Water acquisition and partitioning in Drosophila melanogaster: effects of selection for desiccation-resistance
Donna G. Folk*,
Christine Han and
Timothy J. Bradley
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697-2525, USA

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Fig. 1. Comparison of wet and dry masses of desiccation-selected flies (D flies) and their controls (C flies) at four phases of development. Values are means of five populations from either the C or D selection treatments ± S.E.M. The asterisk denotes a significant difference between the C and D flies, which was observed only in wet mass at 4 days post-eclosion (P<0.001).
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Fig. 2. Comparison of percentage body water content of desiccation-selected flies (D flies) and their controls (C flies) at five phases of development. Values are means of five populations from either the C or D selection treatments ± S.E.M. The asterisk denotes a significant difference between the C and D flies in percentage body water, which was observed only at 4 days post-eclosion (P<0.001).
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Fig. 3. Total body water volume measured at 10 min, 1 h, 2 h and 4 h following eclosion. The slopes of the regressions were not significantly different from zero for either the C flies (P=0.36) or the D flies (P=0.98). Values are means ± S.E.M. of five populations from either the C or D selection treatments.
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Fig. 4. Only a weak relationship was observed between survival during desiccation and intracellular water volume (r2=0.34, P=0.054). Each filled circle represents the mean (± S.E.M.) from one of the five D populations, while each open circle represents the mean (± S.E.M.) from one of the five C populations (N=10 flies per population).
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Fig. 5. A strong relationship was observed between survival during desiccation and hemolymph volume (r2=0.85, P=0.0002). Each filled circle represents the mean value (± S.E.M.) from one of the five D populations, while each open circle represents the mean (± S.E.M.) value from one of the five C populations (N=10 flies per population). Hemolymph data were log-transformed prior to statistical analyses.
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Fig. 6. Comparison of carbohydrate level adjusted for total dry mass between C and D populations at 4 days post-eclosion. Values are means ± S.E.M. of five populations from either the C or D selection treatments. The asterisk denotes a significant difference between the C and D flies in carbohydrate content (P=0.02).
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Fig. 7. The relationship between mean survival during desiccation and mean carbohydrate content adjusted for total dry mass (r2=0.77, P=0.032). Each point is the mean value (± S.E.M.) from one of the five desiccation-selected populations (N=10).
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© The Company of Biologists Ltd 2001