Lights on tardigrade biodiversity: integrative redescription of Eremobiotus alicatai (Eutardigrada, Isohypsibiidae) with new insights on its morphology, phylogeny, and biogeography

Current knowledge on the genus Eremobiotus still remains limited. Only three species are known, mainly recorded in the Palaearctic region, with Eremobiotus alicatai representing the most common species. In the present study, an integrative re-description of E. alicatai based on the examination of a topotypic population from Sicily (Italy) is given, the morphological characters of which perfectly correspond to those of the type series collected in 1969. A second population of E. alicatai, from Tuscany (Italy), was also investigated from the morphological and the molecular point of view, allowing examining the intraspecific variability of the species. A re-analysis of the morphology of specimens of the type series, along with a morphological analysis of specimens of the two investigated populations of E. alicatai, allowed for an update and correction of certain morphological traits in the species. The topotypic and the Tuscanian populations were both investigated through a molecular approach: COI, ITS2, 18S, and 28S gene sequences were obtained, allowing to update the Isohypsibioidea phylogeny and to discuss the correct placement of the genus Eremobiotus. Moreover, the definition of the morphology of the claws of Eremobiotus-type and new observations regarding the buccal opening are discussed.