Cold hardiness and deacclimation of overwintering Papilio zelicaon pupae (original) (raw)

Seasonally-acquired cold tolerance can be reversed at warm temperatures, leaving temperate ectotherms vulnerable to cold snaps. However, deacclimation, and its underlying mechanisms, has not been well-explored in insects. Swallowtail butterflies are widely distributed but in some cases their range is limited by low temperature and their cold tolerance is seasonally acquired, implying that they experience mortality resulting from deacclimation. We investigated cold tolerance and hemolymph composition of Anise swallowtail (Papilio zelicaon) pupae during overwintering in the laboratory, and after four days exposure to warm temperatures in spring. Overwintering pupae had supercooling points around -20.5°C and survived brief exposures to -30°C, suggesting partial freeze tolerance. Overwintering pupae had hemolymph osmolality of approximately 920mOsm, imparted by high concentrations of glycerol, K(+) and Na(+). After exposure to spring warming, supercooling points increased to approximate...