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16 ARCTIC INSECT NEWS No. 9, 1998 will be done through a hole drilled in the sea ice. These reg u lar samplings will be co-ordinated with the CTD-measurements. Slightly col oured parts of the ice cores will be melted, and the wa - ter (hopefully) containing ice algae conserved. Ice algae/phytoplankton have been reg u larly sampled in the North Water polynya in both 1997 and 1998. The planned field work will in - crease the value of these already existing data, as it will be possible to say something about the inter-annual vari a tion in the spe cies as sem - blages. Furthermore, the sampling season from previous years will be ex tended. This is im por - tant in try ing to understand the dy nam ics be - tween ice al gae and phytoplankton. For in - stance, where do the species found in the spring bloom of algae in the water masses originate from? If they do originate from the ice, this would emphasise the importance of the ice al - gae in the biological pro duc tion in the area. Part of our planned field work will be bo - tanical, and carried out in co-operation with PhD. student Inger Greve Alsos at the Univer - sity of Tromsø, Norway. She is work ing with thermophilous arc tic plant spe cies, and her main field sites are on Svalbard. The most thermophilous plant species in this archipelago are ex tremely rare. Their few, small, and disjunct present-day pop u la tions may be frag - ments of more continuous pop u la tions orig i nat - ing from im mi grants to this arctic archipelago in a warmer climatic pe riod. Knowledge of the biology, his tory, and origin of the present north - ern outposts of such species is important be - cause northward expansion of southern spe cies is expected as a result of global warming. Greve Alsos stud ies the Svalbard pop u la tions and ref - erence pop u la tions from other areas (Scandina - via, Greenland, North ern Canada, Alaska and Siberia) of three model species (Betula nana s. lat., Vaccinium uliginosum s. lat., and Cam - panula rotundifolia s. lat.) for molecular ge - netic vari a tion (AFLPs, CAPs, RAPDs, isozymes), pop u la tion dynamics, morphology, and taxonomic re la tion ships. The data will be used to test if the pres ent Svalbard pop u la tions are frag mented relics or founded after re cent dispersal, and to ana lyse the relationships be - tween these pop u la tions and pop u la tions from possible source ar eas to es ti mate divergence times and immigration routes. The project is a co-operation between the Uni ver sities of Oslo and Tromsø, Nor way, and forms part of a larger research effort to strengthen international col - laboration on arc tic biodiversity and conserva - tion. We will be collecting plant material for Inger Greve Alsos along the west coast of Greenland and from Ellesmere Island (Herschel Bay and Alexandra Fiord) based on site de - scriptions given to us by her. More information on the expedition can be found on our website: http://www.sverdrup2000.org/. Questions can be addressed to the au thor at guldborg.sovik@bio.uio.no References Sverdrup, Otto. 1903. Nyt Land. Fire Aar i Arktiske Egne. Vol. I (“New Land. Four years in Arc tic Re gions”). In Nor we gian. H. Aschehoug & Co, Kristiania. Map taken from “Nyt Land” (New Land) by Otto Sverdrup, 1903. The expedition will overwinter approximately at ‘V.kvt.98-99’, just south of Hayes Sound, where Sverdrup overwintered with the vessel ‘Fram’ the first win ter.
ARCTIC INSECT NEWS No. 9, 1998 17 DEHYDRATION AND COLD HARDINESS IN THE COLLEMBOLAN ONYCHIURUS ARCTICUS Lauritz Sømme Department of Biology, University of Oslo, P.O. Box 1050, Blindern, N-0316 Oslo 3, Norway and Martin Holmstrup National Environmental Research Institute, Department of Terrestrial Ecology, P.O. Box 314, DK-8600, Silkeborg, Denmark Onychiurus arcticus rep re sents the first re - cord of a terrestrial ar thro pod that literally has to dry out to tol er ate freez ing tem per a tures (Holmstrup and Sømme 1998). Such a “pro tec - tive dehydration strategy” has previously been demonstrated in earthworm co coons from tem - per ate ar eas (Holmstrup and Zachariassen 1996) and in sev eral species of Enchytraeidae from Svalbard (Sømme and Birkemoe 1997). O. arcticus is widely distributed in northern areas of the Palaearctic re gion where it is abun - dant along sea shores (Fjellberg 1994). In bird cliffs at Spitsbergen, Svalbard, the species tol - erates –20 °C or lower temperatures dur ing the winter (Coulson et al. 1995). Unlike other polar and alpine Collembola, O. arcticus does not respond to the on set of win ter by in creased supercooling ca pac ity. During acclimation at 3, 0 or –3°C in the labora - tory, supercooling points remained at approxi - mately –7°C, and all specimens were killed by freezing. This makes it dif fi cult to understand how the collembolans can survive in their nat u - ral hab i tat. Due to the low water vapour pres sure above ice, unfrozen invertebrates are likely to lose wa - ter. When specimens of O. arcticus were placed in closed con tain ers over ice at –3°C, their wa - ter con tent fell from 3.0 to 1.5 g g -1 dry weight in two weeks. At the same time the melting point of their body fluids fell from –0.7 to –3°C. Similar pe ri ods at lower experimental tempera - tures resulted in even lower water contents, e.g. 0.25 g g -1 dry weight at -19.5°C. Following slow warming to above-zero tem per a tures, 80 to 90% sur vival was recorded in all groups. Fol low ing con sid er able wa ter loss in a group of spec i mens kept at –8°C, a mean supercooling point of –22°C was recorded. In individuals acclimated over ice at –12°C or lower, no supercooling points could be re - corded, probably because all freez able water had been lost. In con clu sion, this ex per i men tal study shows that O. arcticus will undergo dehydra - tion when exposed to subzero temperatures in its natural frozen hab i tat. Con se quently, the melting points and supercooling points are low - ered and in this way freez ing is avoided. It is not unlikely that this protective dehydration strat - egy may be found in other soil invertebrates in polar re gions. References Coulson, S., Hodkinson, I.D., Strathdee, A.T., Block, W., Webb, N.R., Bale, S.J. and Worland, M.R. 1995. Thermal environment of arctic soil organisms during winter. Arctic Alpine Res. 27:364-370. Fjellberg, A. 1994. The Collembola of the Norwegian Arctic islands. Nor. Polarinst. Meddr. 133:1-57. Holmstrup, M. and Zachariassen, K.E. 1996. Physiology of cold hardiness in earthworms. Comp. Biochem. Physiol. A. 115:91-101. Holmstrup, M. and Sømme, L. 1998. Dehydration and cold hardiness in the Arctic Collembolan Onychiurus arcticus Tullberg 1876. J. Comp. Physiol. B 168:197-203. Sømme, L. and Birkemoe, T. 1997. Cold tolerance and dehydration in Enchytraeidae from Svalbard. J. Comp. Physiol. B 167:264-269.
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