The phylogenetic position of Spironucleus sp. (Diplomonadida: Hexamitidae) from the intestine of Chinese sleeper Perccottus glenii Dybowski, 1877 (Actinopterygii: Odontobutidae).
Introduction: The Chinese (Amur) sleeper (Perccottus glenii Dybowski, 1877) (Actinopterygii: Odontobutidae) is a freshwater fish species with high invasive potential. Diplomonads have been detected in the intestines of Chinese sleepers using light microscopy. Aim: The aim of this study was to identify the diplomonads in Chinese sleepers using molecular-genetic methods. Materials and methods: The fish used in this analysis were caught in the following bodies of water in Russia between 2014 and 2016: Lake Dolgoe, the floodplain of the Ingoda River (Amur River basin), the Tsna River (the Oka River basin), and the littoral of the Kotlin Island (Gulf of Finland). Partial sequences of small subunit rRNA genes were obtained for the intestinal diplomonads of Chinese sleeper. Results: The analysis of all sequenced samples revealed the presence of Spironucleus salmonis Moore, 1922; other Spironucleus species were not found in the sampled fish. With 82% probability, the sampled sequences of diplomonads from Chinese sleeper formed a separate cluster in the clade of S. salmonis on the phylogenetic tree. Conclusion: This is the first record of S. salmonis in fish in the family Odontobutidae.