Effects of age and Reproductive Status on Tergal Gland Secretions in Queenless Honey bee Workers, Apis mellifera scutellata and A. m. capensis

Abstract

Secretions from tergal glands are part of a queen's pheromonal control of worker reproduction in honey bees. However, in queenless honey bee colonies, workers compete to gain pheromonal, and hence reproductive dominance, over nestmates with ontogenetic changes in their glandular secretions that affect the behavioral or physiological responses of other individuals. Using gas chromatography/mass spectrometry, we investigated for the first time the age-dependent changes in tergal gland secretions of queenless workers of the clonal lineage of Apis mellifera capensis and workers of A. m. scutellata. The reproductive status of honey bee workers was determined by recording the presence of spermathecae and the level of ovarian activation. The tergal gland chemicals identified in both A. m. scutellata workers and A. m. capensis clone workers were oleic acid, n-tricosene , npentacosene, and n-heptacosene, with three additional compounds, palmitic acid, nheneicosene, and n-nonacosene, in A. m. capensis clones. We report ethyl esters as new compounds from honey bee worker tergal gland profiles; these compounds increased in amount with age. All A. m. capensis clone workers dissected had spermathecae and showed ovarian activation from day 4, while ovarian activation only started on day 7 for A. m. scutellata workers that had no spermathecae. Tergal gland secretions were present in higher quantities in bees with activated, rather than inactive ovaries. This suggests that tergal gland secretions from reproductive workers could act as releaser and primer pheromones in synergy with other glandular compounds to achieve pheromonal and reproductive dominance.

Tergal gland components of reproductively dominant honey bee workers have both primer and releaser effects on subordinate workers

“…These three esters (ethyl palmitate, ethyl oleate and ethyl stearate) have not been previously reported in tergal gland profiles of either queens or workers (Espelie et al 1990;Smith et al 1993;Wossler and Crewe 1999a) but were recently reported in tergal gland secretions of workers (Okosun et al 2015). While, the exact functions of these tergal gland components as either primer or releaser pheromones are not known in workers, the queen's tergal gland extracts elicited attraction of drones and workers, as well as suppressed ovarian activation in workers De Hazan et al 1989;Brockmann et al 2006;Wossler and Crewe 1999b, c).…”

“…m . scutellata workers (palmitic acid, oleic acid, n -heneicosene and n -tricosene) and the three ethyl esters (ethyl palmitate, ethyl oleate and ethyl stearate) (Okosun et al 2015) were tested in this study. The average concentration of tergal glands secretions of one dominant A .…”

“…Honey bee queens' pheromones serve several purposes in the colony such as regulating reproductive capacity of receivers that are normally their daughters, with a strong evidence that the degree of dominance is dependent on the queen's age, the quality and dose of her pheromones received or perceived by workers (De Hazan et al 1989;Smith et al 1993;Hoover et al 2005). Since reproductive dominance and control are achieved by pheromones, there exists strong evidence that pheromones from different glandular sources act in synergy depending on the context De Hazan et al 1989;Brockmann et al 2006;Maisonnasse et al 2010;Okosun et al 2015Okosun et al , 2017. The tergal glands, located on tergites II-IV in queens and workers (Billen et al 1986;Wossler et al 2000), are important exocrine glands that produce long-chain fatty acids, long-chain esters and a series of unsaturated and saturated hydrocarbons as components (Smith et al 1993;Wossler and Crewe 1999a;Okosun et al 2015).…”

“…Since reproductive dominance and control are achieved by pheromones, there exists strong evidence that pheromones from different glandular sources act in synergy depending on the context De Hazan et al 1989;Brockmann et al 2006;Maisonnasse et al 2010;Okosun et al 2015Okosun et al , 2017. The tergal glands, located on tergites II-IV in queens and workers (Billen et al 1986;Wossler et al 2000), are important exocrine glands that produce long-chain fatty acids, long-chain esters and a series of unsaturated and saturated hydrocarbons as components (Smith et al 1993;Wossler and Crewe 1999a;Okosun et al 2015). The secretions from the tergal gland ensure queen dominance by eliciting both primer and releaser effects in workers Vierling and Renner 1977;Wossler and Crewe 1999b, c).…”

“…Earlier on, potential tergal gland components of dominant honey bee workers that could be involved in controlling ovary activation in nest mates were identified (Okosun et al 2015). These are palmitic acid, oleic acid, n -heneicosene and n -tricosene, n -pentacosene, n -heptacosene and n -nonacosene.…”