvests and attracting fishing fleets from
many nations. However, through the late 1980s improved fishing technology,
unprecedented capture rates, and poor fishery management brought wild
stocks beyond the point of collapse. Dwindling harvests in the early 1990s
resulted in cod fishing moratoriums, and an end to the productivity for
which the fishery was once renowned. Atlantic cod remains a popular food
worldwide and the collapse of cod fisheries has done little to abate
market demands. Consequently, the cod is considered a prime candidate for
aquaculture production, providing the impetus for commercial-scale farming
operations. As aquaculture efforts continue to grow, disease management
challenges have become a prominent concern. Many parasites are prevalent
on cod farms, including intracellular pathogens such as viruses and
microsporidians. Detailed research into diseases affecting farming
operations is imperative if commercial-scale cod aquaculture is to develop.
Piscine cell culture techniques represent a valuable tool for studying the
intracellular pathogens currently impeding cod aquaculture. To date
however, few cell culture models have been made available for the Atlantic
cod. This research details the establishment of a larval cod cell line,
GML-5, investigations of infective processes in microsporidian parasites,
and development of in vitro culture methods for a microsporidian parasite
of the Atlantic cod. GML-5 cells have been cultured for two years and
survived more than 26 passages in L-15 media supplemented with 10% fetal
bovine serum and incubated at 18 Celsius. The cells have tested positive
for a marker of stem cell-like characteristics, had their origin
identified as Gadus morhua by DNA barcoding, and been cryopreserved for
long-term storage. The cells have been successfully used to support the
growth of two microsporidian parasites. Infection-mediating effects of
Mg2+ and EDTA have been confirmed in a previously-untested microsporidian
species and novel pH treatments were successfully used to stimulate
infection and development of Loma morhua in GML-5 cells. The results of
this research represent the foundations of an in vitro infection model for
Loma morhua, and demonstrate shared responses to specific chemical
conditions by microsporidian parasites with highly dissimilar host species.
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