Tamar Katzav-Gozansky and Abraham Hefetz. Department of Zoology, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel
Dufour’s gland (DG) secretion is idiosyncratic to the queen honeybee and constitutes a component of the multi-sourced queen signal. Queenright (QR) worker glands contain only odd n-alkanes, while queen glands also posses long-chain esters. This caste specificity is not rigid because queenless workers (QL) posses, along with developed ovaries, the queen-specific esters. There is a tight correlation between the degree of ovarian development and the amounts of esters. These esters promote worker retinue formation. The secretion produced by egg-laying workers had similar effect, albeit at a lesser degree.
The fact the pheromone plasticity in workers is regulated by the very same pheromone set when emitted by the queen is proximately and ultimately interesting. We addressed this evolutionanry conundrum by seperating the workers from the queen using single or duble mesh (SD and DM) or by replacing the queen by her pheromones in QL colonies. Workers in the DM experiment behaved as QL in having activated ovaries and expressing a queen-like secretion. This indicate that the pheromones involved are non-volatile. In the SM experiment, worker displayed a delayed ovarian development, which we attribute to interrupted transfer of the non-volatile pheromone. Substituting the queen with queen mandibular pheromone (QMP) alone or combined with Dufour’s secretion had an inhibitory effect, but it was not effective as a queen. The effect of the queen pheromones on worker pheromone expression was limited to workers with developed ovaries.
Worker-worker competition was investigated using two bees confined in an arena. In most pairs one worker had greater ovarian development. DG composition was tightly linked to ovarian development but not necessarily linked to the bee’s dominance status. We propose that the queen-like esters serve as a reliable fertility signal. Advertising ovarian status may drive less reproductively apt workers to assist their nestmates’ reproduction and thereby gain inclusive fitness.
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