In vitro propagation of two Perkinsus species from the softshell clam Mya arenaria

Two continuous, axenic cultures of Perkinsus spp. (H49 and G117)were obtain ed from the softshell clam Mya arenaria collected from Swan Point in the Ch ester River, Chesapeake Bay (Maryland). Isolate H49 was obtained from the hemolymph of a heavily infected clam. Exc ept for their larger size, H49 trophozoites and schizonts exhibited the cha racteristic morphology of Perkinsus marinus and divided by schizogony. Isol ate G117 was obtained from a combined gill/palp sample of a moderately infe cted clam. Unlike H49, vegetative forms (trophozoites and schizonts) of G11 7 were present along with prezoosporulation stages in the same culture. In culture, G117 cells multiplied by both schizogony and successive bi-partiti on. Both H49 and G117 cells reacted positively with anti-Perkinsus marinus poly clonal serum and formed hypnospores upon incubation in Ray's fluid thioglyc olate medium that stained black with Lugol's iodine. This is the first isol ation of Perkinsus species from the softshell clam. Studies to determine th e infectivity, pathogenicity, enzyme activities, and genotyping of both sof tshell clam Perkinsus spp. are ongoing.