Rapid cold-hardening in immature stages of small hive beetle Aethina tumida Murray

The small hive beetle (SHB) Aethina tumida Murray, (Coleoptera: Nitidulidae) is a globally invasive pest of honey bees, and colonizing novel environments requires an ability to cope with local climatic conditions. Insects use rapid cold-hardening (RCH) as a quick physiological response to increase cold hardiness, and therefore, the aim of study was to determine the extent to which different life stages of SHB can undergo rapid cold-hardening, whether RCH is accompanied by the production of protective metabolites. To test for RCH, immatures stages of SHB were exposed to 12.5℃ for 5 hours and then to 0℃ for a stage-specific lethal time, and metabolic profiles of wandering larvae were studied with gas chromatography–mass spectrophotometry (GC–MS). All immature stages were capable of rapid hardening. However, rapid hardening increased survival 74% for wandering larvae, which was higher than pupae (52%) and feeding larvae (31%). Metabolomics indicated that wandering larvae exposed to RCH are metabolically distinct from untreated controls. Proline was the most highly elevated metabolite during RCH. This study shows that SHB can tolerate sudden fluctuation of cold temperatures by initiating swift physiological change.