Welcome by the Dean Henrik Jeppesen at the 8th International Symposium on Tardigrada

Mr. Chairman. Distinguished ladies and gentlemen. As Dean of Science it is a great honour on behalf of the University of Copenhagen and the Faculty of Science to welcome all of you here to the 8th International Symposium on Tardigrada. We are especially happy to have you here at the August Krogh Institute (named after our well-known Nobel Prize winner in Physiology), because on September 1st we celebrate the establishment of the Faculty. So coming here and honouring our 150 year anniversary jubilee help us to promote the importance of science in our society. The University was founded in 1479 as a theological catholic school. It broke down in 1530 and was reestablished in 1537 after the reformation. Right from the start in 1479 there was science thought of at the university. Mathematics and Astronomy. And Zoology became a subject over the centuries together with other subjects which are today regarded as science. But only in 1850 did we become an independent Faculty thanks to the effort and progress done by the Danish Chemist H.C. Ørsted.The animals, which you study, are marvellous in the sense that they can survive under severe conditions for centuries. Under extreme dry conditions in Sahara, in extreme cold conditions (they can survive minus 273 °C, or survive in vacuum). This has practical implications for people who need to excuse their scientific interest, for medicine if we can freeze human tissue, or for space study how to survive under extreme conditions. The study of Tardigrada is an important field here at the Institute of Zoology, at the Zoological Museum, and at the University of Roskilde, 30 km west of Copenhagen. Some of our most distinguished zoologists take part in this research. That might be the reason why you have chosen to have the symposium here in Copenhagen. They are doing research on tardigrades in marine areas, and in Greenland on the ice cap. Especially interesting are the studies done in the Ikka Fjord in Greenland, where the unique Ikkaite Tufa columns made of calcium carbonate hexahydrate originating from alkaline cold springs at the bottom of the fjord create very specific environments with nearly brackish conditions in the center and sea water salinity on the outside. And this creates varied conditions for different species of Tardigrada.We also celebrate this year the 50th anniversary of the 2. Galathea expedition which went round the world and specifically looked for deep sea fauna. There are Tardigrades here. It has been interesting to look through the 54 abstracts in the programme and read the names and work places for the 65 participants listed. In English tardigrades are called water bears, in Danish “bjørnedyr” meaning bear animals. I prefer the Danish version, this sounds more like pet bears.The symposium is followed by a field trip to the faculty's research station on Disko in Greenland. In 1994 I arrived on the new research vessel “Porsild” to Disko to deliver the new boat some of you will sail in during the workshop up there. I stayed there some days, and there was this man Professor Reinhardt Møbjerg Kristensen, looking into his microscope. It was fascinating to see the joy which he expressed explaining his animals. His engagement was so impressive and his talk so marvellous. It was really his pet animals he caressed all day and night. If all of you are looking on the water bears with the same fascination and engagement, then this will be one of the most entertaining symposiums ever held. One can fear that you are so engaged that you will forget everything around you, even to listen to the contributions of the others, and to be careful that maybe a new group will be announced.I wish you some very good days here at the Faculty of Science and some very fruitful days. I should like to thank the sponsors of the meeting, The Danish Science Foundation, The Carlsberg Foundation and Dr. Bøje Benzon Foundation. I would like to express my gratitude to the organizing committee for attracting the conference here and making the programme so wide and interesting. I can promise the committee will do all their best to help you all way through. And for those going to Disko — you will have a most splendid experience.I shall ask my colleagues at my own institute, Geography, to arrange some bad weather except on Thursday where you join the excursion. This to prevent you from sneaking away and enjoy the wonders of Copenhagen.By this once again welcome and a wish for a fruitfulconference.     

Tardigrades in Space Research - Past and Future

To survive exposure to space conditions, organisms should have certain characteristics including a high tolerance for freezing, radiation and desiccation. The organisms with the best chance for survival under such conditions are extremophiles, like some species of Bacteria and Archea, Rotifera, several species of Nematoda, some of the arthropods and Tardigrada (water bears). There is no denying that tardigrades are one of the toughest animals on our planet and are the most unique in the extremophiles group. Tardigrada are very small animals (50 to 2,100 μm in length), and they inhabit great number of Earth environments. Ever since it was proven that tardigrades have high resistance to the different kinds of stress factors associated with cosmic journeys, combined with their relatively complex structure and their relative ease of observation, they have become a perfect model organism for space research. This taxon is now the focus of astrobiologists from around the world. Therefore, this paper presents a short review of the space research performed on tardigrades as well as some considerations for further studies.     

Foreword

The Eighth International Symposium on Tardigrada was hosted by the Department of Invertebrate Zoology, Zoological Museum, University of Copenhagen and held at the August Krogh Institute from 30 July to 5 August 2000. There were 65 participants at the symposium. Like its predecessors, the symposium presented oral presentations and posters on a wide variety of tardigradological themes, and several invited speakers gave special keynote lectures about molecular biology, computer cladistics, phylogeny, cryptobiosis and palaeontology. Fifty four abstracts were published in the “Booklet of Abstracts” edited by Jesper G. Hansen. The 41 papers appearing in this special issue of Zoologischer Anzeiger represent most of the contributions presented in Copenhagen. Furthermore, a workshop on Arctic Tardigrades was held at Danish Arctic Station, Qeqertarsuaq, Greenland from, 7 to 18 August 2000. There were 15 participants on this Greenlandic Adventure.     

缓步动物休眠现象研究进展

本文对缓步动物休眠现象的研究历史和现状作了简要的回顾和总结。休眠现象是一个集合名词,指的是缓步动物为克服不利的环境条件而出现的新陈代谢活动减弱甚至暂停的生命状态。最新的观点将其划分为两类,即隐生和滞育。根据导致隐生的环境因子的不同,又可分为低湿隐生、低温隐生、高压隐生、低氧隐生四种形式。滞育包括包囊和休眠卵两种形式。缓步动物的三种休眠状态（桶状、包囊和休眠卵）在其一生中任何一个阶段都能够出现,以度过极端不利的环境,并以此延长生物个体的寿命。总之,休眠现象存缓步动物的生态和进化方面具有不可估量的作用。     

Ovary development in Greenland halibut Reinhardtius hippoglossoides in west Greenland waters

Maturity in adult female Greenland halibut Reinhardtius hippoglossoides was studied in three areas in west Greenland waters: the inshore area in Disko Bay and two offshore areas, Baffin Bay and Davis Strait. The aim was to monitor maturity changes in the inshore fjords of Disko Bay over an extended period from winter to autumn and compare these findings with specimens from Baffin Bay and the presumed spawning area in Davis Strait. A significant difference in maturity level was observed in and between the three areas. In Disko Bay maturity indices increased significantly in August and September both with respect to the gonado‐somatic index ( I _G) and the size in the leading oocyte cohort. In the period February to May no significant changes were observed. Mature ovaries were only observed among fish >80 cm total length and only among a fraction of these large fish. Offshore areas of Baffin Bay, even though poorly sampled, showed similar signs in the maturity indices as in Disko Bay. Relative to Disko Bay and Baffin Bay, female fish in Davis Strait had more progressed maturity indices. Furthermore, almost all fish in Davis Strait showed signs of progressed maturity contrary to Disko and Baffin Bay. A large proportion of the Greenland halibut in Disko and Baffin Bay apparently did not begin the maturation cycle until very late in their life history or were repeat spawners with a multi‐year maturation cycle. These observations could thus support the hypothesis that Greenland halibut have a prolonged adolescent phase. Atresia was highest in the early phases of maturation in Greenland halibut but relatively high levels of atresia were also observed in fish in more advanced maturity phase. The first was ascribed to fecundity regulation while the latter could be linked to the fish's fitness condition but it was not possible to show this with the available condition index.     

A survey of the terrestrial Tardigrada of the Vestfold Hills,Antarctica

A survey of the terrestrial tardigrades inhabiting growths of algae, lichens and mosses in the Vestfold Hills, Antarctica, was carried out at 11 and 35 sites during the austral summers of 1980 and 1982, respectively. In all, 24 species of plants were collected from which four genera and four species of Tardigrada were recovered. A key to the tardigrades of the area is presented. The distribution and associational patterns of the tardigrades are discussed in the context of other studies of antarctic Tardigrada.     

A New Species of Freshwater Tardigrades from Disko Island (Greenland) Increases an Unsolved Paradox in Tardigrade Systematics

During the “Workshop on Arctic tardigrades” at the Danish Arctic Station (Qeqertarsuaq, Disko Island, Greenland) an undescribed species of Dactylobiotus was found in freshwater sediments of the Isunngua spring. We have the honour and pleasure to describe this new taxon that we dedicate to all participants of that symposium, naming the species Dactylobiotus octavi sp. n. The animals appear similar to Dactylobiotus dispar and Dactylobiotus haplonyx with the presence of a very short secondary branch in the claws of the first three pairs of legs, but they differ from these species in the size of claw and buccal tube width. This new species also has peculiar ornamented eggs. The eggshell consists of bowl-like processes, each one surrounded by a band of fine pores. A morphological parsimony analysis to identify phylogenetic relationships among D. octavi sp. n. and the other Dactylobiotus species was performed, obtaining inconclusive results. The discovery of this new species increases an unsolved paradox in tardigrade systematics related to the presence of closely related species which share a very similar morphology of the animals but clearly differ in their egg morphology, while, conversely, there are species belonging to different evolutionary lines that have similar eggs, but very different adult morphology. The finding of D. octavi sp. n. increases the already high number of species found in Disko Island and once again underlines the importance of tardigrades in the biodiversity of the Arctic area.     

Geographic variation in cranial morphology of narwhals (Monodon monoceros) from Greenland and the eastern Canadian Arctic

We analyzed variation in nine non-metric and eight metric variables in the skulls of 132 narwhals (Monodon monoceros) from five localities in Greenland (Inglefield Bredning, Melville Bay, Uummannaq, Disko Bay, and Scoresby Sound) and one in the eastern Canadian Arctic (Eclipse Sound). Metric variables were used to compare the combined Disko Bay and Uummannaq samples with the samples from Inglefield Bredning and Scoresby Sound using three different multivariate techniques for each sex. None of the results were significant. Seven of the non-metric variables were independent of age and sex and were used in comparing samples from the six localities. No differences were found among the four localities in West Greenland, but differences were found in two of the non-metric variables between the combined West Greenland sample and the one from Scoresby Sound. A major shortcoming of the analysis based on metric data was the small sample size from several of the areas, which resulted in low statistical power. Genetic as well as environmental factors could explain the differences detected here between narwhals living along the west and the east coasts of Greenland.     

Structural Studies on Diurodrilus Remane (Diurodrilidae fam.n.), with Description of Diurodrilus westheidei sp.n. from the Arctic Interstitial Meiobenthos,W. Greenland*

Diurodrilus westheidei sp.n. is described in terms of the location of the sensoria, ventral ciliated cells, ciliophores, adhesive toes and a big anal cone. Specimens were collected in mid winter at Disko Island, West Greenland. The ultrastructure of D. subterraneus Remane, collected in the summer at Disko Island and Ystad, Sweden, is discussed with new information on the systematic status of this aberrant genus as indicated by the cuticle, pharyngeal area, ciliophores and the spermatozoa. Diurodrilidae fam.n. is introduced for the genus Diurodrilus, here placed in Polychaeta.     

The Biology of Tardigrades: An Introduction to the 9th International Symposium on Tardigrada*

The 9th International Symposium on Tardigrada took place in Tampa, Florida, USA from 28 July to 1 August 2003. Fifty-four participants representing thirteen countries attended and there were fifty-two presentations of which fourteen were chosen for the publication in these proceedings. Topics include cryptobiosis, ecology, taxonomy and systematics of tardigrades. * This symposiumvolume is dedicated to Nigel Marley (Fig. 4) for his courage and persistence in pursuing research on tardigrades, despite ongoing medical challenges. His optimism and positive attitude are an inspiration to all of us, and his willingness to help other tardigradologists is gratefully acknowledged and appreciated.     

Geographic variation of freeze-tolerance in the earthworm Dendrobaena octaedra

Freeze-tolerance and some of the underlying biochemical defence mechanisms in the earthworm Dendrobaena octaedra was investigated. Survival after slow cooling to -2 degrees C, -4 degrees C, or -6 degrees C was analysed in D. octaedra from three geographic regions representing large differences in winter temperature (Denmark, Finland and Greenland). A large variation in freeze-tolerance between the three populations of D. octaedra was found. Earthworms from the northern populations (Finland and Greenland) tolerated lower temperatures (-6 degrees C) than earthworms from the Danish population (poor survival at -4 degrees C and -2 degrees C). In the Finnish population, freezing led to the production of high concentrations of glucose, which reached values much higher than controls (94 mg g(-1) vs. 2 mg g(-1) dry weight). Other potential cryoprotectants were not elevated after freezing. The Danish and Greenlandic populations had substantially lower mean glucose levels after freezing than the Finnish population (about 15 mg g(-1)). Danish earthworms rapidly frozen did not accumulate glucose, and did not survive freezing at -2 degrees C. Danish earthworms exposed to osmotic stress in Ringer's solutions, containing different concentrations of glycerol, showed significantly elevated glucose levels, but did not survive rapid freezing. It was determined if freezing had an influence on the reproduction of the earthworms. After warming to summer temperatures (15 degrees C), survivors of freezing produced viable cocoons. In a field experiment it was tested if natural acclimatization during autumn and winter months had an effect on freeze-tolerance in the Danish population. There was a significant increase of post-freeze survival during this period. The results of the freezing experiments are discussed in relation to the general ecology of D. octaedra.     

Cold tolerance in Tardigrada from Dronning Maud Land,Antarctica

Survival at low temperatures was studied in three species of Tardigrada from Müihlig-Hofmannfjella, Dronning Maud Land, Antarctica. Both hydrated and dehydrated specimens of Echiniscus jenningsi, Macrobiotus furciger and Diphascon chilenense had high survival rates following exposure to -22°C for ca. 600 days, and dehydrated specimens following 3040 days at this temperature. In hydrated E. jenningsi, mortality increased with the duration of exposure from 7 to 150 days at -80°C, while mortalities of the two other species did not change. Hydrated specimens of all species were rapidly killed at -180°C, but all species exhibited good survivorship in the dehydrated state after 14 days at -180°C. In conclusion, hydrated tardigrades are able to survive extended periods at low temperatures, and dehydrated specimens are even better adapted to survive overwintering on Antarctic nunataks.     

Snapshot of micro-animals and associated biotic and abiotic environmental variables on the edge of the south-west Greenland ice sheet

Microinvertebrates play a role as top consumers on glaciers. In this study we tested what kind of cryoconite material the animals inhabit (mud vs granules) on the edge of the Greenland ice sheet (GrIS) in the south-west. We also tested the links between the densities of micro-fauna in cryoconite material and selected biotic (algae, cyanobacteria, bacterial abundances) and abiotic (water depth, pH, ion content, radionuclides) factors. We collected 33 cryoconite samples. Tardigrada and Rotifera were found in 18 and 61% of samples, respectively. Invertebrates in this study were considerably less frequent and less abundant in comparison with High Arctic glaciers. The highest density of tardigrades and rotifers constituted 53 and 118 ind./ml, respectively. Generalized linear models showed no relationship between the densities of fauna and biotic and abiotic factors. The densities of animals were significantly higher in granules than in mud. The difference in the densities of animals between granules and mud reflects a simple mechanistic removal of invertebrates from the sediment during its erosion by flushing which leads to mud formation. These processes may influence a random distribution of micro-fauna without clear ecological interactions with biotic and abiotic variables at the edge of the GrIS.     

Are the supportive structures of the tardigrade pharynx homologous throughout the entire group?

Based on the differences in position, structure and function of the cuticular supportive structures in the pharynx of representatives of two major groups of tardigrades, the Heterotardigrada and Eutardigrada, it is postulated that these structures are not homologous throughout the Tardigrada. Hithero, these structures have been termed placoids in both classes (fused placoids in Heterotardigrada versus macro- and microplacoids in Eutardigrada). It is proposed here that there are two different kinds of fused placoids within the Heterotardigrada and that only one of these is homologous to the macro- and microplacoids of the Eutardigrada. It is furthermore proposed that the plesiomorphic condition for the tardigrade pharynx is without reinforced cuticular supportive structures and not the presence of encrusted fused placoids as found in Heterotardigrada.     

Crystal structure of secretory abundant heat soluble protein 4 from one of the toughest “water bears” micro‐animals Ramazzottius Varieornatus

Though anhydrobiotic tardigrades (micro‐animals also known as water bears) possess many genes of secretory abundant heat soluble (SAHS) proteins unique to Tardigrada, their functions are unknown. A previous crystallographic study revealed that a SAHS protein (RvSAHS1) from one of the toughest tardigrades, Ramazzottius varieornatus, has a β‐barrel architecture similar to fatty acid binding proteins (FABPs) and two putative ligand binding sites (LBS1 and LBS2) where fatty acids can bind. However, some SAHS proteins such as RvSAHS4 have different sets of amino acid residues at LBS1 and LBS2, implying that they prefer other ligands and have different functions. Here RvSAHS4 was crystallized and analyzed under a condition similar to that for RvSAHS1. There was no electron density corresponding to a fatty acid at LBS1 of RvSAHS4, where a putative fatty acid was observed in RvSAHS1. Instead, LBS2 of RvSAHS4, which was composed of uncharged residues, captured a putative polyethylene glycol molecule. These results suggest that RvSAHS4 mainly uses LBS2 for the binding of uncharged molecules.     

Milnesium cfr. tardigradum (Milnesiidae, Apochela, Tardigrada): A Monitor of High Altitude Meiofauna on Sub-Antarctic Marion Island

The meiofaunal tardigrades Milnesium cfr. tardigradum, Echiniscus sp., and Macrobiotus sp. were extracted from high altitude moss and volcanic scoria samples on sub-Antarctic Marion Island. Gut contents of mounted Milnesium provided forensic evidence of a previously ignored diverse and abundant meiofauna including trophi of bdelloid rotifers, mouthparts and entire individuals of Diphascon sp. (Tardigrada).     

Location,location, location? No. Catalog number

Once you start to read this Editor’s Corner, you might wonder why I have devoted an entire article, albeit a short one, to this topic. Let me assure you there are reasons. First, I want to announce a new policy for the journal that will affect all research papers. Starting with all papers that are not currently in press, we will no longer be asking for geographical locations of research companies that follow the listing of a reagent. In Materials and Methods the authors typically refer to a reagent and then list the company and its location parenthetically. For example, “…p-nitrophenyl phosphate (Sigma-Aldrich, St. Louis, MO).” Instead, we will require catalog numbers. The reason is that it is now quite easy to find a company using the internet, and in fact you rarely need to know the location because it is rare that you would send a written order. On the other hand, knowing the name of the reagent is not always sufficient to narrow down the precise item. For example, if you search for “p-nitrophenyl phosphate” at the Sigma-Aldrich site, you get seven primary choices and it is not at all obvious which one to choose. When my lab uses p-nitrophenyl phosphate for the Pho8?60 assay, we use item N9389, which narrows it down to a precise reagent. Thus, we will start requiring papers to write “…p-nitrophenyl phosphate (Sigma-Aldrich, N9389).

Second, I think this is actually a useful change, and one that many journals will start to institute once they see it being done here. The old style of listing the city and state is a relic that is no longer relevant. Furthermore, it is not even clear in the current global marketplace if this is particularly helpful. For example, if I am ordering an item from Roche Applied Science, why would anyone care where it is coming from? It is highly unlikely that a researcher in Germany or Japan is going to order from Roche Applied Science that happens to be based in Indianapolis, IN when there are much closer sites in Mannheim, Germany and Tokyo, Japan. So, do not be surprised when you start to see more and more journals adopting this approach, and remember that you saw it here first. Autophagy—the cutting edge.     

Phylogeography of North Atlantic intertidal tardigrades: refugia,cryptic speciation and the history of the Mid‐Atlantic Islands

Aim To analyse the phylogeographical history of intertidal tardigrades in the North Atlantic in order to improve our understanding of geographical differentiation in microscopic organisms, and to understand the potential importance of the Mid‐Atlantic Islands as stepping stones between the American and European coasts of the Atlantic Ocean. Location Twenty‐four localities from the Mid‐Atlantic Islands (Greenland, Iceland and the Faroe Islands) and both sides of the North Atlantic Ocean. Methods A mitochondrial marker (cytochrome c oxidase subunit I) was sequenced from individual tardigrades belonging to the genus Echiniscoides. The existence of cryptic species was detected using generalized mixed Yule coalescence analysis; lineage ages were estimated with relaxed clock methods; and the degree of geographical differentiation was analysed with samova analyses, haplotype networks and Mantel tests. Results Echiniscoides hoepneri, previously known only from Greenland, was recovered throughout the Mid‐Atlantic Islands. The Faroe Islands population was isolated from Greenland and Iceland, but overall genetic variation was low. The morphospecies Echiniscoides sigismundi had high genetic variation and consisted of at least two cryptic species. A northern and a southern species were both recovered on both sides of the Atlantic, but only the northern species was found on the Mid‐Atlantic Islands. The northern species showed signs of long‐term isolation between the Western and Eastern Atlantic, despite the potential of the Mid‐Atlantic islands to act as stepping‐stones. There was no sign of long‐term isolation in the southern species. The Mid‐Atlantic individuals of the northern species were of Eastern Atlantic origin, but Greenland and Iceland showed signs of long‐term isolation. The genetic pattern found in the southern species is not clearly geographical, and can probably be best explained by secondary contact between former isolated populations. Main conclusions North Atlantic intertidal tardigrades from the genus Echiniscoides showed strong geographical differentiation, and the Mid‐Atlantic Islands seemed unimportant as stepping stones across the Atlantic. The geographical variation of the northern species of E. sigismundi suggests post‐glacial recolonization from several refugia.     

Occurrence and diversity of fungal entomopathogens in soils of low and high Arctic Greenland

Knowledge of the occurrence, distribution and diversity of pathogens of insects and arachnids (entomopathogens) in the Arctic is very limited. Climate change is expected to affect Arctic terrestrial arthropod communities and therefore also host–pathogen interactions, given that entomopathogens are present. We conducted a survey of fungal entomopathogens in soil samples collected at four localities in Greenland; two at low Arctic sites (Ritenbenk and Disko Island) and two at sites in the high Arctic (Zackenberg and Danmarkshavn). Fungi were isolated from soil samples using larvae of the insect species Galleria mellonella (Lepidoptera) and Tenebrio molitor (Coleoptera) as baits providing evidence that the fungal isolates were indeed entomopathogenic. Five fungal species (Ascomycota; Hypocreales) were found: Isaria fumosorosea Wize, Isaria farinosa (Holmsk.) Fr., Beauveria bassiana (Bals.) Vuill., Beauveria pseudobassiana Rehner and Humber and Tolypocladium inflatum W. Gams (syn.?=?T. niveum). I. farinosa was found at all four localities, while I. fumosorosea was detected in single samples at each of three localities including both high Arctic sites. Only the locality on Disko Island revealed B. bassiana, whereas B. pseudobassiana was isolated at the three other sites. T. inflatum was only found on Disko Island and only isolated with T. molitor as a bait insect. The results document that fungal entomopathogens are widely distributed in the soil environment in Greenland. Entomopathogens should therefore be included in future studies of arthropod ecology in the Arctic.     

Tardigrades — Are They Really Miniaturized Dwarfs?

Tardigrades are animals of small body size which is often regarded to be a secondary phenomenon. This interpretation makes sense in the traditional concept that tardigrades are closely related to Onychophora, Euarthropoda and Annelida. A large body size in the ancestor of this common taxon (Articulata) is probable. Small size and the absence of organs such as a dorsal heart, segmental coelomic cavities and metanephridia must then be interpreted as derived in tardigrades. However, when Cycloneuralia are taken as an outgroup instead of Annelida (taxon Ecdysozoa), an interpretation of small body size as a primary feature is plausible. This also accounts for the absence of heart, coelom and nephridia.The choice of outgroup influences hypotheses about sister-group relationships within Panarthropoda, with either Onychophora (Articulata-concept) or Tardigrada (Ecdysozoa-concept) being basal.