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TEMPERATURE AND RANGE EXTENSION BY PERKINSUS MARINUS
Citation:
Ford, S. E., R. Smolowitz, AND M Chintala. TEMPERATURE AND RANGE EXTENSION BY PERKINSUS MARINUS. Presented at National Shellfisheries Association Conference, Seattle, WA, March 19-23, 2000.
Description:
Between 1990 and 1992, Dermo disease of oysters, caused by Perkinsus marinus, experienced a 500-km northward range extension and is now established as far north as Massachusetts. Climate warming during the 1980s and early 1990s, combined with historical introductions of infected oysters, has been hypothesized as the cause. Surprisingly, anecdotal reports of oyster growers indicated that the disease was causing few deleterious effects in the Northeast. To document and investigate possible causes for this assertion, we monitored numerous oyster stocks between Delaware and Cape Cod Bays to describe disease cycles, to measure Dermo effects on oysters, and to compare results with data from more southern regions. We also investigated whether a low-temperature-tolerant strain of P. marinus is now present in the Northeast. Results of this two-year study showed that P. marinus behaves in its new range very much as it does in southern areas where it has been enzootic for decades. Seasonal cycles are similar, as is the 2-3 year progression to a full epizootic. Mortality during the present Study was a least as great as in the south. Temperatures in most of the growing areas examined readily became warm enough to sustain high P. marinus proliferation and winters were not cold enough to limit disease cycles. Data from an in vitro growth assay of P. marinus isolates from North Carolina to Massachusetts, suggest responses to temperature that vary along a latitudinal cline; however, there was no consistent evidence from this assay, or from in vivo proliferation, that a low-temperature-tolerant strain has invaded the Northeast.