Opaline is an unusual group of protists, characterized by the presence of flagella covering their whole body. They reside in the intestinal tracts of various animals, most notably amphibians. While there is a wealth of data regarding the morphological features of opalines, molecular data are extremely sparse. Consequently, the extent of diversity of this understudied group remains unknown. Here, we examine opalines from the intestinal tract of the amphibian Hoplobatrachus rugulosus in Thailand. We provide micrographs obtained from light and scanning electron microscopy of various opalinid morphotypes. Furthermore, we enrich the database of opaline sequences by providing new molecular data of the small subunit ribosomal DNA gene of these species. In our phylogenetic analyses, the newly derived sequences form a cluster sister to Protoopalina.
