Effects of photoperiod and temperature on endogenous ice nucleus production in larvae of the rice stem borer, Chilo suppressalis Walker (Lepidoptera: Pyralidae)

Abstract

Overwintering larvae of the rice stem borer, Chilo suppressalis Walker are known to produce endogenous ice nuclei in the muscle and epidermis as a means of avoiding intracellular freeze damage. However, the nuclei are not produced in non-diapausing larvae. To determine the effects of photoperiod and temperature on ice nucleus production, mature larvae were reared at 25°C under short and long photoperiods and acclimated to low temperatures. The ice nuclei were produced only in the muscle and epidermis of diapausing larvae reared under a short photoperiod and acclimated to low temperatures. The production of endogenous ice nuclei in the muscle and epidermis was sufficiently stimulated by short photoperiod and cold-acclimation to explain the crystallization temperature of the overwintering larvae.