Ultrastructurally, the merozoite has many special features related to RBC invasion. Its whole surface bears a thick bristly coat4, each bristle being a clump of thin(2–3 nm) filaments anchored at their bases to the plasmamembrane (PM), as in other species of Plasmodium, suchas P. knowlesi13. The filaments are used by the parasiteto capture a RBC, but are later cleaved from the mero-zoite surface as it enters the host cell4,14–16. The chemical identity of the filaments remains uncertain. The bestcandidate is the merozoite surface protein (MSP) 1complex, comprising the most abundant proteins of the merozoite exterior, and known to be cleaved and, inmost part, shed during invasion17. Beneath the mero-zoite PM, attached to it by filamentous cross-bridges12,lie two more membranes, the three together formingthe pellicle. The deeper two membranes are the outer and inner leaves of a flattened membranous sac