The first report on the occurrence of an actinosporean stage (Myxozoa) in oligochaetes in the coastal zone of Lake Baikal.

At the end of June 2019, out of 1000 oligochaetes, consisting of several species, collected in the coastal zone of Lake Baikal at a depth of 1 m, 1 specimen of the oligochaete (0.1%) was infected with actinospores of Triactinomyxon type MNV. Actinospores developed in the intestinal epithelium of the oligochaete. Hypertrophy and death of infected epithelial cells were observed. The nucleotide sequence of the 18 S rDNA gene region with a length of 1064 bp was deposited in the Genbank database under the number PP575756. Sequence comparison in the Blast program revealed that Triactinomyxon type MNV is 97.51% similar to and 91% similar to Triactinomyxon type "changzou". Phylogenetically, Triactinomyxon type MNV clusters with species that infect cyprinids.