INVITRO-PROPAGATION OF THE PROTOZOAN PERKINSUS-MARINUS, A PATHOGEN OFTHE EASTERN OYSTER, CRASSOSTREA-VIRGINICA

Perkinsus marinus, a pathogen of eastern oysters (Crassostrea virginic a), has been successfully propagated in vitro. Cultures of the parasit e were initiated from heart fragments of an infected oyster. The cultu red protozoan (designated Perkinsus-1) was similar in morphology at bo th the light and transmission electron microscopy levels to histozoic stages of P. marinus in naturally infected oysters. In addition, cultu red cells incubated in fluid thioglycollate medium produced enlarged c ells (prezoosporangia) that stained blue-black in Lugol's solution, a response characteristic to Perkinsus spp. and used in routine diagnosi s. Polyclonal antibodies raised against P. marinus prezoosporangia rea cted positively to Perkinsus- 1. Finally, the cultured cells infected susceptible oysters and reisolation of Perkinsus-1 cells was possible from the hearts of experimentally infected oysters. The culture medium contained most of the known constituents of cell-free hemolymph of oy sters. The success achieved in culturing P. marinus will allow further investigations aimed at reducing mortalities caused by this important oyster pathogen and at addressing many unanswered questions about its biology and pathobiology.