Morphological and molecular characteristics of four Sarcocystis spp. in Canadian moose (Alces alces), including Sarcocystis taeniata n. sp

Abstract

Individual sarcocysts were isolated from fresh or alcohol-fixed muscle samples of two moose from Alberta, Canada, and examined by light (LM) and scanning electron microscopy (SEM) and molecular methods, comprising polymerase chain reaction (PCR) amplification and sequencing of the complete18S rRNA gene and the partial cytochrome c oxidase subunit I gene (cox1). By LM, four sarcocyst types were recognized, and the sequencing results showed that each type represented a distinct species, i.e. Sarcocystis alces, Sarcocystis alceslatrans, Sarcocystis ovalis and Sarcocystis taeniata n. sp. The finding of S. alceslatrans and S. ovalis has been reported briefly previously, but further details are provided here, including the ultrastructure of sarcoysts of S. alceslatrans as seen by SEM. The species S. alces was found for the first time in Canadian moose, whereas the finding of S. taeniata is the first record of this species in any host. The sarcocysts of S. taeniata were sac-like and about 1,000-1,100 × 60-80 μm in size. By LM, the cysts had a thin and smooth wall with no visible protrusions, whereas SEM revealed that the cyst surface had sparsely but regularly distributed, thin ribbon-like protrusions, about 2 μm long and 0.2 μm wide, lying flat against the surface and leaving most of the cyst surface naked. Similar protrusions have previously been reported from Sarcocystis grueneri in reindeer, which was found by sequence comparisons and phylogenetic analyses to be the species most closely related to S. taeniata. The phylogenetic analyses further suggested that S. taeniata, like S. alces and S. alceslatrans, use canids as definitive hosts, whereas corvid birds are known definitive hosts for S. ovalis. In contrast to the three other species found, S. taeniata displayed considerable intra-specific and intra-isolate sequence variation (substitutions, insertions/deletions) in certain regions of the 18S rRNA gene.