Rapid cold hardening in young hoppers of the migratory locust Locusta migratoria L. (Orthoptera : Acridiidae)

摘要

This paper describes a rapid cold hardening process for first instar hoppers of the migratory locust Locusta migratoria L. First instar hoppers of this species are often subjected to subzero temperatures or frosts in early April or May after their emergence from the soil. The mean supercooling point of hoppers is -13.0 +/- 1.4degreesC; the fact that none could survive this temperature suggests they are freezing intolerant. When young hoppers were transferred directly from 30degreesC to -7degreesC for 2h, there was only 35.8% survival. However, exposure to 0degreesC for 2h prior to transfer to -7degreesC increased the apparent survival to 75%. A similar rapid cold hardening response can also be induced by gradual cooling at rates of between 0.05 and 0.1degreesC min(-1). Rapid cold hardening also elevates the Ltime(50) Of first instar hoppers at -7degreesC by approximately 3 fold, and reduces the lethal temperature from -10degreesC to -12degreesC. However, the protection from cold shock gained through rapid cold hardening was transient and easily lost within 2h of hoppers being returned to 30degreesC. The rapid cold hardening response is possibly advantageous to first instar hoppers that are often exposed to large temperature fluctuations in Spring or early summer. [References: 36]