For many years, Paramacrobiotus richtersi was reported to consist of populations with different chromosome numbers and reproductive modes. To clarify the relationships among different populations, the type locality of the species (Clare Island, Ireland) and several Italian localities were sampled. Populations were investigated with an integrated approach, using morphological (LM, CLSM, SEM), morphometric, karyological, and molecular (18S rRNA, cox1 genes) data. Paramacrobiotus richtersi was redescribed and a neotype designed from the Irish bisexual population. Animals of all populations had very similar qualitative and quantitative characters, apart from the absence of males and the presence of triploidy in some of them, whereas some differences were recorded in the egg shell. All populations examined had the same 18S haplotype, while 21 haplotypes were found in the cox1 gene. In four cases, those qualitative characters were correlated with clear molecular (cox1) differences (genetic distance 14.6–21.8%). The integrative approach, which considered the morphological differences in the eggs, the reproductive biology and the wide genetic distances among putative species, led to the description of four new species (Paramacrobiotus arduus sp. n., Paramacrobiotus celsus sp. n., Paramacrobiotus depressus sp. n., Paramacrobiotus spatialis sp. n.) and two Unconfirmed Candidate Species (UCS) within the P. richtersi complex. Paramacrobiotus fairbanksi, the only ascertained parthenogenetic, triploid species, was redescribed and showed a wide distribution (Italy, Spain, Poland, Alaska), while the amphimictic species showed limited distributions. The difference in distribution between apomictic and amphimictic populations can be explained by the difference in the dispersal potentials associated with these two types of reproduction.

The Tardigrade Resistance to Space Effects (TARSE) project, part of the mission LIFE on FOTON-M3, analyzed the effects of the space environment on desiccated and active tardigrades. Four experiments were conducted in which the eutardigrade Macrobiotus richtersi was used as a model species. Desiccated (in leaf litter or on paper) and hydrated tardigrades (fed or starved) were flown on FOTON-M3 for 12 days in September 2007, which, for the first time, allowed for a comparison of the effects of the space environment on desiccated and on active animals. In this paper, we report the experimental design of the TARSE project and data on tardigrade survival. In addition, data on survival, genomic DNA integrity, Hsp70 and Hsp90 expressions, antioxidant enzyme contents and activities, and life history traits were compared between hydrated starved tardigrades flown in space and those maintained on Earth as a control. Microgravity and radiation had no effect on survival or DNA integrity of active tardigrades. Hsp expressions between the animals in space and the control animals on Earth were similar. Spaceflight induced an increase of glutathione content and its related enzymatic activities. Catalase and superoxide dismutase decreased with spaceflight, and thiobarbituric acid reactive substances did not change. During the flight mission, tardigrades molted, and females laid eggs. Several eggs hatched, and the newborns exhibited normal morphology and behavior. Key Words: Tardigrada—TARSE experiment—FOTON-M3 mission—Survival—DNA—Heat shock proteins—Antioxidant enzymes—Life history traits. Astrobiology 9, 581–591.

Tardigrades represent one of the most abundant groups of Antarctic metazoans in terms of abundance and diversity, thanks to their ability to withstand desiccation and freezing; however, their biodiversity is underestimated. Antarctic tardigrades from Dronning Maud Land and Victoria Land were analysed from a morphological point of view with light microscopy and scanning electron microscopy, and from a molecular point of view using two genes (18S, 28S) analysed in Bayesian inference and maximum-likelihood frameworks. In addition, indel-coding datasets were used for the first time to infer tardigrade phylogenies. We also compared Antarctic specimens with those from Italy and Greenland. A combined morphological and molecular analysis led to the identification of two new evolutionary lineages, for which we here erect the new genera Acanthechiniscus, gen. nov. (Echiniscidae, Echiniscoidea) and Mesobiotus, gen. nov. (Macrobiotidae, Macrobiotoidea). Moreover, two species new to science were discovered: Pseudechiniscus titianae, sp. nov. (Echiniscidae : Echiniscoidea) and Mesobiotus hilariae, sp. nov. (Macrobiotidae : Macrobiotoidea). This study highlights the high tardigrade diversity in Antarctica and the importance of an integrated approach in faunal and taxonomic studies. http://zoobank.org/urn:lsid:zoobank.org:pub:8AAB42BF-B781-4418-A385-DC80C18EC31D

So far, most studies on tardigrade resistance to extreme stresses have focused on their responses to several chemical and physical extremes, but there is still a paucity of data regarding the tardigrade responses to ultraviolet radiation. Considering also the future perspectives offered by space flights, we compared the biological responses of two eutardigrade species (Paramacrobiotus richtersi and Ramazzottius oberhaeuseri) to UV irradiation, alone or in combination with multiple stressors (temperature and air relative humidity) in two different physiological conditions (desiccated and hydrated states). Tardigrades were exposed to seven different UV doses (from 10.32 up to 87.72 kJ m-2) in a controlled climatic chamber. The results showed that active and anhydrobiotic tardigrades were able to withstand high doses of ultraviolet radiations. The survival rate of hydrated or desiccated specimens of both species was inversely related to the UV doses, with P. richtersi that better tolerated the increase of UV dose than R. oberhaeuseri. Surprising, the tolerance to physical and chemical extreme stresses is not an exclusive property of desiccated tardigrades; in certain environmental conditions (high air humidity level or low temperature) desiccated tardigrades have a lower or similar withstanding to UV irradiation than hydrated ones. This represents a further demonstration of the uniqueness of this animal group in tolerating extreme stresses. In addition, we demonstrated that high temperatures have a strong impact on tardigrade survival during UV exposition both in hydrated and desiccated animals

Important contributions have been made to the systematics of Eutardigrada in recent years, but these have also revealed that several taxa are polyphyl