Rapid heat hardening of honey bee queens ( Apis mellifera L.) during different developmental stages alters their morphometric characters in their adult stage

The biological effects of global warming were assessed by studying the morphological changes induced in newly hatched virgin queens exposed to rapid heat hardening during their development. Two-day-old eggs were divided into two groups. The first group was exposed to 41 °C and 70% relative humidity (RH) for 15 min. Queens raised from these preheated eggs were referred to as preheat-treated queen eggs (pH-TQ-E). The second group was left in the hive until egg hatching, and queen cups were grafted with 2-d-old larvae. Grafted cups were divided into three sets: 1) non-heat-treated maintained at 34.5 °C for 15 min at 70% RH (nH-TQ); 2) larvae exposed to 41 °C for 15 min at 70% RH just before pupation (preheat-treated queen larvae [pH-TQ-L]), and 3) the last group left to pupate, which were then exposed to 41 °C for 15 min at 70% RH just before hatching (preheat-treated queen pupae [pH-TQ-P]). From each of the treatment groups 20 queens were selected for morphological analysis and 20 for ovariole counting after mating. pH-TQ-E queens exhibited an increase in the size of seven different anatomical features compared to nH-TQ, pH-TQ-L, and pH-TQ-P queens. pH-TQ-L queens showed significantly reduced anatomical dimensions of 10 features compared to queens in the other groups. There were no significant differences in seven anatomical dimensions of queens in the four groups. Exploring the effects of rapid heat hardening on the mechanisms of temperature adaptation in honey bee queens may help us formulate a comprehensive improvement program for these insects to withstand the predicted future global warming.