An integrative description of a new species of the genus Mesobiotus (Tardigrada: Eutardigrada: Macrobiotidae) from Poland

In this paper, we present an integrative description, utilizing morphological and genetic data, of a new eutardigrade species, Mesobiotus silesiacus sp. nov. The new species was discovered during research on Jasieniowa Mountain in Upper Silesia, Poland. While Mesobiotus silesiacus sp. nov. belongs to the harmsworthi group, it is distinguished from other group members i.e. Mesobiotus altitudinalis (Biserov, 1997 /1998), Mesobiotus diffusus (Binda & Pilato, 1987), Mesobiotus imperialis Stec, 2021, Mesobiotus krynauwi (Dastych & Harris, 1995), Mesobiotus romani Roszkowska, Stec, Gawlak & Kaczmarek. 2018, Mesobiotus mandalori Erdmann, Kosicki, Kayastha, Mioduchowska & Kaczmarek, 2024 and Mesobiotus wuzhishanensis Yin, Wang &Li, 2011 by several morphometric traits of the bucco-pharyngeal apparatus, claws, and/or eggs.

The morphometric findings are further supported by a comparative genetic analysis utilizing four molecular markers: 28S rRNA, 18S rRNA, COI and ITS2. Based on the compiled data, we also conducted a phylogenetic analysis using available genetic sequences of Mesobiotus representatives. The presented analysis clearly illustrates the position of the new species in the phylogenetic tree enabling also the discussion on the taxonomic composition and relatedness of other taxa within the genus Mesobiotus.