Authors: T C Hawes D A Wharton
Publish Date: 2011/04/07
Volume: 167, Issue: 1, Pages: 39-48
Abstract
The adaptive fitness of a freezetolerant insect may be mediated by both endogenous and exogenous interactions The aim of the study presented here was to characterize the freeze tolerance of alpine Tiger moth caterpillars Metacrias huttoni and highlight two poorly explored indices of the potential attrition of fitness 1 downstream development and reproduction 2 parasitism Caterpillars survived temperatures as low as −16°C and demonstrated 90 72h survival after exposures to −10°C Twoweek acclimations at 5 10 and 20°C had no effect on body water content haemolymph osmolality or survival of equilibrium freezing but there was a significant elevation of the temperature of crystallization T c in those caterpillars acclimated to 5°C Cell viability of fat body tissue was resilient to freezing −10 to −16°C but midgut and tracheal cells showed significant degradation Pupation and eclosion were unaffected by freezing at −5 or −10°C Likewise there were no significant differences in egg production or the proportion of eggs that hatched between control and frozen insects By contrast the ability of tachinid larvae to survive freezing within their hosts means that parasitism plays an important role in regulating population size Mean parasitism of caterpillars by tachinids was 333 ± 72 Pupation and imago emergence of tachinids after host ‘endonucleation’ was 75 Eclosed adult tachinids showed a nonsignificant increase in the incidence of wing abnormalities in relation to low temperature exposure
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