Progress in research on water bears presented at the 15th International Symposium on Tardigrada (Kraków, 22nd–26th of August 2022)

The International Symposium on Tardigrada is the only cyclical global meeting of people interested in water bears. Tardigrades are microscopic invertebrates known to a wider public thanks to their remarkable abilities to withstand extreme environmental conditions (including outer space) and for their adorable looks (a rare trait among microscopic metazoans). Although there is no formal tardigradological society that organises periodical meetings, international tardigrade conferences have been held for nearly half a century. So far, there have been fifteen tardigrade Symposia, each organised by different volunteer tardigradologists. To date, these conferences have taken place in Italy (Pallanza in 1974, Modena in 1985 and 2015, and Catania in 2006), the USA (Johnson City, TN in 1980, College Park, MD in 1992, and Saint Pete Beach, FL in 2003), Poland (Kraków in 1977 and 2022), Germany (Düsseldorf in 1997 and Tübingen in 2009), Denmark (København in 2000 and 2018), the UK (Cambridge in 1994), and Portugal (Villa Nova de Gaia in 2012). The next, 16th Symposium, is planned to be held in Tsuruoka, Japan, 23rd–27th June 2025. Moreover, the 17th and the 18th Symposium have been tentatively planned in the USA (Chapel Hill, NC in 2028) and in Poland (Poznań in 2031), respectively. All these three cities will host the meeting for the first time, and the Symposium in Japan will be the first outside Europe and the USA. Symposia are typically held every three years and each congress is an extremely important event for the tardigrade research community, as it is a rare occasion for tardigradologists to meet in person. The 15th International Symposium on Tardigrada (Fig. 1, SM.01) was the second tardigrade conference held in Poland. The previous meeting in the country, the 2nd International Symposium on Tardigrada, took place in 1977 and it was hosted by the late Professor Barbara Węglarska (Michalczyk et al. 2024). The 15th Symposium was originally planned for 23rd–27th August 2021 (Møbjerg et al. 2020), but due to the COVID-19 pandemic, the congress was postponed. Despite travel difficulties related to the pandemic and a war next door in Ukraine, after 45 years, the Symposium came back to Kraków and to the Jagiellonian University (JU) in 2022. The Symposium took five days and was attended by a total of 119 participants from 18 countries (Poland, United States, Japan, Denmark, Italy, Germany, Ukraine, Czechia, Finland, United Kingdom, Argentina, China, Philippines, Sweden, France, South Korea, Austria, and Canada) representing 4 continents (Europe, North America, Asia and South America); Fig. 2 (more photos in SM.02). In addition to regular participants, invited speakers and accompanying persons, an accredited journalist also attended the meeting. We were especially glad to welcome the senior members of our community, Professor Diane Nelson and her husband Jack (who are the only people to have attended all tardigrade symposia to date), and Professor Reinhardt Møbjerg Kristensen. Students made up over 40% of Symposium participants, which is an encouraging outcome for the future development of the field. The 15th Symposium was held at the Auditorium Maximum (33 Krupnicza Street), a modern and spacious conference centre of the JU, one of the oldest functioning universities in the world. Apart from lectures and presentations, there was a Welcome Reception followed by an icebreaker social and visits to various historic sites in and around Kraków, and a Banquet concluding the Symposium. The 15th International Symposium on Tardigrada logo, which depicts an individual of Doryphoribius dawkinsi stylised as the statue of the Wawel Dragon (by Bronisław Chromy) at the foot of the Wawel Hill in Kraków. Font and the outer flame colours represent the colours of the Jagiellonian University coat of arms. Concept and design: Łukasz Michalczyk (Jagiellonian University), artwork: Kamil Janelt (University of Silesia) & Ł.M. Participants of the 15th International Symposium on Tardigrada on the 23rd of August 2022 in front of the Jagiellonian University Auditorium Maximum at Krupnicza 33 in Kraków. A – a traditional shot; B – a drone shot. Photos by Adam Koprowski. See SM.02 for more photos and for videos from the 15th Symposium. The Symposium was divided into four major themes: Section I (Monday–Tuesday, 16 talks) was devoted to tardigrade Biodiversity, Taxonomy, Biogeography, Phylogeny & Evolution, Section II (Tuesday, 5 talks) addressed Ecology, Life Histories & Behaviour, Section III (Wednesday, 6 talks) was dedicated to Morphology, Anatomy, Reproduction & Development, and Section IV (Thursday–Friday, 20 talks) comprised lectures on Physiology, Omics, Cryptobiosis & Astrobiology. Each session was accompanied by a special illustration (Fig. 3) displayed on screens in the Auditorium Maximum (Michalczyk & Janelt 2024a,b, Janelt & Michalczyk 2024a,b). These illustrations, which serve as section dividers in this Special Issue, were also printed as postcards and given to all Symposium participants. In parallel to talk sessions, there were also two poster sessions, one on Physiology, Morphology & Ecology (Monday–Tuesday, 31 posters) and the other on Biodiversity (Wednesday–Thursday, 34 posters). Thus, in total, there were 52 talks and 69 posters presented at the Symposium. Illustrations used to open the four themed sessions during the 15th International Symposium on Tardigrada: A – Biodiversity, Taxonomy, Biogeography, Phylogeny & Evolution; B – Ecology, Life Histories & Behaviour; C – Morphology, Anatomy, Reproduction & Development; D – Physiology, Omics, Cryptobiosis & Astrobiology. These illustrations are also used as section dividers in the present Proceedings (see Michalczyk & Janelt 2024a,b and Janelt & Michalczyk 2024a,b for more details). Each of the first four days was opened with a lecture by an Invited Speaker (Fig. 4A–D): on Monday, Dr. Gregory Edgecombe from the Natural History Museum in London, UK, presented “A timeline for ecdysozoan diversification”, on Tuesday, Professor Andreas Hejnol from the Friedrich Schiller University in Jena, Germany, talked about “Tardigrades in development and evolution”, on Wednesday, Dr. Frank Smith from the University of North Florida in Jacksonville, USA, presented “The tardigrade Hypsibius exemplaris as a model for body plan evolution”, and on Thursday, Professor Nadja Møbjerg from the University of Copenhagen, Denmark, shed light on “Unravelling the mechanisms underlying extreme stress tolerance in tardigrades”. Each talk session was co-chaired by two persons (in order of appearance): Paul Bartels & Oscar Lisi, Reinhardt Møbjerg Kristensen & Krzysztof Zawierucha, Sandra McInnes & Atsushi Suzuki, Diane Nelson & Sara Calhim, Roberto Guidetti & Izabela Poprawa, Kazuharu Arakawa & Aslak Jørgensen, Nadja Møbjerg & Ingemar Jönsson, Tiziana Altiero & Łukasz Kaczmarek, Frank Smith & Vladimir Gross. Poster sessions also had Chaperons (in order of appearance): Piotr Gąsiorek & Witold Morek, Alejandro López-López & Pritam Dey. A few colleagues who in the end were not able to come to Kraków, sent videos with their talks which were screened as parts of the sessions. Also, a short video with Yevgen Kiosya from the V.N. Karazin Kharkiv National University was shown during the Opening Ceremony, in which he thanked the community for the support he has received since the beginning of the Russian invasion of Ukraine. Some impressions from the 15th International Symposium on Tardigrada: A–D keynote speakers presenting their talks in the Auditorium Maximum (A – Greg Edgecombe, B – Andreas Hejnol; C – Frank Smith; D – Nadja Møbjerg); E – Young Scientist Award winners with their medals and diplomas at the Symposium Banquet in Stara Zajezdnia (from left: Ana Lyons – silver in physiology, Kamil Janelt – silver in zoology, Napat Emdee – gold in physiology, and Matteo Vecchi – gold in zoology); F – Student Volunteers in the Auditorium Maximum (top row – team Kraków, bottom row – team Katowice); G – a moment at the Opening Ceremony in the Auditorium Maximum (Łukasz Michalczyk welcoming participants and introducing keynote speakers); H – a moment from the Closing Ceremony in the Auditorium Maximum (Astushi Suzuki and Kazu Arakawa inviting tardigrade enthusiast to the 16th Symposium). Photos A–D and G–H by Adam Koprowski, E by Atsushi Suzuki, and F by Łukasz Michalczyk. There were 21 oral and 21 poster presentations that competed for the Young Scientist Awards (YSA). The YSA Committee (Łukasz Michalczyk – Chair, Diane Nelson, Nadja Møbjerg, Kazuharu Arakawa, Sara Calhim & Vladimir Gross), had a tough task of choosing the best talks and posters in the fields of zoology and physiology. This was the first Symposium at which in addition to financial prizes, medals were also awarded: gold for best talks and sliver for best posters (Fig. 4E). The gold medal in zoology was awarded to Dr Matteo Vecchi (Jyvaskyla University, Finland), for his talk “Evolution of sperm morphology in Macrobiotoidea”. The gold medal in physiology went to Napat Emdee, MSc (University of Copenhagen, Denmark), for his talk “Investigation of osmobiosis in the limno-terrestrial eutardigrade Ramazzottius varieornatus”. The silver medal in zoology was given to Kamil Janelt, MSc (University of Silesia, Poland), for his poster “Structural analysis of the cuticle and cuticular capsule in freshwater tardigrade Thulinius ruffoi”. Finally, the silver medal in physiology was awarded to Dr Ana Lyons (University of California San Francisco, USA), for her poster “Building a framework for tardigrade transgenics: identification and evaluation of candidate genetic promoters”. Furthermore, 12 young researchers were awarded Travel Grants to partially cover their travel, accommodation, and registration fees (costs were completely covered for the four Ukrainian student participants, who fled Kharkiv and settled at Polish Universities after the war broke out). In addition to talks and posters, there was also a spontaneous taxonomic roundtable on Thursday. The roundtable fits in the ongoing global debate on the future of biological taxonomy and systematics (e.g. see Pleijel et al. 2008, Padial et al. 2010, Haszprunar 2011, Johnson 2012, Carstens et al. 2013, Fišer et al. 2018, Vinarski 2020, Shin and Allmon 2023, Rheindt et al. 2023, and literature cited therein). The assembly was sparked by one of the Tuesday talks which argued that DNA sequences are not just another line of evidence that can but do not have to be used when delineating new species. The Tuesday talk reasoned that genetic data are a game-changer and should be considered by the community as essential in tardigrade taxonomy due to the mounting evidence for species crypsis on one hand, and cases of extreme instar-specific phenotypic variability on the other, which, in consequence may lead to under- and over-estimation of species diversity, respectively. Moreover, it was argued that tardigrade systematics should accelerate the transformation towards natural classification and artificial taxa should be suppressed if sound molecular phylogenetic analyses expose cases of anacladogenesis which result in the lack of reciprocal monophyly of the currently recognised taxa. There were two contrasting views expressed at the Thursday roundtable: some researchers supported the urgent need of switching from classical to integrative taxonomy, whereas other scholars argued that both classical and integrative taxonomy are valid and everyone should publish new taxa descriptions using the framework they prefer. The second group pointed out that marine tardigrades are rare and often preserved in formaldehyde, which limits the availability of specimens that can be used for DNA Some that integrative taxonomy can be as using all data at the which that DNA is not a for integrative also argued that a next may completely new and DNA may be Moreover, not everyone has and to DNA into their is that not all researchers who genetic data the genetic of Furthermore, are and are not with There are a few of species that were using molecular data and should not be Some that often species with morphology are DNA are not for all new can their was also argued that morphology more a of Finally, it was pointed out that species descriptions in cases when DNA data be will which is a in of the currently the In the of integrative taxonomy argued that marine tardigrades a different it is to for genetic analyses and there are a of that marine species and their with the of Moreover, given that of sequences from of taxa have been in for more a should at to to the integrative framework in this tardigrade it is that not everyone has the for to DNA there are a of the which are to DNA analyses with classical Moreover, it was that by to up with to the that taxonomy is a of to to that on In of research not be for if they do not present data with the Some researchers from countries it may be for to DNA (e.g. to to preserved in and which for the of especially that with and some will be In sequences in are and can be in and do not was argued that if data that DNA can which be with the of phenotypic data (e.g. species should DNA if future will be more Moreover, sequences it to for more was that should all to of the used DNA but it was that at the and are short and their sequences typically their was also that should species on genetic should be and that DNA sequences not with data have it was also that data also have Thus, should both of evidence to as as Furthermore, it was that a few genetic the of for analysis is the of the used DNA for some species morphology can be used to their phylogenetic there also are of and molecular especially in in phenotypic as of molecular with data that in these cases it is morphology that is Thus, due to do not to The of the integrative also argued that it in cases when DNA sequences are not at a it is to a species as a new species and but it as a new a new species genetic data in the in for if a is a of new of species. was also that DNA sequences with are for especially on for which data are of no Finally, it was that genetic data for more a of new and sequences with The of the roundtable was that need more to these and that will which classical is for tardigrade and of the To and and future meetings, an was presented by the to the tardigrade community (Fig. The Symposium was to be a of the of tardigrade the of the there is a in and to the are of the cities and years in which all previous Symposia were held of for future the there is a by the Jagiellonian University in Kraków, August The was to the and the of the 15th Symposium (Fig. was to the of the Tardigrada meeting at the end of the Closing Ceremony (Fig. with that the will to be on and used at future In addition to traditional as with a Symposium logo, participants were also given some more as in the of tardigrades and their (Fig. There were also at the icebreaker social on and during the on Barbara and four after some tardigrade and The Symposium and on the all tardigrade Symposia held to Photos by Łukasz Michalczyk & in the of Doryphoribius and the of were among the given to the 15th Symposium participants for for are in and by Łukasz The Symposium was organised by the and the in with the International and and with the of Student Łukasz Michalczyk (Jagiellonian University, Piotr Witold Morek, Alejandro and Pritam from the Izabela and Kamil Janelt from the University of Silesia, and Łukasz and Krzysztof from the Adam University, International Nadja Møbjerg (University of Copenhagen, Denmark), Vladimir (University of University, Yevgen Kiosya Karazin Kharkiv National University, Atsushi Suzuki University, Kazuharu Arakawa University, (University of University, and Roberto Guidetti (University of Modena and Barbara (Jagiellonian University, Poland), Reinhardt Møbjerg Kristensen (University of Copenhagen, Denmark), Diane Nelson University, USA), (University of and Roberto (University of Modena and Student Pritam and from the and from the Fig. This was the first when researchers from and in the Symposium Professor Barbara Węglarska was to the 2022 to see her and to meet new the and the 15th Symposium. To Barbara and her to tardigrade both the 15th Symposium and the Symposium Proceedings have been dedicated to her and (Michalczyk et al. 2024). the Symposium but these also our to Dr – 16th an Polish tardigrade who the second of his in Germany, and Dr Sandra – a tardigrade In these hosted by the of the present research one and a devoted to the late Professor Barbara one Symposium was in et al. The to the Symposium, are organised in four each with an illustration to the (Michalczyk & Janelt 2024a,b, Janelt & Michalczyk 2024a,b). Section I The by et al. the first of tardigrade with the of environmental DNA and the of in which limits the of the also that that with of may taxonomic in the The five taxonomy and systematics of tardigrade et al. a new of which cuticular which – to in the – that DNA analysis the two are not related to each other, the an of of of in The also that a new to the of the they from an species and the phylogenetic of the are used to for the of integrative taxonomy and natural classification in tardigrade Gąsiorek et al. to species in the are by with species recognised and the lack of DNA for of the currently known species. The a of from continents and they expose two (a and a species be of the of the and the species for the is to species in the et al. the phylogenetic of the a known only from that is to which the of the and the of the Moreover, that the of the order followed the the species and new in the new that species. et al. two new species in the Ramazzottius by cuticular and the with cuticle and the with and the of integrative data for species were DNA and DNA sequences in are not with are not This in this the of the two as new and the of the to be that more should be made to the known as this should to the the and for the candidate species as new taxa. Finally, et al. species of the of tardigrades by some as the and as the by other of their of and the – of The also three new species and new species different it was on phenotypic genetic and also using different DNA with phenotypic more the The that and phenotypic data are for species but they be to Section II of three et al. body of tardigrade species is related to by data on and body from species descriptions and with and data from the of the species. In after for and phylogenetic the body with the environmental The was for of the when each was The is the first analysis the in Guidetti et al. a in and to tardigrade in the and to it in to some as and more tardigrades and their from more and the classical taxonomy framework using phenotypic into species representing also that species with with and not with Moreover, the tardigrade was in and community and but not with The that the diversity, whereas the community of et al. if the by the COVID-19 tardigrade species in an Although species during the The of species to with and they that of over Section III two et al. and other the of three tardigrade species by with the and of the to a using and the that the of and other the to as and Bartels et al. a but in data from and the that a of various – not just the cuticle – are for the of colours and The it to a biological in these Section IV five Emdee et al. a analysis of Ramazzottius tardigrades a of by The that osmobiosis and to no only in et al. new data to the of in a for of the with in the the of the of tardigrade species. This is supported by to out as as a to the the of the on the tardigrade to be this data that are in line with from other et al. the of various to of which are present in and a to the of on The that all the and Tardigrada, were able to extremely of This has for research on their in development of biological with and on et al. the of Hypsibius exemplaris to an environmental of natural of the in of and is also et al. tardigrade known to to and in tardigrade and molecular but important Symposium Symposium of talks and posters, and of participants and their details). and by Łukasz Michalczyk. Photos and short videos from the 15th International Symposium on Tardigrada by Adam Koprowski, Łukasz Michalczyk and Reinhardt Kristensen. with and for Doryphoribius and and Łukasz no with all three as and The Symposium not have been the support of people and The of the Symposium was the Polish of and awarded to Ł.M. the the for conferences The Symposium was also supported by and We are also to the of the Jagiellonian University, Professor for the Symposium his We thanks to the for and and Section for especially and for their in up the Symposium and the registration as as for all their support during the of the Symposium and during the event We also to the for her in for We are to session and as as to student who the Symposium from welcoming our at the Kraków on to the in keynote speakers extremely and made was and our Adam Koprowski, took photos for the first in the of Symposia, some taken with a SM.02). We are also extremely to the of London, the of the and University for a for presented at the Symposium. Special thanks to and the previous and the of the as as to the who all made the of the 15th Symposium Proceedings Finally, all this not have been the participants. Thus, on of the to all for to Kraków and the 15th International Symposium on Tardigrada a for and which our community for and to see in Japan in The that they have no

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