Publication: A Chemical Atlas of Cuticular Hydrocarbons by Reproductive Castes in the common eastern bumble bee Bombus impatiens
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Abstract
Cuticular hydrocarbons (CHCs) serve important roles in insects as barriers against desiccation and as chemical signals within and between species. In eusocial species such as Bombus impatiens, CHCs are known to be correlated with reproductive status, behavior, and caste, but the composition of chemical profiles across different body parts and between castes remains poorly understood. This study investigates caste-specific differences in the cuticular hydrocarbon profiles of the common eastern bumble bee, Bombus impatiens, focusing on the compound classes of alkanes, alkenes, esters, ketones, aldehydes, and terpenoids. I hypothesized that queens would exhibit higher overall levels of CHCs, particularly alkanes, alkenes, and esters, and that the thorax and abdomen would show the most pronounced differences due to their association with the biosynthesis of hydrocarbons. Small colonies were established and aged under controlled conditions, after which queens and workers were dissected and separated by antennae, head, thorax, abdomen, and legs. Pentane extractions of each body part were analyzed via gas chromatography-mass spectrometry. Statistical comparisons using NMDS and ANOSIM revealed strong caste-specific differentiation across all body regions, with queens exhibiting significantly greater abundances of alkanes across all tissues and enriched levels of alkenes and esters on most body parts. The thorax displayed the greatest chemical divergence between queens and workers. The results of this experiment reinforce the idea that reproductive roles strongly shape the composition of cuticular hydrocarbons in bumble bees. Understanding these differences in chemical profiles enhances broader comprehension of eusocial organization and communication and provides further insight into potential mechanisms by which queens maintain reproductive dominance.