Geonemy, ecology, reproductive biology and morphology of the tardigrade Hypsibius zetlandicus (Eutardigrada: Hypsibiidae) with erection of Borealibius gen. n.

The morphology, biology and geographic distribution of Hypsibius zetlandicus (Murray, 1907) are considered. LM and SEM analyses have been carried out on H. zetlandicus and other two species of Hypsibius, with particular emphasis on the buccal-pharyngeal apparatuses. Some peculiar characteristics of this apparatus in H. zetlandicus lead us to the erection of the new genus Borealibius, to which H. zetlandicus (Borealibius zetlandicus comb. n.) is transferred.In the light of new findings in polar, sub-polar and alpine regions and the available bibliographic references, we evidenced for this species a boreo-alpine distribution. The presence of uncommon phenomena for a tardigrade species have been observed analyzing traits of B. zetlandicus reproductive biology (presence of hermaphroditism and parental cares) and ecology (colonization of very different substrates).