Dufour\u2019s gland analysis reveals caste and physiology specific signals in Bombus impatiens

Nathan T Derstine,Jocelyn Millar,Etya Amsalem,Abraham Hefetz,Margarita Orlova,Gabriel Villar

doi:10.1038/s41598-021-82366-2

Abstract

Reproductive division of labor in insect societies is regulated through multiple concurrent mechanisms, primarily chemical and behavioral. Here, we examined if the Dufour’s gland secretion in the primitively eusocial bumble bee Bombus impatiens signals information about caste, social condition, and reproductive status. We chemically analyzed Dufour’s gland contents across castes, age groups, social and reproductive conditions, and examined worker behavioral and antennal responses to gland extracts. We found that workers and queens each possess caste-specific compounds in their Dufour’s glands. Queens and gynes differed from workers based on the presence of diterpene compounds which were absent in workers, whereas four esters were exclusive to workers. These esters, as well as the total amounts of hydrocarbons in the gland, provided a separation between castes and also between fertile and sterile workers. Olfactometer bioassays demonstrated attraction of workers to Dufour’s gland extracts that did not represent a reproductive conflict, while electroantennogram recordings showed higher overall antennal sensitivity in queenless workers. Our results demonstrate that compounds in the Dufour’s gland act as caste- and physiology-specific signals and are used by workers to discriminate between workers of different social and reproductive status.

Highlights

Reproductive division of labor in insect societies is regulated through multiple concurrent mechanisms, primarily chemical and behavioral
To examine the role of the gland from a signal production standpoint and discover if B. impatiens females produce a social signal in the Dufour’s gland (DG) linked to their fertility status, we examined the chemical composition of the secretion as a function of caste, age, social, and reproductive status
gas chromatograph (GC)-flame-ionization detector (FID) analysis of B. impatiens DG extracts in females revealed 98 compounds comprised of aliphatic alkanes (C21-C31), alkenes, wax esters, and diterpenes (Fig. S2, Table S2)

Summary

Introduction

Reproductive division of labor in insect societies is regulated through multiple concurrent mechanisms, primarily chemical and behavioral. Reproductive division of labor in insect societies is regulated through multiple concurrent mechanisms These often involve a combination of interactions with brood[1,2], agonistic and policing behaviors among nestmates[3,4,5], and chemical signaling among individuals in the colony[6,7,8]. Negative correlation between the amount of esters a worker possesses and the aggression directed toward her during worker-worker competition over reproduction, suggesting an appeasement effect of these esters, in line with their hypothesized function as sterility s ignals[21] It is unknown if these signals are widespread in Bombus, or represents a unique chemical signaling mechanism in B. terrestris. We leverage our understanding of B. terrestris chemical ecology in order to glean new insights into potential shared or elaborated mechanisms mediating social organization across bumble bee species

Methods

Results

Conclusion