Over the past decade a significant area of focus for eastern oyster research has been mortality trends disproportionately affecting triploid oysters. Introduced in the late twentieth century, triploid oysters, carrying three homologous sets of chromosomes, quickly gained popularity along much of the east coast as their rapid growth and meat quality made them appealing for eastern oyster aquaculture. However, across the eastern and gulf coasts there have been a growing number of reported triploid die-offs in late spring and early summer. These mortality events create a significant economic challenge prompting investigation into their cause.
Numerous potential drivers of enhanced triploid mortality including energetic imbalances, altered immune function, and dampened salinity response have been the target of this investigation. However, the vast majority of this research has exclusively focused on the organismal level. As such, there is a critical gap in our understanding of the basic cellular differences between diploid and triploid oysters, particularly those differences that may be connected to reported mortality events. To begin filling this gap, fluorescence-based flow cytometric and confocal microscopy assays were used to characterize the differences in many basic cellular characteristics between diploid and triploid oyster hemocytes. Two significant metrics evaluated as part of this research were total protein and mitochondrial levels. Additionally, flow cytometric variables such as forward and side scatter were used as proxies to compare cell size and complexity along with determining the percent composition of hemocyte populations.
Most interestingly, this approach has demonstrated a shift in triploid oyster hemocyte populations towards a larger percentage of intermediate to large, highly granular, cells. These results suggest that increased overall triploid oyster hemocyte size and granularity may be the result of differences in percent representation of certain cell subpopulations rather than shifts in cell subpopulations along these metrics.