Molecular phylogeny of Spirodinium equi, Triadinium caudatum and Blepharocorys sp. from the equine hindgut

Single cell morphotypes of the species Triadinium caudatum and Spirodinium equi, together with a representative of the genus Blepharocorys (Blepharocorys sp.) were used for phylogenetic analysis based on their 18S rRNA genes. Spirodinium equi clustered with sequences already described for the entodiniomorphs isolated from horses and the Blepharocorys sp. also grouped within the Entodiniomorphida clade, although both sequences were distinct from those described from rumen ciliates. Triadinium caudatum clustered within the Vestibuliferida, and most closely to that of Paraisotricha, only other member of this order which has been described in the horse. It was concluded that although members of the orders Entodiniomorphida and Vestibuliferida are present in the equine gut, and that they share an ancient linage with their rumen counterparts, they are ancestrally different groups.