Fig. 2

Light microscopic and ultrastructural morphology of sarcocysts from Maxomys whiteheadi in Borneo (a–c) and wild Rattus norvegicus in China (d, e). Note, due to ethanol fixation some ultrastructural details of the samples from Borneo are poorly resolved. a Richardsen’s dye-stained 1.0-µm thin section through a mature sarcocyst showing the villar protrusions (PT) of the cyst wall and numerous relatively small cystozoites (CZ). b Same sample as before under the electron microscope; note the thin layer of ground substance underneath the protrusions. c Enlarged part of the interior of the sarcocyst showing cystozoites—although with limited resolution—that possess a pair of rhoptries each, which is characteristic for this Sarcocystis species (black and white arrows; compare with Fig. 1d). d Live sarcocyst isolated from striated muscle tissue of a wild Norway rat in China; the inset shows live cystozoites that were freshly released from a cyst. e Ultrastructure of the same sarcocyst as before; note that the villar protrusions are highly similar to the samples from Borneo and Thailand regarding size and shape (Fig. 1e); again, cystozoites only exhibit one pair of rhoptries (arrows) and relatively few micronemes