Perkinsus marinus (Mackin, Owen. Malcolm & Collier, 1950, Levine 1978, Dermo) was described (as Dermocystidium marinum) from Barataria Bay, Louisiana, Gulf of Mexico, as a result of studies of Eastern Oyster (Crassostrea virginica) mortality. It was initially classified as a fungus, and later as a protozoan. Currently, it is placed in the Kingdom Chromista, phylum Myzozoa. It is a microbial parasite of the Eastern Oyster, Crassostrea virginica, associated with oyster die-offs. In Chesapeake Bay, Perkinsus marinus was first identified in oyster samples from the Rappahannock River, collected in 1949, during a period of extensive oyster mortality. In estuaries north of Chesapeake Bay, appearances of P. marinus with often associated with oysters transplanted from Chesapeake Bay, 1955 in Delaware Bay, 1982 in New Jersey coastal bays, 1991 in Raritan Bay, and occurrences from Long Island to Damariscotta Bay, Maine in the 1990s. The range expansion of Dermo is believed to be associated both with oyster transplants and climate change. Within Chesapeake Bay, the expansion of the disease in the upper Bay was associated with droughts, while the northward expansion is attributed, in part to climate change, and to the evolution and spread of cold-resistant strains. Perkinsus marinus has not been reported from Canada, or from the West Coast of the US.. However, it has been found in tropical Mexico in the amphi-American Charru Mussel (Mytella strigata) in the Gulf of California, and from the cultured Pacific Oyster (Magallana gigas), the native Pleasure Oyster (Crassostrea corteziensis), and several other native bivalve species from Tropical Pacific Mexico. This parasite has been found in introduced Eastern Oysters (Crassostrea virginica) in Pearl Harbor, Hawaii.
Photo Perkinsus marinus in histological sections of the connective tissue in the digestive gland ntestinal epithelium (Fig. 4) of Crassostrea virginica from Maryland, USA. Haematoxylin and eosin stain.https://www.dfo-mpo.gc.ca/science/aah-saa/diseases-maladies/pmdoy-eng.html