Search

Tardigrade taxonomy is most often hindered by prevalent outdated species descriptions, lack of integrative redescriptions, scarce genetic information, and fragmentary sampling. Here, we diagnose the problems obscuring phylogenetic inference and the taxonomy of the cosmopolitan family Ramazzottiidae. We carried out the most extensive phylogenetic analysis of this family to date, with a considerable influx of new genetic data from poorly sampled regions of the world. We found two new distinct evolutionary lineages defined by distinct morphological traits (dorsal cuticular sculpturing and/or body shape), characterized by restricted geographic distributions, and we delineated them as new species complexes: the Neotropical Ramazzottius baumanni complex and the Afro-Oriental Ramazzottius szeptyckii complex. Nevertheless, we could not confidently ascertain the taxonomic status of both complexes due to: (i) the current state of the ramazzottiid taxonomy, with outdated and/or imprecise species descriptions with heterogeneous terminology and, in many cases, without accounting for intraspecific variation; (ii) the missing genetic information for key taxa; and (iii) the possible lack of monophyly of Cryoconicus and Ramazzottius as suggested by our results. In addition to diagnosing the problems of ramazzottiid phylogeny and systematics, we also propose possible solutions that could accelerate the progress in our understanding of the evolution of this group. [ABSTRACT FROM AUTHOR]

Green, brown and black pigments are uncommon in the otherwise typically yellow to orange Echiniscidae. Viridiscus , a genus currently represented by a handful of species, in which cuticular coloration varies from a light green through dark green to almost black, has been an exception. Here, we uncover a new echiniscid lineage from the primeval subtropical and tropical rainforests of India and Tanzania, comprising three species with a caramel/brown body. Given that both Viridiscus and the new species complex lack dorsolateral trunk appendages and share dark cuticular pigmentation, they may be mistaken for each other. However, a closer inspection of the dorsal cuticular sculpture and molecular phylogenetic analyses indicate that the new complex belongs within the Echiniscus spinulosus morphogroup. Thus, the presence of dark pigments in two indirectly related lineages is evidence for the convergence of dark cuticular coloration in limno-terrestrial heterotardigrades. We detected three species in the new complex: Echiniscus brunus sp. nov. from the Western Ghats (Tamil Nadu, India), and two other candidate species, Echiniscus aff. brunus sp. can. 1 and Echiniscus aff. brunus sp. can. 2, from India and Tanzania, respectively. We refrain from describing the two latter species formally because they exhibit little or no morphological differences, which is yet another clear case of the crucial role of DNA barcoding in an accurate estimation of tardigrade species richness. [ABSTRACT FROM AUTHOR]

Numerous evolutionary lineages representing an armoured, limno-terrestrial family Echiniscidae are restricted to high mountainous or polar localities, exhibiting clear cold stenothermic preferences. One such group is the genus Claxtonia , with its type species Claxtonia wendti , originally described from Svalbard and later on reported globally. In this paper, we re-describe this taxon by establishing the neotype from Spitsbergen. We sequenced five genetic markers (18S rRNA, 28S rRNA, ITS-1, ITS-2, and COI) for multiple populations of Claxtonia , including C. mauccii , C. molluscorum , C. wendti , and several potentially new species, collected in the Alps, Andes, Carpathians, Scotland, Iceland, Southern Appalachians, Spitsbergen, Scandinavian Peninsula, Borneo, and the West Indies. The relationships between these species are elucidated thanks to the phylogenetic reconstructions based on nuclear loci. Various Claxtonia species frequently co-occur in mosses and lichens, which hampers delineating their probable geographic ranges. All historical records of C. wendti are questioned in the light of our revision. Delineation of new species within the genus is nipped in the bud due to numerous problems with original species descriptions, unknown intraspecific (including ontogenetic) variability, and the lack of DNA barcodes. Finally, it is hypothesized that Claxtonia potentially comprises two lineages: a cold-stenothermic one and a thermophilic subtropical–tropical one. [ABSTRACT FROM AUTHOR]

The recent integrative revision of the family Macrobiotidae demonstrated monophyly of the genus Macrobiotus and its complex, mosaic morphological evolution. Here, we analyse three Macrobiotus populations that exhibit extraordinary claw morphology characterized by elongated primary branches. Two of these populations, from the Arctic, were initially classified as Macrobiotus ariekammensis , but detailed integrative analyses resulted in splitting them into two subspecies: Macrobiotus ariekammensis ariekammensis and Macrobiotus ariekammensis groenlandicus subsp. nov.. The third population was Macrobiotus kirghizicus from Kyrgyzstan. Given the unusual phenotype of the above-mentioned taxa, we tested whether they constitute a distinct lineage in the family Macrobiotidae and could be delineated as a new genus. Although the phylogenetic investigation showed that the three taxa form a monophyletic group, the clade is nested in the genus Macrobiotus. Therefore, despite their morphological distinctiveness, a new genus cannot be established and we group these taxa in the Macrobiotus ariekammensis species complex instead. The complex includes the three above-mentioned taxa and Macrobiotus ramoli , which is included based on morphological characters. Moreover, our results provide evidence for rapid parallel evolution of long claws in macrobiotid tardigrades inhabiting cold and icy environments. Finally, we discuss the validity of the recent suppression of the genus Xerobiotus , which gathers macrobiotids with reduced claws. [ABSTRACT FROM AUTHOR]

The genus Barbaria , recently established to accommodate the former Echiniscus bigranulatus group, is a tardigrade group emblematic for the South American tardigrade fauna. This unappendaged echiniscid lineage is widely recognized for the so-called 'double' sculpturing composed of endocuticular pillars and pseudopores or pores in the dorsal cuticle. The phylogenetic relationships in the genus have so far been completely unknown, but the discovery of two new species (B. paucigranulata sp. nov. and B. weglarskae sp. nov.), together with new genetic data for further six species (B. bigranulata , B. charrua comb. nov. , B. danieli , B. jenningsi , B. madonnae and B. ollantaytamboensis), create an opportunity not only to uncover phyletic relationships, but also to reconstruct morphological evolution in the genus. To achieve this, we sequenced five genetic markers (18S rRNA, 28S rRNA, ITS1, ITS2, COI) for multiple populations of eight species of Barbaria (two-thirds of all known species) collected in Alabama (USA), Argentina and the Antarctic, and we analysed them in tandem with detailed morphological data. Our phylogentic analysis and the reconstruction of evolution of morphological traits suggests that the ancestor of the genus inhabited the Neotropics, and it was morphologically most similar to B. bigranulata. We also analyse literature records of Barbaria and conclude that the genus is most likely limited to the Neotropics, Antarctica and southern parts of the Nearctic. The findings are discussed in the context of the phylogeny of the Echiniscus evolutionary line. [ABSTRACT FROM AUTHOR]

One of the most extensive species radiations in the tardigrade evolution took place in the Echiniscus phylogenetic line, which contains the genus Echiniscus with over 120 species described to date. The internal classification of Echiniscus is historically based on two major sources of variability: chaetotaxy, that is the arrangement and the shape of trunk appendages, and the sculpturing of dorsal plates. These two criteria allowed for the delineation of species complexes, such as the blumi-canadensis or the spinulosus group. Recent phylogenetic analyses confirmed that they represent monophyletic lineages. However, the affinities of some species that have not been sequenced are not straightforward given their uncommon morphologies. In this paper, we present five Echiniscus species found in Argentina, two of which constitute such exemplary cases. Echiniscus aonikenk sp. nov. exhibits extraordinarily elongated cirri A , exceeding 50% of the body length, and dorsoventrally flattened trunk spines, including particularly wide spines E. The species is a probable sister group of the spinulosus complex. Furthermore, Echiniscus evelinae de Barros, 1942, reported here only third time ever, is characterised by an extreme elongation of cirri E , often exceeding the body length, and by autapomorphic dorsal sculpturing comprising epicuticular granules, pseudopores, distinct endocuticular reticulum and pillars. Analogously to E. aonikenk sp. nov. , E. evelinae apparently constitutes a separate evolutionary lineage. Finally, Echiniscus pellucidus sp. nov. (the merokensis complex), Echiniscus peruvianus Binda & Pilato, 1994 syn. nov. (the testudo complex) and Echiniscus manuelae da Cunha & do Nascimento Ribeiro, 1962 (the spinulosus complex) are analysed. Morphological peculiarities revealed in this study are discussed in the light of the Echiniscus taxonomy. [ABSTRACT FROM AUTHOR]

Incomplete descriptions of nominal taxa are one of the most significant obstacles in modern taxonomy, including the taxonomy of Tardigrada. Another major problem in tardigrade systematics is the lack of tests for the reliability of genetic markers in species delineation. Here, we employ an integrative taxonomy approach to redescribe the nominal taxon for the P. areolatus complex, Paramacrobiotus areolatus. Moreover, we obtained multilocus DNA sequences for another 16 populations representing 9–12 Paramacrobiotus species collected from Europe, North America, Africa and Australia, enabling us to reconstruct the most extensive phylogeny of the genus to date. The identification of a pair of potentially cryptic dioecious P. areolatus complex species with divergent genetic distances in ITS2 (1.4%) and COI (13.8%) provided an opportunity to test the biological species concept for the first time in the history of tardigrade taxonomy. Intra- and interpopulation crosses did not differ in reproductive success in terms of F1 offspring. However, because of the low F1 family sizes, we were unfortunately unable to test F1 hybrid fertility. Although our results are only partially conclusive, they offer a baseline not only for further taxonomic and phylogenetic research on the areolatus complex, but also for studies on species delineation in tardigrades in general. [ABSTRACT FROM AUTHOR]

The interplay between tardigrade genetic and ontogenetic diversity, resulting in morphological variation within a species, remains a poorly studied field. In this work, by combining qualitative (light and scanning electron microscopy), quantitative (morphometrics) and genetic analyses (DNA sequencing of five molecular markers) on five Palearctic populations of Nebularmis reticulatus (Murray, 1905) and a Tanzanian population of Nebularmis cirinoi (Binda and Pilato, 1993), all rare members of the Echiniscidae, we discuss intra- and interspecific variability in limno-terrestrial Heterotardigrada. We show that in these parthenogenetic (thelytokous) echiniscid species: (a) morphology strongly varies among life stages and between populations; (b) between populations of a single species there are statistically significant differences in the lengths of sclerotised structures commonly used in species delineation; (c) populations are dominated by one or two haplotypes of quickly evolving DNA fragments (ITS-1, ITS-2, COI), which suggests that such populations are characterised by low genetic diversity. Additionally, here we establish Loch Ness (Scotland) as the neotype locality for N. reticulatus. Finally, challenges of the taxonomy of the genus Nebularmis Gąsiorek & Michalczyk, 2019 are highlighted. [ABSTRACT FROM AUTHOR]

In this article we describe a newParamacrobiotusspecies of theareolatusgroup by means of integrative taxonomy. Together with the detailed morphological and morphometric data (obtained from light and scanning electron microscopy) we also provide DNA sequences of four universal molecular markers used in tardigrade taxonomy (three nDNA fragments: 18S rRNA, 28S rRNA, ITS-2, and one mtDNA fragment: COI). The animals ofParamacrobiotus lachowskaesp. nov. are similar to several species of theareolatuscomplex and the eggshell ornamentation is similar to that of two species of therichtersigroup. Therefore, the new species can be easily distinguished from theareolatusgroup species by egg morphology (dome-like, wrinkled processes with long flexible spines/filaments covered by fine short hairs) and from species of therichtersicomplex by the absence of the microplacoid.Paramacrobiotus lachowskaesp. nov. is the 43rd species reported from Colombia and fifthParamacrobiotusspecies from this South American country. http://zoobank.org/urn:lsid:zoobank.org:pub:FEDC11D3-DCCF-4699-A704-CE6DEA1CDED4 [ABSTRACT FROM AUTHOR]

The Philippines is considered a country with high biodiversity and endemism. However, the status of its tardigrade fauna is still practically unknown. In this study, a limnoterrestrial eutardigrade, Mesobiotus insanis, new species, from Diliman, Quezon City, located on the largest island in the Philippine Archipelago is described. Integrative taxonomy, via the combined morphological and morphometric analyses (imaging via phase contrast [PCM] and scanning electron microscopy [SEM]) aided with a molecular analysis (DNA barcoding of the 18S rRNA, 28S rRNA, ITS-2, and COI markers), was employed to verify the status of the population as a new species. Mesobiotus insanis, new species, differs from its congeners mainly by its unique egg morphology characterised by an exceptionally complex sculpturing of the eggshell areolae in addition to other morphometric characters. The molecular analysis showed that the new species is genetically closest to Mesobiotus philippinicus Mapalo, Stec, Mirano-Bascos & Michalczyk, 2016, recently described also from the Philippines. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phylogenetic analysis recovered monophyly of the tardigrade genus Macrobiotus. • New evolutonaly distinct group is erected to the genus level (Sisubiotus gen. nov.) • The genus Xerobiotus is deeply nested within Macrobiotus and thus suppressed. • Distinct species complexes within Macrobiotus are delineated. • Demonstration of complex phenotypic evolution within the family Macrobiotidae. The family Macrobiotidae is one of the most speciose and diverse groups among tardigrades. Although there have been attempts to reconstruct the phylogeny of this family, the evolutionary relationships within Macrobiotidae are only superficially determined as available genetic data cover only a small fraction of this vast group. Here, we present the first extensive molecular phylogeny of the family based on four molecular markers (18S rRNA, 28Sr RNA, ITS-2 and COI) associated with detailed morphological data for the majority of taxa. The phylogenetic analysis includes nearly two hundred sequences representing more than sixty species, including sixteen taxa that have never been sequenced and/or analysed phylogenetically before. Our results recovered a new monophyletic group, comprising Macrobiotus spectabilis Thulin, 1928 and Macrobiotus grandis Richters, 1911, for which we erect a new genus, Sisubiotus gen. nov. , to accommodate its evolutionary distinctiveness. The largest, so far, dataset for the family Macrobiotidae showed that the genus Xerobiotus is nested within the clade representing the genus Macrobiotus deeper than it was earlier assumed, therefore we propose to suppress Xerobiotus and transfer its species to Macrobiotus. Moreover, mapping key morphological traits onto macrobiotid phylogeny exposed complex evolution of phenotypes within the Macrobiotus hufelandi group, i.e. Macrobiotus s.s. Finally, our findings enabled a detailed revision and discussion on species compositions of the most ubiquitous tardigrade genera, species groups and species complexes, which resulted in changes of taxonomic statuses of a number of macrobiotid species. All this contributes to the reconstruction of the morphological evolution within Macrobiotidae. [ABSTRACT FROM AUTHOR]