Antennal drumming affects caste-biased gene expression during larval development in Polistes wasps

Caste differences in most social insects result from differences in environmental input, such as nutrition and exposure to pheromones. Recent evidence for Polistes wasps suggests an additional social input-- maternal vibrational signaling-- influences the probability that a larva becomes a worker or a queen as an adult. Maternal females frequently perform “antennal” drumming on the nest, and larvae subjected to this drumming develop into adults with low, worker-like fat stores. We hypothesized that maternal drumming behavior leads to worker-biased gene expression patterns in developing larvae. We paired this with a nutritional manipulation to examine the interaction between vibrational and nutritional inputs during development. To assess the effects of nutrition and drumming on caste development in Polistes fuscatus, we performed a field experiment in which nests were subjected to artificially simulated drumming and a nutritional manipulation (via foraging restrictions). Half the nests received simulated drumming at a constant, low vibrational frequency; whereas the other half received no drumming. Half of each drumming group was subjected to restricted foraging each morning (foragers could not leave the nest until mid-day) to simulate low-nutrition conditions, while the other half of the nests were not restricted, to simulate normal nutrition conditions. We predicted that larvae that experienced vibrations that simulated drumming + low-nutrition conditions would exhibit worker-like gene expression of caste biomarker genes  related to fat metabolism and heat shock, compared to those that receive no drumming and normal nutrition conditions. Our results provide the first transcript level test that maternal vibrational signals, in combination with nutritional inputs, can influence caste development via shifts in gene expression during development.