Paramacrobiotus species has been described from almost every corner of the world. To date 45 species have been reported from this genus. The species’ presence in different climatic conditions and habitat provides evidence of their adaptation to various harsh environments. In this review, we provide a concise summary of changes observed due to various cryptobiotic conditions in many species of this genus, geographical distribution of all the species, feeding behaviour, life history, microbiome community, Wolbachia endosymbiont identification, reproduction, phylogeny and general taxonomy of the species from genus Paramacrobiotus. Furthermore, we provide a new diagnostic key to the genus Paramacrobiotus based on the morphological and morphometric characters of adults and eggs.

The Ramazzottius varieornatus tardigrade is an extremotolerant terrestrial invertebrate belonging to the phylum of Tardigrada. At a length of 0.1-1.0 mm, tardigrades are small animals with an exceptional tolerance to extreme conditions such as high pressure, chemicals and irradia-tion. These properties have been attributed to the recently-discovered Dsup protein. Dsup is a nucleosome-binding protein that prevents DNA damage against X-ray and oxidative stress without impairing cell life, also in Dsup-transfected animal and plant cells. However, the precise “protective” role of this protein is still under study. We performed experiments on human cells and shows that, as compared to control cells, Dsup+ cells are more resistant to UV-C exposure and H2O2. Real-time PCR identified different expression patterns of endogenous genes involved in apoptosis, cell survival and DNA damage repair in Dsup+ cells in response to H2O2 and UV-C. While H2O2 treatment in Dsup+ cells only marginally involved the activation of pathways responsible for DNA repair reinforcing the idea of a direct protective effect of the protein on DNA, in UV-C exposed cells, Dsup efficiently upregulates DNA damage repair genes. In conclusion, our data may help to delineate the different mechanisms by which the Dsup protein operates in response to different insults.