Abstract
The striped stem borer, Chilo suppressalis (Walker), overwinters as a diapausing larva. The diapausing larvae were tested for a rapid cold hardening (RCH) response and its role in the insect’s survival of sub-zero temperatures. When laboratory-reared diapausing larvae were transferred directly from the rearing temperature of 25 °C to −14 °C and maintained there for 2 h, 21% survived. Acclimation of diapausing larvae for 4 h at 5 °C before their exposure for 2 h to −14 °C increased survival to approximately 41%, indicating an RCH response. Durability of RCH effects on low temperature survival was less than 1 h. Although transient in the test, the increased survival acquired through rapid cold hardening may play a role in preparing the diapausing larvae for abrupt temperature drops in the field that would otherwise be lethal.
Highlights
Cold tolerance is important in defining an insect’s distribution and survival [1]
The present study aims to determine if rapid cold hardening (RCH) occurs in diapausing C. suppressalis larvae and contributes to survival of the larvae at sub-zero temperatures during overwintering and how long the effects of RCH on low temperature survival can last
In contrast to the results of Qiang et al [10], our results show that the protection gained through RCH was lost at a lower rate in the diapausing C. suppressalis larvae compared to non-diapausing larvae
Summary
Cold tolerance is important in defining an insect’s distribution and survival [1]. Cold tolerance can be achieved through long-term cold acclimatization, where the overwintering insects experience natural and gradual temperature changes; and through rapid cold hardening (RCH), where the overwintering insects experience a natural sudden temperature decrease for a short duration [2].In natural environments, overwintering insects may be exposed to sudden decreases in temperature in spring and autumn when seasonal adaptations are either incomplete or receding [3,4]. Cold tolerance can be achieved through long-term cold acclimatization, where the overwintering insects experience natural and gradual temperature changes; and through rapid cold hardening (RCH), where the overwintering insects experience a natural sudden temperature decrease for a short duration [2]. While seasonal acclimatization may take a long time to increase low temperature survival, RCH can enhance cold tolerance in such a short time as 30 min [5,6]. RCH has been documented across numerous insect taxa to enhance survival to acute cold stress [4,5,6,7,8,9,10,11,12,13,14], the cold tolerance gained through RCH is transient [3,8,9,10]
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