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First published online February 12, 2007
Journal of Experimental Biology 210, 836-844 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02714

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Slow dehydration promotes desiccation and freeze tolerance in the Antarctic midge Belgica antarctica

Scott A. L. Hayward^1,2,*, Joseph P. Rinehart^1,3, Luke H. Sandro⁴, Richard E. Lee, Jr⁴ and David L. Denlinger¹

¹ Department of Entomology, Ohio State University, Columbus, OH 43210, USA
² School of Biological Sciences, Liverpool University, Liverpool L69 7ZB, UK
³ Red River Valley Station, USDA-ARS, Fargo, ND 58105, USA
⁴ Department of Zoology, Miami University, Oxford, OH 45056, USA

View larger version (24K): [in this window] [in a new window]   Fig. 1. (A) Change in water content (g) per gram of dry mass (DM). (B) Percentage survival of larvae maintained under 100, 98.2 and 75% relative humidity (RH) conditions for up to 12 days. (C) Comparison of survival at different water contents under desiccating conditions of 75 and 98.2% RH. Least-squares fit plotted using the following equation: y=cln x+b. (D) Change in osmotically active water content (OAW) during exposure to 98.2% RH. (E) Change in body fluid osmotic pressure (bar) and/or osmolality during exposure to 98.2% RH (1 bar=100 kPa). The horizontal line denotes the environmental water potential. 100% RH (closed triangles), 98.2% RH (open squares), 75% RH (closed circles). Values shown are means ± s.e.m. for three replicates of 10 individuals.

View larger version (8K): [in this window] [in a new window]   Fig. 2. Survival of desiccated larvae following rehydration by either submergence in water or exposure to 100% relative humidity (RH). Larvae were desiccated at 98.2% RH for different durations and then rehydrated for 1 day. *Significant difference (P<0.05) between treatments at a given time point. Values shown are means ± s.e.m. for three replicates of 10 individuals.

View larger version (24K): [in this window] [in a new window]   Fig. 3. Changes in (A) osmolality (mOsm) and (B) mass (represented as a percentage of the initial fresh mass) during desiccation at 98.2% relative humidity (RH) for 24 h, followed by 1 h and 24 h of rehydration in water. C and D show changes in osmolality and mass, respectively, after 5 days of desiccation at 98.2% RH, followed by 1 h and 24 h of rehydration in water. Initial conditions refer to osmolality and mass values prior to desiccation. *Significant difference (P<0.05) from initial conditions. Values shown are means ± s.e.m. for at least three replicates of 10 individuals.

View larger version (4K): [in this window] [in a new window]   Fig. 4. Effect of a 48-h desiccation pretreatment at 98.2% relative humidity (RH) (squares) on cold tolerance at –10°C. Control (triangles). Values shown are means ± s.e.m. for at least three replicates of 10 individuals.

View larger version (17K): [in this window] [in a new window]   Fig. 5. Expression of the small hsp, hsp70 and hsp90 transcripts in fourth instar Belgica antarctica larvae in response to desiccation. Lanes represent RNA samples from larvae desiccated for different durations at 0, 75 and 98.2% relative humidity (RH). 28s ribosomal RNA was used as a control to confirm equal sample loading. Each sample was run in triplicate.