Integrative description of a new Dactylobiotus (Eutardigrada: Parachela) from Antarctica that reveals an intraspecific variation in tardigrade egg morphology

Homology of the head sensory structures between Heterotardigrada and Eutardigrada supported in a new species of water bear (Ramazzottiidae: Ramazzottius)

Phylum Tardigrada is represented by microscopic eight-legged panarthropods that inhabit terrestrial and marine environments. Although tardigrades are emerging model animals for areas of research including physiology, evolutionary biology, and astrobiology, knowledge of their external morphology remains insufficient. For instance, homologies between marine and terrestrial relatives largely remain unexplored. In the present study we provide detailed pictures of the head sensory organs in a new tardigrade, Ramazzottius groenlandensis sp. nov. Specimens were collected from a mixed moss and lichen sample on Ella Island, East Greenland. The new species differs from congeneric species in the presence of polygonal sculpturing on the dorsal cuticle, which is accentuated in the posterior region of the body, a lateral papilla on leg IV, and distinctive egg morphology. A Bayesian phylogenetic analysis (18S rRNA + 28S rRNA + COI) places the new species within the genus Ramazzottius with high confidence. Interestingly, the new species shows a full set of well-developed cephalic organs, which correspond to all sensory fields found in eutardigrades. Details on the full set of head organs were present only for heterotardigrades. The surface of these organs is covered with small pores, which presumably play a sensory role. This discovery suggests the homology of head sensory structures between heterotardigrades and eutardigrades, implying that the distinctive arrangement and positioning of sensory organs on the head is a plesiomorphic feature of tardigrades. Moreover, we find that the Ramazzottius oberhaeuseri morphotype forms a morphogroup, not a monophyletic species complex.

Morphological and genetic variability in cosmopolitan tardigrade species-Paramacrobiotus fairbanksi Schill, Förster, Dandekar & Wolf, 2010

Paramacrobiotus fairbanksi was described from Alaska (USA) based on integrative taxonomy and later reported from various geographical localities making it a true cosmopolitan species. The 'Everything is Everywhere' (EiE) hypothesis assumes that the geographic distribution of microscopic organisms is not limited by dispersal but by local environmental conditions, making them potentially cosmopolitan. In the present work we report four new populations of P. fairbanksi from the Northern Hemisphere which suggests that the 'EiE' hypothesis is true, at least for some tardigrade species. We also compared all known populations of P. fairbanksi at the genetic and morphological levels. The p-distances between COI haplotypes of all sequenced P. fairbanksi populations from Albania, Antarctica, Canada, Italy, Madeira, Mongolia, Spain, USA and Poland ranged from 0.002 to 0.005%. In total, twelve haplotypes (H1-H12) of COI gene fragments were identified. We also report statistically significant morphometrical differences of species even though they were cultured and bred in the same laboratory conditions. Furthermore, we also discuss differences in the potential distribution of two Paramacrobiotus species.

Reaching the Monophyly: Re-Evaluation of the Enigmatic Species Tenuibiotus hyperonyx (Maucci, 1983) and the Genus Tenuibiotus (Eutardigrada)

Revisions and redescriptions of taxa described in the past and that are now categorized as insufficiently diagnosed often play a crucial role in making further progress in modern taxonomy in many groups of organisms. Here we revised an enigmatic tardigrade species Tenuibiotus hyperonyx (Maucci, 1983) based on the newly discovered topotypic population from the Italian Alps. We performed an integrative analysis of morphological and genetic data in order to present an upgraded species description and elucidate its phylogenetic position. Our results enabled us to confidently place T.hyperonyx within the family Richtersiusidae, as a member of the genus Diaforobiotus. This change, together with a re-assessment of microphotographs of the Tenuibiotus willardi (Pilato, 1977) and Tenuibiotus bozhkae Pilato, Kiosya, Lisi, Inshina & Biserov, 2011 types, led to the discussion on species composition with narrative taxa amendments for the taxonomic parties involved in the proposed alteration.

The largest moss carpet transplant in Antarctica and its bryosphere cryptic biodiversity

As part of the reconstruction of the Brazilian Antarctic Station on King George Island, three areas of moss carpet were transplanted to minimize the impact of the new facilities on the local biodiversity. A total of 650 m² of moss carpet was transplanted to neighboring but previously uncolonized locations and has subsequently survived for the last 3 years. Antarctic moss carpets typically comprise low moss species diversity and are often monospecific. We investigated the cryptic biodiversity that was transplanted along with the carpets using a metabarcoding approach through high throughput sequencing. We targeted 16S rRNA for Bacteria and Archaea, ITS for Fungi and Viridiplantae and Cox1 for Metazoa. We detected DNA representing 263 taxa from five Kingdoms (Chromista, Fungi, Metazoa, Protista and Viridiplantae), two Domains (Archaea and Bacteria) and 33 Phyla associated with the carpet. This diversity included one Archaea, 189 Bacteria, 24 Chromista, 19 Fungi, eight Metazoa, seven Protista and 16 Viridiplantae. Bacteria was the most abundant, rich and diverse group, with Chromista second in diversity and richness. Metazoa was less diverse but second highest in dominance. This is the first study to attempt transplanting a significant area of moss carpet to minimize anthropogenic environmental damage in Antarctica and to use metabarcoding as a proxy to assess diversity associated with Antarctic moss carpets, further highlighting the importance of such habitats for other organisms and their importance for conservation.

Resolving the systematics of Richtersiidae by multilocus phylogeny and an integrative redescription of the nominal species for the genus Crenubiotus (Tardigrada)

The family Richtersiidae, although established recently with the use of phylogenetic methods, was considered potentially paraphyletic at the time of its erection. Until now, the family comprised four genera, Richtersius, Diaforobiotus, Adorybiotus and a newly erected genus Crenubiotus. However, the genetic characterisation for the latter two genera was very limited or absent. To address concerns about the phylogenetic affinity of these two genera, we present a multilocus phylogeny of the families Richtersiidae and Murrayidae based on four molecular markers (18S rRNA, 28S rRNA, ITS-2 and COI). Our results show a distinct evolutionary lineage composed of Adorybiotus and Crenubiotus, which is sister to Murrayidae. In order to accommodate the phylogenetic and morphological distinctiveness of this lineage, we erect a new family, Adorybiotidae fam. nov. The new taxon differs morphologically from other families in the superfamily Macrobiotoidea by a unique combination of traits: (1) the presence of tubercles/cushions with aggregations of microgranules on their surfaces present on all legs and on the dorso-caudal cuticle, (2) a system of internal septa in claws, and (3) buccal apparatus morphology. Moreover, in order to stabilise the taxonomy and nomenclature in the genus Crenubiotus, we redescribe its type species, Crenubiotus crenulatus, by means of integrative taxonomy and designate a new neotype based on a population from the original terra typica.