A non-destructive method for longitudinal tracking of queen health: Leveraging hemolymph gene expression and gut microbiota signatures
Queen health is primary for colony success, but queen longevity has decreased drastically in recent years. Experts suggest a variety of causes including biological, environmental, chemical, and management practices. However, methods for assessing queen health in the field are presently limited to observations like queen cells, brood pattern, and egg laying rate. It has become common practice among beekeepers to simply replace all queens yearly, and data from the commercial setting suggests that young queens perform better. Here we develop and validate a longitudinal sampling protocol that combines non-destructive fecal collection with minimally invasive hemolymph withdrawal, enabling the same individual queen to be tracked across months without sacrifice. We applied the protocol to queens drawn from two source operations and assigned to five sample cohorts spanning currently-colony, currently-banked, and previously-banked physiological states across an autumn to winter transition. Sampling did not impact survival relative to unsampled controls. Fecal sequencing depth, total bacterial load, gut core taxa, and hemolymph immune transcripts provide a new perspective on queen productivity and health. Our new protocol confirmed a previously hypothesized shift in the queen gut microbiota. We discuss design and molecular refinements required to translate the protocol into a deployable tool for queen breeders and field researchers studying queen decline under field stressors.