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First published online March 8, 2005
Journal of Experimental Biology 208, 869-879 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01455

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Deleterious effects of repeated cold exposure in a freeze-tolerant sub-Antarctic caterpillar

Brent J. Sinclair^* and Steven L. Chown

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

^* Author for correspondence at present address: Department of Biological Sciences, University of Nevada, Las Vegas, NV 89154-4004, USA (e-mail: celatoblatta{at}yahoo.co.uk)

Accepted 15 December 2004

Multiple freeze–thaw cycles are common in alpine, polar and temperate habitats. We investigated the effects of five consecutive cycles of approx. –5°C on the freeze-tolerant larvae of Pringleophaga marioni Viette (Lepidoptera: Tineidae) on sub-Antarctic Marion Island. The likelihood of freezing was positively correlated with body mass, and decreased from 70% of caterpillars that froze on initial exposure to 55% of caterpillars that froze on subsequent exposures; however, caterpillars retained their freeze tolerance and did not appear to switch to a freeze-avoiding strategy. Apart from an increase in gut water, there was no difference in body composition of caterpillars frozen 0 to 5 times, suggesting that the observed effects were not due to freezing, but rather to exposure to cold per se. Repeated cold exposure did not result in mortality, but led to decreased mass, largely accounted for by a decreased gut mass caused by cessation of feeding by caterpillars. Treatment caterpillars had fragile guts with increased lipid content, suggesting damage to the gut epithelium. These effects persisted for 5 days after the final exposure to cold, and after 30 days, treatment caterpillars had regained their pre-exposure mass, whereas their control counterparts had significantly gained mass. We show that repeated cold exposure does occur in the field, and suggest that this may be responsible for the long life cycle in P. marioni. Although mean temperatures are increasing on Marion Island, several climate change scenarios predict an increase in exposures to sub-zero temperatures, which would result in an increased generation time for P. marioni. Coupled with increased predation from introduced house mice on Marion Island, this could have severe consequences for the P. marioni population.

Key words: climate change, fitness consequence, freeze–thaw cycle, Lepidoptera, Pringleophaga marioni

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