Morphological and molecular genetic data about Lernaea cyprinacea Linnaeus, 1758, collected from Esox lucius Linnaeus, 1758, in the European North of Russia (Pinega River) in 2022, were presented. Molecular genetic studies were carried out based on the analysis of COI mtDNA, 18S rDNA and 28S rDNA gene sequences. A significant genetic distance for the COI gene from individuals of the same species collected in other territories (China, Australia, South Africa, Canada, Austria, Argentina, Pakistan, Iran, India, Japan, Romania, Egypt, and Western Siberia) was revealed, which indicates the existence of a cryptic species L. cyprinacea in the European North of Russia. Analysis of 28S rDNA sequences showed the presence of two substitutions fixed in the population, which may indicate a fairly long-standing divergence of sister species. The 18S rDNA gene fragment is less suitable for identifying L. cyprinacea due to low variability compared to the other two gene regions.
Kuznetsova et al. (2026) studied this question.