Soluble carbohydrates (trehalose in particular) and cryoprotection in polar biota.

Data are presented here on low molecular weight carbohydrates contents (assessed from samples collected in situ) of selected, representative terrestrial species from the maritime Antarctic. Significant seasonal variation for most species were observed. Increased levels overwinter in arthropods contrasted with cryptogams where levels were higher in spring and summer samples. The occurrence and seasonal variation of trehalose in particular is demonstrated for invertebrate and lichen species. The data are discussed in relation to published results from experimental manipulation of growth temperatures on Antarctic fungi and an Arctic springtail providing further evidence for the protective role of trehalose. The widespread presence of trehalose in polar biota is documented and discussed regarding acclimatisation to both low temperature and partial dehydration.

Partial desiccation induced by sub-zero temperatures as a component of the survival strategy of the Arctic collembolan Onychiurus arcticus (Tullberg).

The mechanism by which the freeze susceptible Arctic collembolan Onychiurus arcticus survives winter temperatures of -25 degrees C in the field is not fully understood but exposure to sub-zero temperatures (e.g. -2.5 degrees C) is known to induce dehydration and lower the supercooling point (SCP). In this study, changes in the water status and certain biochemical parameters (measured in individual Collembola) during a 3-week exposure to decreasing temperatures from 0 to -5.5 degrees C were studied. Osmotically active and inactive body water contents were measured by differential scanning calorimetry (DSC), water soluble carbohydrates by high performances liquid chromatography (HPLC) and glycogen by enzymatic assays. The activity of trehalase and trehalose 6-phosphate synthase were also measured. During the experiment, total water content decreased from 70 to 40% of fresh weight, mostly by the loss of osmotically active water with only a small reduction in the osmotically inactive component. The SCP decreased from -7 to -17 degrees C. Analysis of the results shows that if O. arcticus is exposed to -7 degrees C in the presence of ice, all osmotically active water would be lost due to the vapour pressure gradient between the animals supercooled body fluids and the ice. Under these conditions the estimated SCP would reach a minimum of c. -27 degrees C, but the Collembola may never freeze as all the osmotically active water has been lost, the animal becoming almost anhydrobiotic. Trehalose concentration increased from 0.9 to 94.7&mgr;g mg(-1)fw while glycogen reserves declined from 160 to 7.7 nmol glucose equivalents mg(-1) protein. Trehalase activity declined as the temperature was reduced, while trehalose 6-phosphate activity peaked at 0 degrees C. By adopting a strategy of near anhydrobiosis induced by sub-zero temperatures, O. arcticus, which was previously thought to be poorly adapted to survive severe winter temperatures, is able to colonise high Arctic habitats.