Novel integrative data for two Milnesium Doyère, 1840 (Tardigrada: Apochela) species from Central Asia

Macrobiotus rebecchii sp. nov.: A New Limno-Terrestrial and Hermaphroditic Tardigrade from Kyrgyzstan

A new tardigrade species of the genus Macrobiotus C.A.S. Schultze, 1834 from Kyrgyzstan, is described and illustrated in this paper. Macrobiotus rebecchii sp. nov. is a hermaphroditic and limnoterrestrial species found in a moss growing on a rock in Toluk village. Specimens of the new species were examined for its morphological details using contrast phase light microscope (PCM) and scanning electron microscope (SEM). Genetic data in the form of DNA sequences of commonly used molecular markers were also obtained (18S rRNA, COI). Phenotypically the new species is most similar to Macrobiotus joannae Pilato & Binda, 1983, Macrobiotus punctillus Pilato, Binda & Azzaro, 1990, and Macrobiotus hannae Nowak & Stec, 2018, but can be easily differentiated from all of them by its body granulation pattern.

Reaching the Monophyly: Re-Evaluation of the Enigmatic Species Tenuibiotus hyperonyx (Maucci, 1983) and the Genus Tenuibiotus (Eutardigrada)

Revisions and redescriptions of taxa described in the past and that are now categorized as insufficiently diagnosed often play a crucial role in making further progress in modern taxonomy in many groups of organisms. Here we revised an enigmatic tardigrade species Tenuibiotus hyperonyx (Maucci, 1983) based on the newly discovered topotypic population from the Italian Alps. We performed an integrative analysis of morphological and genetic data in order to present an upgraded species description and elucidate its phylogenetic position. Our results enabled us to confidently place T.hyperonyx within the family Richtersiusidae, as a member of the genus Diaforobiotus. This change, together with a re-assessment of microphotographs of the Tenuibiotus willardi (Pilato, 1977) and Tenuibiotus bozhkae Pilato, Kiosya, Lisi, Inshina & Biserov, 2011 types, led to the discussion on species composition with narrative taxa amendments for the taxonomic parties involved in the proposed alteration.

Molecular Phylogenetics, Speciation, and Long Distance Dispersal in Tardigrade Evolution: A case study of the genusMilnesium

Microorganisms (sensu lato, i.e., including micrometazoans) are thought to have cosmopolitan geographic distributions due to their theoretically unlimited dispersal capabilities, a consequence of their tiny size, population dynamics, and resistant forms. However, several molecular studies of microorganisms have identified biogeographic patterns indicating cryptic speciation and/or weak species definitions. Using a multi-locus approach with the genus Milnesium (Tardigrada), we aimed to determine the genetic structure of populations worldwide and the effects of long distance dispersal (LDD) on genetic connectivity and relationships across the six continents. Our results on this micrometazoan's genetic structure and LDD at global and micro-local scales indicate contrasting patterns not easily explained by a unique or simple phenomenon. Overall, we report three key findings: (i) confirmation of long distance dispersal for tardigrades, (ii) populations with globally-shared or endemic micro-local haplotypes, and (iii) a supported genetic structure instead of the homogeneous genetic distribution hypothesized for microorganisms with LDD capabilities. Moreover, incongruences between our morphological and molecular results suggest that species delimitation within the genus Milnesium could be problematic due to homoplasy. Duality found for Milnesium populations at the global scale, namely, a molecular phylogenetic structure mixed with widely distributed haplotypes (but without any apparent biogeographic structure), is similar to patterns observed for some unicellular, prokaryotic and eukaryotic, microorganisms. Factors influencing these patterns are discussed within an evolutionary framework.