Numerous species of Sarcocystis have been reported from wild ruminants, but none has been from Williamson's mouse deer (Tuagulus williamsoni). Here, we describe a new species, Sarcocystis tuagulusi, infecting five of 12 Williamson's mouse deer from southwest China. Mature sarcocysts are microscopic, up to 2280-μm long. The sarcocyst wall had 8.2-μm long villar protrusions, type 24. Using transmission electron microscopy, the protrusions on sarcocysts appeared as elongated, lancet- or leaf-like shapes in longitudinal sections; in contrast, the cross-sections revealed mushroom-shaped protrusions. In the core of the protrusion, a bundle of microtubules penetrated diagonally into a ground substance along the longitudinal axis. A phyogenetic analysis based on 18S rRNA and cox1 sequences suggested S. tuagulusi is closely related to Sarcocystis species from ruminants that employ felids as definitive hosts.
Keywords: Phylogeney; Sarcocystis; Tuagulus williamsoni; Ultrastrucure; Williamson’s mouse deer.