| Summary: | The overall goal of this project was to develop biomarkers for mussel leukemia, a sublethal endpoint used in population health monitoring. The most common method for leukemia assessment is hematocytology, which is labour intensive and subject to bias. In this thesis, new biomarkers based on DNA ploidy detection and genotyping, were developed and compared with hematocytology. These new biomarkers would allow for more sensitive and efficient monitoring of near-shore ecosystems. Two Mytilus species, M. trossulus and M. edulis, were tested. Samples were obtained from Hopkins and Horseshoe Bay beaches, a mussel farm (Island Scallops, BC) and from caged mussels of the same origins submerged at a monitoring site in Burrard Inlet and a reference site off the Sunshine Coast.
Three single nucleotide polymorphisms (SNPs) were detected within the coding region of p53 amplified from M. trossulus haemocyte cDNA, which were associated with leukemia. Many more polymorphic sites were found in M. edulis, some correlated with leukemia. Blocks in the p53 coding region sequences from late leukemic M. edulis were homologous with the M. trossulus p53 sequences, suggesting that hybridization may have contributed to increased disease susceptibility. Correlations between genotype and disease were not found in beach mussels or in either mussel species with early stages of leukemia.
DNA content flow cytometry patterns for M. trossulus haemocytes could distinguish healthy animals from diseased for all stages of leukemia, including early ones, where haemolymph contains mixtures of healthy and neoplastic cells. No strong association was observed between ploidy and leukemia in M. edulis. This new method for M. trossulus leukemia detection is recommended for monitoring of marine ecosystems exposed to multiple stressors, for which leukemia is a valuable endpoint together with other biomarkers required for efficient environmental management.
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