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First published online March 9, 2004
Journal of Experimental Biology 207, 1287-1294 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00880

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Metabolism of the sub-Antarctic caterpillar Pringleophaga marioni during cooling, freezing and thawing

Brent J. Sinclair^*, C. Jaco Klok and Steven L. Chown

Spatial, Physiological and Conservation Ecology Group, Department of Zoology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa

View larger version (25K): [in a new window]   Fig. 1. Representative data plots of temperature (grey, upper lines) and CO2 production (black, lower lines) from Pringleophaga marioni caterpillars exposed to freezing treatments at (A) –5.8°C (in which all caterpillars survive), (B) –6°C (which results in caterpillars being left moribund and then dead) and (C) –18°C (after which no caterpillars show muscle tone or response to stimuli). Breakpoint (b) and temperature of crystallisation (Tc) are marked. Small cycles in the CO2 trace shown in B are a result of minor temperature fluctuations at the IRGA. Whenever the range of these fluctuations exceeded the mean, the data were discarded. The break in the middle graph represents a change in data files (we were restricted by the memory that the acquisition software was able to allot to data gathering), and the slight difference in trace afterwards (equivalent to a maximum of 2.1 µW) is a result of re-baselining mid-data-acquisition. The masses of the caterpillars used in the presented data were 0.2342 g (A), 0.1977 g (B) and 0.3826 g (C), accounting for the variation in the scale of the right-hand y-axes.

View larger version (27K): [in a new window]   Fig. 2. Mass-corrected metabolic rate of Pringleophaga marioni larvae at different stages of freezing and thawing. Treatments: grey bars, –5.8°C; stippled bars, –6°C; hatched bars, –18°C. Means ± S.E.M. are presented. Although mass-specific data are presented here, analyses were performed as a repeated-measures analysis of covariance, with mass as a covariate. Bars with the same letter are not significantly different from one another (Tukey's HSD, P<0.05).

View larger version (47K): [in a new window]   Fig. 3. Water lost by Pringleophaga marioni caterpillars after freezing, measured by (A) infra-red gas analyzer before freezing and after thawing during the same run (note that quantity of water lost is standardized to different time periods) and (B) by total mass lost during the run. Grey bars, –5.8°C; stippled bars, –6°C; hatched bars, –18°C. (A) IRGA data are medians ± minimum and maximum. Sample sizes: –5.8°C (N=4); –6°C (N=6); –18°C (N=4). (B) Mass loss data were analysed as an ANCOVA with starting body mass as a covariate, although mass-specific means ± S.E.M. are presented. Sample sizes: –5.8°C (N=9); –6°C (N=8); –18°C (N=5).