Involvement of the circadian system in photoperiodic regulation of insect antifreeze proteins

Abstract

AbstractSeveral species of insects produce proteins in the winter that depress the hemolymph freezing and supercooling points thereby functioning as antifreezes. These proteins produce a thermal hysteresis (difference between the freezing and melting points). This study concerns the environmental and physiological mechanisms that regulate the seasonal production of antifreeze proteins in the beetle, Dendroides canadensis. Larvae collected in early fall from a natural population and acclimated to a short photoperiod (8L/16D at 20°C, 90% RH) elevated levels of thermal hysteresis proteins (THPs), whereas those individuals maintained on a long (16L/8D) photoperiod did not. “Resonance” experiments showed that circadian rhythmicity is involved in the photoperiodic timing mechanism used by Dendroides to control antifreeze production. These results suggest that an important aspect of insect seasonality ‐ i.e., winter hardening ‐ includes complex biological timing processes of circadian nature.