New multilocus phylogeny reorganises the family Macrobiotidae (Eutardigrada) and unveils complex morphological evolution of the Macrobiotus hufelandi group

Integrative descriptions of two new Macrobiotus species (Tardigrada, Eutardigrada, Macrobiotidae) from Mississippi (USA) and Crete (Greece)

“…nov. possesses 2-8 tentacular arms on the distal part of its egg processes, as opposed to 'well-developed discs', it falls outside the current definition of the group. Very similar egg processes are also present in M. anemone, which was previously included in the M. persimilis complex by Stec et al (2021) without any elaboration on that issue (please see Table 5 in Stec et al (2021) for the list of species included there in the complex). Therefore, to avoid inconsistency in accommodating these two species within the M. persimilis complex, we propose an upgraded definition that reads: species with white body, hufelandi type claws and with single-walled egg processes (without the labyrinthine layer = not reticulated) in the shape of truncated cones terminated with a well-developed disc or tentacular arms and with a solid chorion surface (the surface can be wrinkled and sometimes with faintly visible micropores but never properly porous or reticulated).…”

“…Thanks to the phylogenetic analysis performed in this study we confirmed Macrobiotus annewintersae sp. nov. to belong to the Macrobiotus persimilis complex (as defined by Stec et al 2021). Nevertheless, the morphological definition provided by Stec et al (2021) does not encompass the extraordinary egg phenotype exhibited by Macrobiotus annewintersae sp.…”

“…nov. to belong to the Macrobiotus persimilis complex (as defined by Stec et al 2021). Nevertheless, the morphological definition provided by Stec et al (2021) does not encompass the extraordinary egg phenotype exhibited by Macrobiotus annewintersae sp. nov., indicating the need for further amendment of the characters describing this monophyletic group of species.…”

“…The phylogenetic reconstruction (Figure 19) recovered the genus Macrobiotus as well as the three clades found by Stec et al (2021) and by Kiosya et al (2021) to be monophyletic. All three clades have high support values (pp=1).…”

“…materials 1, 2. Tardigrade taxonomy follows Bertolani et al (2014) and Stec et al (2021). Thorpe´s normalisation was performed with the R software (R Core Team 2020) on the morphometric traits following Bartels et al (2011)…”