<p>Tardigrade phylogenetic systematic analyses have been conducted using morphological and molecular data; however, incongruencies between results obtained independently with the data types have been found. This thesis contains new morphological and molecular phylogenetic systematic analyses of tardigrades at the family level, building on previous research. The first part involves morphological data, the second part involves molecular data, and the third part involves combined morphological and molecular data. The morphological data include 50 characters for 15 tardigrade families. The molecular data include updated 18S rRNA, 28S rRNA, and COI gene sequences, in two sets; the first set provides the most-extensive representation of tardigrade families and comprises 18S rRNA sequences; the second set provides the most-complete representation of molecular data per species, where available, and involves the concatenation of 18S rRNA, 28S rRNA, and COI gene sequences. Finally, the combined data involves a supermatrix containing morphological and molecular data. The analyses are used to test results from previous systematics research and to contribute more information to tardigrade systematics.</p> / Master of Science (MSc)

Screening of a deeply sequenced transcriptome using Illumina sequencing as well as the genome of the tardigrade Hypsibius dujardini revealed a set of five opsin genes. To clarify the phylogenetic position of these genes and to elucidate the evolutionary history of opsins in Panarthropoda (Onychophora + Tardigrada + Arthropoda), we reconstructed the phylogeny of broadly sampled metazoan opsin genes using maximum likelihood and Bayesian inference methods in conjunction with carefully selected substitution models. According to our findings, the opsin repertoire of H. dujardini comprises representatives of all three major bilaterian opsin clades, including one r-opsin, three c-opsins, and a Group 4 opsin (neuropsin/opsin-5). The identification of the tardigrade ortholog of neuropsin/opsin-5 is the first record of this opsin type in a protostome, but our screening of available metazoan genomes revealed that it is also present in other protostomes. Our opsin phylogeny further suggests that two r-opsins, including an "arthropsin", were present in the last common ancestor of Panarthropoda. While both r-opsin lineages were retained in Onychophora and Arthropoda, the "arthropsin" was lost in Tardigrada. The single (most likely visual) r-opsin found in H. dujardini supports the hypothesis of monochromatic vision in the panarthropod ancestor, whereas two duplications of the ancestral panarthropod c-opsin have led to three c-opsins in tardigrades. Although the early-branching nodes are unstable within the metazoans, our findings suggest that the last common ancestor of Bilateria possessed six opsins: two r-opsins, one c-opsin, and three Group 4 opsins, one of which (Go opsin) was lost in the ecdysozoan lineage.

The main subject of my papers has been the phylum Tardigrada, with particular emphasis on the Antarctic fauna. While this is one of the ‘lesser known phyla’ the group forms an important element of Antarctic non-marine ecosystems. My work has centred on four interrelated themes: i) taxonomy, predominantly Tardigrada and with an Antarctic bias though including wider global species and high taxon groupings (I have also worked on other taxa such as Fungi-imperfecti and freshwater invertebrates); ii) biodiversity of tardigrades, particularly Antarctic habitats; iii) data-based studies based on the terrestrial Tardigrada and Antarctic freshwater crustaceans; and iv) biogeographic analysis of these databases. The thesis presented consists of papers published in major, peer-reviewed journals, along with book chapters published and in press. Several of my papers have been cited 10-30 times according to the ISI Web of Science citation system. Highlights of my work include being the first to publish a paper on the global terrestrial biogeography of a phylum and showing the extant limno-terrestrial tardigrade fauna reflect the early tectonic break-up of the Laurasia, West and East Gondwana super continents between 65 and 135 million years ago.

Tardigrades can handle extreme conditions such as heat, cold and drought, thanks to a process called cryptobiosis which can be found in a limited amount of taxa on Earth. More knowledge about such animals may help us to understand the potential and limitations of life both on Earth and possibly in space. Such knowledge may also help develop novel, useful applications for the society, such as better storage of sensitive medicine. However, our knowledge about tardigrades is limited. We know little about their distribution and diversity, especially in Sweden, and above all in northern Sweden. The aim of this study was threefold; i) to explore the biogeography of the tardigrades based on molecular data; ii) to screen for tardigrades in Umeå by examining moss samples from different locations; and iii) to explore some of the associates of tardigrades in moss (such as bacteria and micro- and meiofauna). The biogeography was explored by collecting all published ribosomal gene sequences (the small subunit 18S rRNA) from the Silva gene database. These sequences were used for plotting the locations from which these gene sequences had been retrieved on a world map and the correlation between gene sequence, country and biotope was examined. The tardigrade groups most sequenced are Macrobiotus, Ramazottius and Echiniscus, and the milieu most studied seems to be different types of soil. Other investigated isolation sources are drinking water, cryconite and church walls. However, much remains to be further explored. For example, the world map showed that the only molecular data on Swedish tardigrades have been retrieved from Öland. In the lab, tardigrades were found in some of the moss samples, together with other micro- and meiofauna. Three groups of bacteria (Betaproteobacteria, Gammaproteobacteria and Firmicutes) could be identified in one of the investigated mosses. These results suggest that tardigrades live in a diverse environment with different types of organisms both on the microbial as well as on the micro-meio-fauna level.

Five marine arthrotardigrade species are recorded from Moorea, Society Islands, French Polynesia. Four were collected from coral sand; two, Dipodarctus anaholiensis Pollock, 1995 and Florarctus kwoni Chang & Rho, 1997, are new records for the region, and two, Halechiniscus perfectus Schulz, 1955 and Styraconyx kristenseni kristenseni Renaud-Mornant, 1981, have been previously reported. The fifth, a new species Styraconyx turbinarium sp. nov., is described and was collected from the drifting brown alga Turbinaria ornata. The new species is characterized by the presence of peduncles on all digits, an elongate primary clava, and the lateral cirrus A arising from a common pedestal and enveloped by a common membrane extending almost to the claval tip. The new species differs from the most similar species, Styraconyx tyrrhenus D'Addabbo Gallo, Morone De Lucia & de Zio Grimaldi, 1989, by having longer and differently shaped primary clavae which are elongated in the new species and club-shaped in S. tyrrhenus. By having a dorsal cuticle that is coarsely punctated but without folds or other ornamentations, the new species can be easily distinguished from S. craticulus (Pollock, 1983), a species with similar primary clavae, but with cuticular dorsal folds ornamented with a grid-like pattern.

Quantitative traits are an important part of tardigrade taxonomy for both heterotardigrades and eutardigrades. Because most quantitative traits vary as a function of body size, variation in body size complicates comparisons between individuals or populations. Thus, body size effects must be eliminated in morphometric analysis. Although ratios (size of character/body size) are often used to attempt this, they only work for the specific case of isometry (i.e. when a structure grows proportionally to body size). Ratios do not eliminate body size effects for allometric (disproportionate) growth. In eutardigrades, body size is highly correlated with the length of the rigid buccal tube, whereas body length (BL) is highly variable because of the flexibility of the cuticle and the orientation and coverslip pressure on the specimen. In heterotardigrades, BL is typically used to indicate body size because the thickened dorsal plates provide more rigidity and reliability in measurements. We measured 27 traits in 97 specimens of Paramacrobiotus tonollii (Eutardigrada) and 14 traits in 100 specimens of Echiniscus virginicus (Heterotardigrada) and found that many traits are allometric rather than isometric. Thorpe (1975, Biol J Linn Soc 7:27) provided a normalization technique to eliminate body size effects for any trait regardless of its relationship to body size. Using the data from P. tonollii, we show that Thorpe's size normalization does successfully remove buccal tube length effects (body size effects), while pt indices generally do not. We also demonstrate the effectiveness of Thorpe's normalization in species delineations of Macrobiotus recens and Macrobiotus hufelandi, two species that differ primarily in a few quantitative traits and overall body size in addition to the eggs. Based on these examples, we propose that the allometric exponent (b) and the Y-intercept (a*) of the regression of Thorpe normalized traits versus body size are valuable metrics in tardigrade systematics.

Samples of moss, lichens, liverworts and leaf litter collected in the Lower and Upper Peninsulas of the state of Michigan, USA, contained 28 species of water bears (phylum Tardigrada). Eighteen species were considered cosmopolitan, widely distributed in several biogeographical regions. One species, Minibiotus jonesorum sp. n., is described and illustrated. This new species is characterized by having ten transverse bands of polygonal pores that increase in size from anterior to posterior, three macroplacoids that increase in size from anterior to posterior and by lacking a microplacoid or leg granulation. The medial and posterior pores of M. jonesorum sp. n. are polygonal and much larger than the trefoil pores of M. furcatus, the most similar species in the genus.

A new eutardigrade, Doryphoribius smokiensis sp. nov., is described from soil and leaf litter samples collected in the Great Smoky Mountains National Park in Tennessee, USA. The new species differs from two similar species (with two macroplacoids and a sculptured dorsal cuticle without gibbosities) by the presence of a very wide buccal tube (high buccal tube pt ratio: >20.0), absence of enlarged bases of claws, absence of eyes, and other morphological and morphometric characters.

One of the largest inventories of tardigrades ever conducted occurred from 2000 2010 in the Great Smoky Mountains National Park, USA. Over 16,000 specimens were catalogued, 85 species were identified, 11 species new to science were described, and 16 other possible new species await further study. More than 20 papers have resulted from the GSMNP tardigrade inventory, making the Smokies the most thoroughly studied area in North America for tardigrades. Several species lists have been published over this 20-year period, but many taxonomic revisions and new identifications have led to significant changes to the list. Biogeographical studies citing species records from earlier studies could yield serious errors. Here we update the species list from the Smokies to accommodate the many recent changes in tardigrade taxonomy, we re-Analyze some species in light of delineations of cryptic species groups that have occurred recently via integrative taxonomy, and we provide a table of all synonyms that have been used in previous publications. We also make available, for the first time, the Smokies tardigrade database, complete with all locations, elevations, and substrates.

Mainly because of the problems with species delineation, the biogeography of microscopic organisms is notoriously difficult to elucidate. In this contribution, variable nuclear and mitochondrial DNA markers were sequenced from individual specimens representing the Echiniscus virginicus complex that are morphologically indistinguishable under light microscopy (five populations from the temperate Eastern Nearctic and 13 populations from the subtropical and tropical zone). A range of methods was used to dissect components of variability within the complex (Bayesian inference, haplotype networks, Poisson tree processes, automatic barcode gap discovery delineations, principal components analysis and ANOVA). We found deep divergence between the temperate Eastern Nearctic E. virginicus and pantropical Echiniscus lineatus in all three genetic markers. In contrast, intraspecific genetic variation was very low, regardless of the geographical distance between the populations. Moreover, for the first time, statistical predictions of tardigrade geographical distributions were modelled. The factor determining the allopatric geographical ranges of deceptively similar species analysed in this study is most likely to be the type of climate. Our study shows that widespread tardigrade species exist, and both geographical distribution modelling and the genetic structure of populations of the pantropical E. lineatus suggest wind-mediated (aeolian) passive long-distance dispersal.