Effect of heat stress on Apis mellifera intermissa and Apis mellifera sahariensis in laboratory controlled conditions: a physiological approach

Abstract

The effects of heat on honey bees have received attention in many subspecies. Nevertheless, some subspecies still remain unexplored. In this study, we investigate for the first time the effect of heat on two subspecies of honey bees endemic to Algeria, Apis mellifera intermissa which is adapted to the Mediterranean climate and Apis mellifera sahariensis, which is adapted to the hot climate of southwest Algeria. We tested the hypothesis that sahariensis is more tolerant to heat stress than intermissa. In two in-vitro tests, we reared workers of both subspecies at 4 temperatures (34 °C, 38 °C, 39 °C, and 40 °C). Then, we determined the hemolymph protein (HP) concentration, hypopharyngeal gland development (HPG), ovary development and survival. We found that the sahariensis had HPG more developed and less affected by heat than intermissa. Conversely, although intermissa had more (HP) at 34 °C, we found a significant increase in (HP) at 38 °C, 39 C° and 40 °C in intermissa than sahariensis. Although ovary development is greater in intermissa than sahariensis at 34 °C and greater at 34 °C than 38 °C, 39 °C and 40 °C, we did not record differences in ovary development between the subspecies at 38 °C, 39 °C, and 40 °C. Finally, in all conditions, sahariensis had a higher survival than intermissa.