Meeting Abstract
Anthropogenic climate change models predict more frequent temperature extremes and warmer winters in temperate regions such as North America. Temperate ectotherms that enter a prolonged period of dormancy (diapause) may be more vulnerable because of the direct relationship between body temperature and metabolism. The Isabella Tiger Moth (Pyrrharctia isabella) is a species that is found throughout the United States and parts of southern Canada and survives subfreezing winter temperatures in the larval stage. We tested the hypothesis that caterpillars overwintering at warmer temperatures would have higher metabolic rates and thus lower energy reserves at the end of a 4-month diapause period. Caterpillars were divided into four temperature treatment groups (2°C, 5°C, 8°C, and 11°C; n=20 in each) in lab incubation chambers while three groups (n=20 in each) were maintained outside with different amounts of straw insulation. Metabolic rate measurements were taken monthly on the animals in the lab and triglyceride and glycerol measurements were taken on all surviving individuals after the 120-day diapause period. As expected, metabolic rates increased with increasing body temperatures while triglyceride concentrations decreased with increasing overwintering temperatures. Survival was higher (range 75-90%) for the outside and the 2°C and 5°C groups while there was a sharp decline at the 8°C and 11°C treatments, 55% and 45% respectively. Glycerol, which this species uses as a cryoprotectant, was highest in the animals that overwinter outside and experienced below freezing average temperatures, while concentrations decreased with increasing temperatures in animals maintained in the lab.
