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Article
Published: 2018-09-10

Revision of Testechiniscus Kristensen, 1987 (Heterotardigrada: Echiniscidae) refutes the polar-temperate distribution of the genus

Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387 Kraków, Poland
Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387 Kraków, Poland
Institute of Environmental Sciences, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
Section of Biosystematics, Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387 Kraków, Poland
Tardigrada Afrotropic Antarctic Arctic glacial refugia Holarctic T. laterculus T. macronyx T. meridionalis T. spitsbergensis ventral plates

Abstract

The family Echiniscidae comprises limno-terrestrial heterotardigrades with a strongly sclerotised dorsum, typically covered with plates. Among other members of the Echiniscus evolutionary line, the genus Testechiniscus Kristensen, 1987 stands out with well-developed ventral armature and polygonal sculpturing of the dorsal plates. It has alleged bipolar distribution (with satellite alpine records in the Holarctic). Thanks to fresh material from terra typica (Svalbard), we integratively redescribe (i.e. using light and electron microscopy imaging, morphometry, and molecular methods) the nominal species for the genus, Testechiniscus spitsbergensis (Scourfield, 1897). A comparison of the neotype series with a number of Holarctic records revealed morphological variability suggesting that the species may encompass several taxa, which, most likely, will be possible to delineate primarily with molecular tools. Moreover, based on material from Simien Mountains (Northern Ethiopia), we describe a new sibling subspecies, Testechiniscus spitsbergensis tropicalis ssp. nov. Extensive morphometric datasets are provided for the genus members for the first time. A new generic definition is proposed, embracing the two subspecies of T. spitsbergensis and T. laterculus (Schuster et al., 1980), but excluding two circum-Antarctic species, T. macronyx (Richters, 1907) and T. meridionalis (Murray, 1906). The later species are likely to be erected in the future as separate genera, and their autapomorphies are described here. In the light of our findings, the genus          Testechiniscus should be recognised as a native element of the Northern Hemisphere, with mainly circum-Arctic distribution and additional, insular alpine records from the Nearctic, Palearctic and Eastern Afrotropic.

 

References

  1. Bartoš, E. (1935) Neue Echiniscus-Arten der nördlichen Slowakei. Zoologischer Anzeiger, 111, 139–143.

    Bartoš, E. (1936) Neue Tardigraden-Arten aus dem unterkarpatischen Russland. Zoologischer Anzeiger, 114 (1–2), 45–48.

    Biserov, V.I. (1996) Tardigrades of the Taimyr peninsula with descriptions of two new species. Zoological Journal of the Linnean Society, 116, 215–237.
    https://doi.org/10.1006/zjls.1996.0018

    Boeckner, M., Collins, M., Finney-Crawley, J. & Bateman, L. (2006) The bryofauna of remote coastal Labrador: including a review of current Canadian records. Zootaxa, 1105, 1–16.

    Bryce, D. (1922) On some Rotifera from Spitsbergen. The Oxford University Expedition to Spitsbergen, 1921. Journal of The Quekett Microscopical Club, Series 2, 14, 305–322.

    Carpenter, J.M. & Wheeler, W.C. (1999) Towards simultaneous analysis of morphological and molecular data in Hymenoptera. Zoologica Scripta, 28, 251–260.
    https://doi.org/10.1046/j.1463-6409.1999.00009.x

    Casquet, J., Thebaud, C. & Gillespie, R.G. (2012) Chelex without boiling, a rapid and easy technique to obtain stable amplifiable DNA from small amounts of ethanol-stored spiders. Molecular Ecology Resources, 12, 136–141.
    https://doi.org/10.1111/j.1755-0998.2011.03073.x

    Cuénot, L. (1926) Description d’un Tardigrade nouveau de la faune française. Comptes Rendus, 182, 744–745.

    Cuénot, L. (1932) Tardigrades. In: Lechevalier, P. (Ed.), Faune de France, 24, pp. 1–96.

    Dapporto, L. (2010) Speciation in Mediterranean refugia and post-glacial expansion of Zerynthia polyxena (Lepidoptera, Papilionidae). Journal of Zoological Systematics and Evolutionary Research, 48 (3), pp. 229–237.
    https://doi.org/10.1111/j.1439-0469.2009.00550.x

    Dastych, H. (1973) Systematic studies on Tardigrada. II. Echiniscus clavisetosus Mihelčič 1958, a synonym of Echiniscus spitzbergensis Scourfield 1897. Bulletin de la Société des Amis des Sciences et des Lettres de Poznań, Serie D, 14, 89–99.

    Dastych, H. (1984) The Tardigrada from Antarctica with descriptions of several new species. Acta Zoologica Cracoviensia, 27 (19), 377–436.

    Dastych, H. (1985) West Spitsbergen Tardigrada. Acta Zoologica Cracoviensia, 28, 169–214.

    Degma, P., Bertolani, R. & Guidetti, R. (2009–2018) Actual checklist of Tardigrada species. Version 34th Edition. 30 June 2018, pp. 48. Available from: www.tardigrada.modena.unimo.it/miscellanea/Actual%20checklist%20of%20Tardigrada.pdf (accessed 3 July 2018)

    Degma, P. & Schill, R.O. (2015) Echiniscus pardalis n. sp., a new species of Tardigrada (Heterotardigrada, Echiniscidae, arctomys group) from the Parco Naturale delle Alpi Marittime (NW Italy). Zoosystema, 37 (1), 239–249.
    https://doi.org/10.5252/z2015n1a12

    Doyère, M.L. (1840) Mémorie sur les Tardigrades. Annales des Sciences Naturelles. Zoologie, 14, 269–362.

    du Bois-Reymond Marcus, E. (1944) Sobre tardígrados brasileiros. Comunicaciones Zoologicas del Museo de Historia Natural de Montevideo, 1 (13), 1–19.

    Fontoura, P. & Morais, P. (2011) Assessment of traditional and geometric morphometrics for discriminating cryptic species of the Pseudechiniscus suillus complex (Tardigrada, Echiniscidae). Journal of Zoological Systematics and Evolutionary Research, 49 (Supplement 1), 26–33.
    https://doi.org/10.1111/j.1439-0469.2010.00594.x

    Gąsiorek, P. (2018) New Bryodelphax species (Heterotardigrada: Echiniscidae) from Western Borneo (Sarawak), with new molecular data for the genus. Raffles Bulletin of Zoology, 66, 371–381.

    Gąsiorek, P., Stec, D., Morek, W. & Michalczyk, Ł. (2017a) An integrative redescription of Echiniscus testudo (Doyère, 1840), the nominal taxon for the class Heterotardigrada (Ecdysozoa: Panarthropoda: Tardigrada). Zoologischer Anzeiger, 270, 107–122.

    https://doi.org/10.1016/j.jcz.2017.09.006

    Gąsiorek, P., Stec, D., Morek, W., Marnissi, J. & Michalczyk, Ł. (2017b) The tardigrade fauna of Tunisia, with an integrative description of Bryodelphax maculatus sp. nov. (Heterotardigrada: Echiniscidae). African Zoology, 52 (2), 1–13.

    https://doi.org/10.1080/15627020.2017.1297688

    Grigarick, A.A., Schuster, R.O. & Toftner, E.C. (1975) Morphogenesis of two species of Echiniscus. In: International Symposium on Tardigrades, 1974. Memorie dell'Istituto Italiano di Idrobiologia, 32 (Supplement), 133–151.

    Guidetti, R., Schill, R.O., Bertolani, R., Dandekar, T. & Wolf, M. (2009) New molecular data for tardigrade phylogeny, with the erection of Paramacrobiotus gen. nov. Journal of Zoological Systematics and Evolutionary Research, 47 (4), 315–321.
    https://doi.org/10.1111/j.1439-0469.2009.00526.x

    Guil, N. & Giribet, G. (2012) A comprehensive molecular phylogeny of tardigrades - adding genes and taxa to a poorly resolved phylum-level phylogeny. Cladistics, 28, 21–49.
    https://doi.org/10.1111/j.1096-0031.2011.00364.x

    Hall, T.A. (1999) BioEdit: a user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. Nucleic Acids Symposium Series, 41, 95–98.

    Heide-Jørgensen, H.S. & Kristensen, R.M. (1999) Puilassoq, the warmest homothermal spring of Disko Island. Berichte zur Polarforschung, 330, 32–43.

    Heinis, F. (1917) Tardigraden aus der Umgebung von Triest. Zoologischer Anzeiger, 49, 94–96.

    Homburg, K., Drees, C., Gossner, M.M., Rakosy, L., Vrezec, A. & Assmann, T. (2013) Multiple glacial refugia of the low-dispersal ground beetle Carabus irregularis: molecular data support predictions of species distribution models. PLOS ONE, 8 (4), e61185.
    https://doi.org/10.1371/journal.pone.0061185

    Iharos, G. (1961) Grundlage der Tardigradenfauna Bulgariens. Acta Zoologica Academiae Scientiarum Hungaricae, 7 (1–2), 111–118.

    Jørgensen, A. (2000) Cladistic analyses of the Echiniscidae Thulin, 1928 (Tardigrada: Heterotardigrada: Echiniscoidea). Steenstrupia, 25, 11–23.

    Jørgensen, A. & Kristensen, R.M. (2004) Molecular phylogeny of Tardigrada—investigation of the monophyly of Heterotardigrada. Molecular Phylogenetics and Evolution, 32, 666–670.
    https://doi.org/10.1016/j.ympev.2004.04.017

    Jørgensen, A., Møbjerg, N. & Kristensen, R.M. (2011) Phylogeny and evolution of the Echiniscidae (Echiniscoidea, Tardigrada)—an investigation of the congruence between molecules and morphology. Journal of Zoological Systematics and Evolutionary Research, 49 (1), 6–16.

    https://doi.org/10.1111/j.1439-0469.2010.00592.x

    Kaczmarek, Ł., Zawierucha, K., Smykla, J. & Michalczyk, Ł. (2012) Tardigrada of the Revdalen (Spitsbergen) with the descriptions of two new species: Bryodelphax parvuspolaris (Heterotardigrada) and Isohypsibius coulsoni (Eutardigrada). Polar Biology, 35, 1013–1026.
    https://doi.org/10.1007/s00300-011-1149-0

    Kathman, R.D. (1989) Studies on the Tardigrada of Vancouver Island, British Columbia. Unpublished Ph.D. Dissertation, University of Victoria, Victoria, B.C., 297 pp.

    Kathman, R.D. & Cross, S.F. (1991) Ecological distribution of moss-dwelling tardigrades on Vancouver Island, British Columbia, Canada. Canadian Journal of Zoology, 69, 122–129.
    https://doi.org/10.1139/z91-018

    Kathman, R.D. & Dastych, H. (1990) Some Echiniscidae (Tardigrada: Heterotardigrada) from Vancouver Island, British Columbia, Canada. Canadian Journal of Zoology, 68, 699–706.
    https://doi.org/10.1139/z90-102

    Katoh, K., Misawa, K., Kuma, K. & Miyata, T. (2002)—MAFFT: a novel method for rapid multiple sequence alignment based on fast Fourier transform. Nucleic Acids Research, 30 (14), 3059–3066.
    https://doi.org/10.1093/nar/gkf436

    Katoh, K. & Toh, H. (2008) Recent developments in the MAFFT multiple sequence alignment program. Brief Bioinformatics, 9 (4), 286–298.
    https://doi.org/10.1093/bib/bbn013

    Kristensen, R.M. (1987) Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. In: Bertolani, R. (Ed.), Biology of Tardigrada. Selected Symposia and Monographs. U.Z.I. Mucci, Modena, pp. 261–335.

    Kumar, S., Stecher, G. & Tamura, K. (2016) MEGA7: Molecular Evolutionary Genetics Analysis version 7.0 for bigger datasets. Molecular Biology and Evolution, 33 (7), 1870–1874.
    https://doi.org/10.1093/molbev/msw054

    Linnaeus, C. (1758) Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Vol. 1. 10th Edition. Laurentius Salvius, Stockholm, 824 pp.

    Marcus, E. (1927) Zur Anatomie und Ökologie mariner Tardigraden. Zoologische Jahrbücher abteilung für Systematik Ökologie und Geographie der Tiere, 53, 487–558.

    Marcus, E. (1936) Tardigrada. Das Tierreich, 66, 1–340.

    Maucci, W. (1996) Tardigrada of the Arctic tundra with descriptions of two new species. Zoological Journal of the Linnean Society, 116, 185–204.
    https://doi.org/10.1111/j.1096-3642.1996.tb02343.x

    McInnes, S.J. (1994a) Rediscovery of the species Echiniscus macronyx Richters, 1907 on South Georgia, South Atlantic, its new systematic position and redescription within the genus Testechiniscus. Bollettino di Zoologia, 61, 83–87.
    https://doi.org/10.1080/11250009409355863

    McInnes, S.J. (1994b) Zoogeographic distribution of terrestrial/freshwater tardigrades from current literature. Journal of Natural History, 28, 257–352.
    https://doi.org/10.1080/00222939400770131

    Meyer, H.A. & Hinton, J.G. (2007) Limno-terrestrial Tardigrada of the Nearctic Realm. Journal of Limnology, 66 (Supplement 1), 97–103.
    https://doi.org/10.4081/jlimnol.2007.s1.97

    Michalczyk, Ł. & Kaczmarek, Ł. (2013) The Tardigrada Register: a comprehensive online data repository for tardigrade taxonomy. Journal of Limnology, 72 (Supplement 1), 175–181.
    https://doi.org/10.4081/jlimnol.2013.s1.e22

    Mihelčič, F. (1951) Beiträg zur Systematik de Tardigraden. Archivio Zoologico Italiano, 36, 57–103.

    Mihelčič, F. (1958) Eine neue Tardigradenart feuchter Standorte. Zoologischer Anzeiger, 160 (5–6), 105–108.

    Mihelčič, F. (1967) Ein Beitrag zur Kenntnis der Tardigraden Argentiniens. Verhandlungen der Zoologisch-Botanischen Gesellschaft in Wien, 107, 43–56.

    Mironov, S.V., Dabert, J. & Dabert, M. (2012) A new feather mite species of the genus Proctophyllodes Robin, 1877 (Astigmata: Proctophyllodidae) from the Long-tailed Tit Aegithalos caudatus (Passeriformes: Aegithalidae): morphological description with DNA barcode data. Zootaxa, 3253, 54–61.

    Morek, W., Stec, D., Gąsiorek, P., Schill, R.O., Kaczmarek, Ł. & Michalczyk, Ł. (2016) An experimental test of tardigrade preparation methods for light microscopy. Zoological Journal of the Linnean Society, 178, 785–793.
    https://doi.org/10.1111/zoj.12457

    Murray, J. (1905) The Tardigrada of the Scottish Lochs. Transactions of the Royal Society of Edinburgh, 41, 677–698.
    https://doi.org/10.1017/S0080456800035547

    Murray, J. (1906) Scottish National Antarctic Expedition: Tardigrada of the South Orkneys. Transactions of the Royal Society of Edinburgh, 45 (12), 323–334.

    https://doi.org/10.1017/S0080456800022754

    Murray, J. (1907a) Arctic Tardigrada, collected by Wm. S. Bruce. Transactions of the Royal Society of Edinburgh, 45, 669–681.

    https://doi.org/10.1017/S0080456800011789

    Murray, J. (1907b) Scottish Tardigrada collected by the Lake Survey. Transactions of the Royal Society of Edinburgh, 45, 641–668.
    https://doi.org/10.1017/S0080456800011777

    Murray, J. (1910) Tardigrada. British Antarctic Expedition 1907–1909. Reports on the Scientific Investigations, 1, Biology (Part V), 83–187.

    Murray, J. (1911) Scottish Tardigrada. A Review of Our Present Knowledge. Annals of Scottish Natural History, 77, 88–95.

    Nelson, D.R. (2002) Current status of the Tardigrada: evolution and ecology. Integrative and Comparative Biology, 42, 652–659.
    https://doi.org/10.1093/icb/42.3.652

    Nelson, D.R. & Marley, N.J. (2000) The biology and ecology of lotic Tardigrada. Freshwater Biology, 44, 93–108.
    https://doi.org/10.1046/j.1365-2427.2000.00586.x

    Péterfi, F. (1956) Contributioni la Cunoaşterea Tardigradelor din R. P. R. Studii si Cercetari de Biologie, 7, 149–155.

    Peters, T. & Dumjahn, P. (1999) Ecological aspects of tardigrade distribution on Disko Island, West Greenland. Berichte zur Polarforschung, 330, 64–75.

    Petersen, B. (1951) The Tardigrade Fauna of Greenland. Meddelelser om Grønland, 150 (5), 1–94.

    Prendini, L., Weygoldt, P. & Wheeler, W.C. (2005) Systematics of the Damon variegatus group of African whip spiders (Chelicerata: Amblypygi): Evidence from behaviour, morphology and DNA. Organisms Diversity & Evolution, 5 (3), 203–236.
    https://doi.org/10.1016/j.ode.2004.12.004

    Ramazzotti, G. (1943) Nuova varieta del tardigrado Pseudechiniscus cornutus. Rivista di Scienze Naturali ′Natura′, 34, 89–90.

    Ramazzotti, G. (1958) Echiniscus merokensis con spine sulla piastra scapolare e variabilita di questa specie, anche nei confronti di E. quadrispinosus f. cribrosa (Tardigrada). Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale in Milano, 97 (1), 58–64.

    Ramazzotti, G. (1964) Tardigradi del Chile, III, con descrizione delle nuove specie Oreella minor e Pseudechiniscus lateromamillatus. Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano, 103, 347–355.

    Ramazzotti, G. & Maucci, W. (1983) Il Phylum Tardigrada. III edizione riveduta e aggiornata. Memorie dell' Istituto Italiano di Idrobiologia, 41, 1–1012.

    Richters, F. (1903) Nordische Tardigraden. Zoologischer Anzeiger, 27, 168–172.

    Richters, F. (1904) Arktische Tardigraden. Fauna Arctica, 3, 494–508.

    Richters, F. (1907) Antarktische Tardigraden. Zoologischer Anzeiger, 31, 915–916.

    Richters, F. (1908) Beitrag zur Kenntnis der Moosfauna Australiens und der Inseln des Pazifischen Ozeans. Zoologische Jahrbücher. Abteilung für Systematik, Ökologie und Geographie der Tiere, 26, 196–213.

    Richters, F. (1911a) Faune des mousses. Tardigrades. Duc d'Orleans. Campagne arctique de 1907. Imprimerie Scientifique, Bruxelles, 20 pp.

    Richters, F. (1911b) Moosfauna. Tardigrada. In: Koenig, A. (Ed.), Avifauna Spitzbergensis, Bonn, 1911, pp. 283–296.

    Richters, F. (1926) Tardigrada. In: Kükenthal, W. & Krumbach, T. (Eds.), Handbuch der Zoologie. Vol. 3. Walter de Gruyter & Co., Berlin and Leipzig, pp. 58–61.

    Sands, C.J., McInnes, S.J., Marley, N.J., Goodall-Copestake, W., Convey, P. & Linse, K. (2008) Phylum Tardigrada: an "individual" approach. Cladistics, 24, 1–18.
    https://doi.org/10.1111/j.1096-0031.2008.00219.x

    Schaudinn, F. (1901) Die Tardigraden. Fauna Arctica, 2, 186–196.

    Schultze, C.A.S. (1840) Echiniscus Bellermanni, Animal Crustaceum, Macrobioto Hufelandii affine. Apud G. Reimer, Berlin, 8 pp.

    Schuster, R.O. & Grigarick, A.A. (1965) Tardigrada from Western North America With Emphasis on the Fauna of California. University of California Publications in Zoology, 76, 1–67.

    Schuster, R.O., Grigarick, A.A. & Toftner, E.C. (1980) A New Species of Echiniscus from California (Tardigrada: Echiniscidae). Pan-Pacific Entomologist, 56 (4), 265–267.

    Scourfield, D.J. (1897) Contributions to the non-Marine Fauna of Spitsbergen. Part I. Preliminary Notes, and Reports on the Rhizopoda, Tardigrada etc. Proceedings of the Zoological Society of London, 65 (3), 784–792.
    https://doi.org/10.1111/j.1096-3642.1897.tb03120.x

    Stec, D. & Kristensen, R.M. (2017) An integrative description of Mesobiotus ethiopicus sp. nov. (Tardigrada: Eutardigrada: Parachela: Macrobiotidae: harmsworthi group) from the Northern Afrotropic region. Turkish Journal of Zoology, 41, 800–811.
    https://doi.org/10.3906/zoo-1701-47

    Stec, D., Smolak, R., Kaczmarek, Ł. & Michalczyk, Ł. (2015) An integrative description of Macrobiotus paulinae sp. nov. (Tardigrada: Eutardigrada: Macrobiotidae: hufelandi group) from Kenya. Zootaxa, 4052 (5), 501–526.
    https://doi.org/10.11646/zootaxa.4052.5.1

    Stec, D., Gąsiorek, P., Morek, W., Kosztyła, P., Zawierucha, K., Michno, K., Kaczmarek, Ł., Prokop, Z.M. & Michalczyk, Ł. (2016) Estimating optimal sample size for tardigrade morphometry. Zoological Journal of the Linnean Society, 178, 776–784.
    https://doi.org/10.1111/zoj.12404

    Stec, D., Zawierucha, K. & Michalczyk, Ł. (2017) An integrative description of Ramazzottius subanomalus (Biserov, 1985) (Tardigrada) from Poland. Zootaxa, 4300 (3), 403–420.
    https://doi.org/10.11646/zootaxa.4300.3.4

    Stewart, J.R., Lister, A.M., Barnes, I. & Dalén, L. (2010) Refugia revisited: individualistic responses of species in space and time. Proceedings of the Royal Society B: Biological Sciences, 277, 661–671.
    https://doi.org/10.1098/rspb.2009.1272

    Suatoni, E., Vicario, S., Rice, S., Snell, T. & Caccone, A. (2006) An analysis of species boundaries and biogeographic patterns in a cryptic species complex: The rotifer—Brachionus plicatilis. Molecular Phylogenetics and Evolution, 41 (1), 86–98.
    https://doi.org/10.1016/j.ympev.2006.04.025

    Thulin, G. (1911) Beträge zur Kenntnis der Tardigradenfauna Schwedens. Arkiv för Zoologi, 7, 1–60.
    https://doi.org/10.5962/bhl.part.1270

    Thulin, G. (1928) Über die Phylogenie und das System der Tardigraden. Hereditas, 11, 207–266.
    https://doi.org/10.1111/j.1601-5223.1928.tb02488.x

    Van Rompu, E.A. & De Smet, W.H. (1991) Contribution to the freshwater Tardigrada from Barentsøya, Svalbard (78°30′N). Fauna Norvegica, Series A, 12, 29–39.

    Vicente, F., Fontoura, P., Cesari, M., Rebecchi, L., Guidetti, R., Serrano, A. & Bertolani, R. (2013) Integrative taxonomy allows the identification of synonymous species and the erection of a new genus of Echiniscidae (Tardigrada, Heterotardigrada). Zootaxa, 3613 (6), 557–572.
    https://doi.org/10.11646/zootaxa.3613.6.3

    Wełnicz, W., Grohme, M.A., Kaczmarek, Ł., Schill, R.O. & Frohme, M. (2011) ITS-2 and 18S rRNA data from Macrobiotus polonicus and Milnesium tardigradum (Eutardigrada, Tardigrada). Journal of Zoological Systematics and Evolutionary Research, 49 (Supplement 1), 34–39.
    https://doi.org/10.1111/j.1439-0469.2010.00595.x

    Węglarska, B. (1965) Die Tardigraden (Tardigrada) Spitzbergens. Acta Zoologica Cracoviensia, 11, 43–51.

    White, T.J., Bruns, T., Lee, S. & Taylor, J. (1990) PCR protocols: a guide to methods and application. Academic Press, San Diego, California, 482 pp. [pp. 315–322]

    Zawierucha, K., Coulson, S.J., Michalczyk, Ł. & Kaczmarek, Ł. (2013) Current knowledge of the Tardigrada of Svalbard with the first records of water bears from Nordaustlandet (High Arctic). Polar Research, 32, 20886.
    https://doi.org/10.3402/polar.v32i0.20886

    Zawierucha, K., Podkowa, P., Marciniak, M., Gąsiorek, P., Zmudczyńska-Skarbek, K., Janko, K. & Włodarska-Kowalczuk, M. (in press) Temperature (latitude) and nutrient (seabird guano) effects on limno-terrestrial Tardigrada (Testechiniscus spitsbergensis and Pilatobius recamieri) body size. Polar Research.
    https://doi.org/10.1080/17518369.2018.1492297

    Zawierucha, K. Smykla, J., Michalczyk, Ł., Gołdyn, B. & Kaczmarek, Ł. (2015) Distribution and diversity of Tardigrada along altitudinal gradients in the Hornsund, Spitsbergen (Arctic). Polar Research, 34, 24168.

    https://doi.org/10.3402/polar.v34.24168

    Zawierucha, K., Zmudczyńska-Skarbek, K., Kaczmarek, Ł. & Wojczulanis-Jakubas, K. (2016) The influence of a seabird colony on abundance and species composition of water bears (Tardigrada) in Hornsund (Spitsbergen, Arctic). Polar Biology, 39, 713–723.
    https://doi.org/10.1007/s00300-015-1827-4

    Zeller, C. (2010) Untersuchung der Phylogenie von Tardigraden anhand der Genabschnitte 18S rDNA und Cytochrom c Oxidase Untereinheit 1 (COX I). Unpublished MSc Thesis, Technische Hochschule Wildau, Wildau, 105 pp.

    Zwolicki, A., Zmudczyńska-Skarbek, K., Iliszko, L. & Stempniewicz, L. (2013) Guano deposition and nutrient enrichment in the vicinity of planktivorous and piscivorous seabird colonies in Spitsbergen. Polar Biology, 36, 363–372.
    https://doi.org/10.1007/s00300-012-1265-5