Verification of Hypsibius exemplaris Gasiorek et al., 2018 (Eutardigrada; Hypsibiidae) application in anhydrobiosis research.

Anhydrobiosis is considered to be an adaptation of important applicative implications because it enables resistance to the lack of water. The phenomenon is still not well understood at molecular level. Thus, a good model invertebrate species for the research is required. The best known anhydrobiotic invertebrates are tardigrades (Tardigrada), considered to be toughest animals in the world. Hypsibius. exemplaris is one of the best studied tardigrade species, with its name "exemplaris" referring to the widespread use of the species as a laboratory model for various types of research. However, available data suggest that anhydrobiotic capability of the species may be overestimated. Therefore, we determined anhydrobiosis survival by Hys. exemplaris specimens using three different anhydrobiosis protocols. We also checked ultrastructure of storage cells within formed dormant structures (tuns) that has not been studied yet for Hys. exemplaris. These cells are known to support energetic requirements of anhydrobiosis. The obtained results indicate that Hys. exemplaris appears not to be a good model species for anhydrobiosis research.

Integrative description of five Pseudechiniscus species (Heterotardigrada: Echiniscidae: the suillus-facettalis complex).

Pseudechiniscus is a morphologically homogeneous heterotardigrade genus with a relatively low number of morphological features useful for the species discrimination. The species of the Pseudechiniscus suillus-facettalis complex are some of the most challenging tardigrades to identify. Here, we examine several populations from Antarctica, Italy, Madagascar and Norway that would have most likely been attributed to Pse. suillus prior to the recent redescription of the species. Populations were analysed using integrative taxonomy-a combination of classical morphology and morphometry, as well as genetic data. Besides minute differences in dorsal sculpture and morphometry, we found clear, species-specific differences in ventral sculpture which are very useful in discrimination of Pseudechiniscus species. Based on morphology (mainly ventral sculpture) and significant genetic distances in COI and ITS-2 sequences, we describe five new species: Pse. angelusalas sp. nov. from Madagascar, Pse. dastychi sp. nov. from Antarctica, Pse. ehrenbergi sp. nov. from Italy as well as Pse. indistinctus sp. nov. and Pse. lacyformis sp. nov. from Norway. Finally, we provide an updated phylogenetic tree of the genus Pseudechiniscus based on COI sequences.

Two new genera of long clawed Isohypsibioidea Guil, Jørgensen amp; Kristensen, 2019.

Two new eutardigrade genera Vladimirobius gen. nov. and Weglarskobius gen. nov. are erected for the species Grevenius irregibilis (Biserov, 1992) and Isohypsibius altai Kaczmarek Michalczyk, 2006a, respectively. They are characterized by strongly modified claws, bucco-pharyngeal apparatus of the Isohypsibius variant, pharyngeal apophyses, and placoids present. The primary branches of internal claws of Vladimirobius gen. nov. are wide in lateral view and have very prominent gibbosity-like projections, whereas primary branches of external claws are thin and extremely long. In Weglarskobius gen. nov. claws IV are similar in shape and size, but the primary branches are extremely long, and thin. Moreover, claws on legs I-III vary greatly in size and shape in Weglarskobius gen. nov. Such supposed autapomorphies fully justify erection of the two new genera, even if the genetic data are presently unavailable.

Two new species of the genus Milnesium Doyère, 1840 (Tardigrada, Apochela, Milnesiidae) from Madagascar.

The knowledge of the diversity and distribution of tardigrades on Madagascar is rather poor. To date, only 13 tardigrade taxa have been reported from this region (including one Milnesium species). We examined 46 specimens belonging to two new-to-science species of the genus Milnesium described herein using an integrative approach, including classical morphology and molecular marker (COI, ITS-2 and 28S rRNA) analysis. The species were found in two moss and lichen samples collected in the Ivohibory forest in Fianarantsoa Province. Milnesium matheusi sp. nov., with claw configuration [3-3]-[3-3] and rather wide buccal tube, morphologically is most similar to: Mil. beatae Roszkowska, Ostrowska & Kaczmarek, 2015, Mil. bohleberi Bartels, Nelson, Kaczmarek & Michalczyk, 2014, Mil. eurystomum Maucci, 1991, Mil. shilohae Meyer, 2015 and Mil. tumanovi Pilato, Sabella & Lisi, 2016; however, it differs from these by morphometric characteristics. Milnesium wrightae sp. nov., by the presence of four points on secondary branches of claws IV, is most similar to Mil. quadrifidum Nederström, 1919. However, Mil. wrightae sp. nov. differs from Mil. quadrifidum by claw configuration ([4-4]-[4-4] in Mil. quadrifidum vs. [3-3]-[4-4] in Mil. wrightae sp. nov.), but also by the position of the fourth points on secondary branches of claws IV, which are located near the base of the claw in the new species and near the top of the claw in Mil. quadrifidum. Genotypic analysis showed that Mil. matheusi sp. nov. is most similar to Milnesium sp. (28S rRNA), Mil. variefidum (COI) and Mil. t. tardigradum (ITS-2) while Mil. wrightae sp. nov. is most similar to Milnesium sp. (28S rRNA), Mil. variefidum (COI) and Mil. matheusi (ITS-2). Five Milnesium taxa are recorded from the African region, including the two new species from Madagascar reported in this study.

Variability of Echiniscus tristis Gasiorek & Kristensen, 2018-is morphology sufficient for taxonomic differentiation of Echiniscidae?

The majority of species in the genus Echiniscus (Heterotardigrada) have been described based on differences in the chaetotaxy or dorsal sculpture. Dorsal sculpture is, in general, considered to be species-specific and not very variable; however, many problems have arisen due to various interpretations of microscope images, which has led to taxonomic confusion in the genus Echiniscus. Conversely, chaetotaxy is generally much easier to interpret, even using low-quality microscope optics. In this study, we emended the description of Madagascan population of Echiniscus tristis Gasiorek & Kristensen, 2018 that exhibits several different types of chaetotaxy and dorsal sculpture. The analysed specimens were characterised by two types of chaetotaxy, A-C-Dd-E and A-Dd-E, but we also found a wide range of variation in appendage number, shape and length. The observed differences are partly correlated with life stages. Additionally, we analysed DNA sequences of 28S rRNA, ITS-2 and COI of the two main morphotypes, and did not find significant genetic differentiation of the two morphotypes. This highlights the importance of analysing the morphology of both immature stages and adults, as well as of DNA markers in tardigrade species identification.