PANNING, A TECHNIQUE FOR ENRICHMENT OF THE OYSTER PARASITE HAPLOSPORIDIUM-NELSONI (MSX)

Plasmodial stages of the parasite Haplosporidium nelsoni (MSX) were enriched an average eight-fold with recovery of 60 to 80% using a process known as "panning" of hemolymph from infected oysters (Crassostrea virginica). The method takes advantage of the greater adherence of hemocytes, compared to parasites, to inert surfaces. Hemolymph from infected oysters was layered onto a Petri dish and cells were allowed to settle for 30 min. Nonadhering cells were gently washed, decanted, and placed in a second Petri dish. Maximum enrichment and recovery of parasites were obtained after three panning cycles. Viability, estimated by trypan blue dye exclusion, was greater than 95%. Parasite-to-hemocyte ratios before panning were highly correlated to those after panning, but correlation decreased with each incubation. Initial concentration of parasites, which ranged from 1.4 to 5 × 105/ml, was also significantly correlated with the percentage recovery. We suggest that other extracellular invertebrate protozoans may also be enriched by the same method, which is much simpler, gentler, and less expensive than most other cell separation procedures. © 1990.