Shklyar A.A.*, Mesentsev Y.S., Chikadze E.D., Smirnov A.V. 2026. Distribution of Thecamoeba aesculea (Amoebozoa: Discosea) and molecular identification and description of its sibling species — Thecamoeba sonatina sp.n. // Invert. Zool. Vol.23. No.3: 351–366 [in English].
Department of Invertebrate Zoology, Faculty of Biology, St. Petersburg University, 7/9 Universitetskaya Emb, St. Petersburg 199034 Russia.
* Corresponding author
Arseniy Shklyar: a.shklyar@spbu.ru; https://orcid.org/0009-0003-2584-0225
Yelisei Mesentsev: e.mezentsev@spbu.ru; https://orcid.org/0000-0002-2541-1207
Elizaveta Chikadze: st107864@student.spbu.ru; https://orcid.org/0009-0006-4544-5013
Alexey Smirnov: alexey.smirnov@spbu.ru; https://orcid.org/0000-0002-9844-5344
doi: 10.15298/invertzool.23.3.01
ABSTRACT: For a long time, the genus Thecamoeba was considered one of the few genera of naked lobose amoebae whose species could be reliably distinguished using light microscopy alone. However, molecular investigations have revealed genetic diversity within some “classical” species. Therefore, groups of sibling species within the genus Thecamoeba have been established. Amoebae in these groups can be reliably identified only based on molecular data. We studied three molecularly confirmed strains of T. aesculea isolated from geographically distant habitats and, using new data, refined the morphological characteristics of this species. In addition, we isolated and studied two cultures of amoebae that exhibit minor morphological differences in nuclear structure and locomotive form from T. aesculea. Analysis of molecular data revealed significant differences between these strains and other T. aesculea cultures, so we describe a new terrestrial species — Thecamoeba sonatina sp.n. Together, T. aesculea and T. sonatina sp.n. form a monophyletic group, which we designate as the “T. aesculea species group”. This is the fourth species group currently recognized within the genus Thecamoeba.
KEY WORDS: 18S rRNA gene, free-living amoeba, distribution, phylogeny, systematics, Amoebozoa.
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