Amsalem Etya, Twele Robert, Francke Wittko, Hefetz Abraham
Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
Proc Biol Sci. 2009 Apr 7;276(1660):1295-304. doi: 10.1098/rspb.2008.1688. Epub 2009 Jan 6.
Reproductive competition in social insects is generally mediated through specific fertility pheromones. By analysing Dufour's gland secretion in queens and workers of Bombus terrestris under varying social conditions, we demonstrate here that the volatile constituents of the secretion exhibit a context-dependent composition. The secretion of egg-laying queens is composed of a series of aliphatic hydrocarbons (alkanes and alkenes), while that of sterile workers contains in addition octyl esters, dominated by octyl hexadecanoate and octyl oleate. These esters disappear in workers with developed ovaries, whether queenright (QR) or queenless (QL), rendering their secretion queen-like. This constitutes an unusual case in which the sterile caste, rather than the fertile one, possesses extra components. Individually isolated (socially deprived) workers developed ovaries successfully, but failed to oviposit, and still possessed the octyl esters. Thus, whereas social interactions are not needed in order to develop ovaries, they appear essential for oviposition and compositional changes in Dufour's gland secretion (ester disappearance). The apparent link between high ester levels and an inability to lay eggs lends credence to the hypothesis that these esters signal functional sterility. We hypothesize that by producing a sterility-specific secretion, workers signal that 'I am out of the competition', and therefore are not attacked, either by the queen or by the reproductive workers. This enables proper colony function and brood care, in particular sexual brood, even under the chaotic conditions of the competition phase.
社会性昆虫中的生殖竞争通常通过特定的生育信息素来介导。通过分析不同社会条件下熊蜂工蜂和蜂后的杜氏腺分泌物，我们在此证明，该分泌物的挥发性成分呈现出依赖于环境的组成。产卵蜂后的分泌物由一系列脂肪烃（烷烃和烯烃）组成，而不育工蜂的分泌物除了含有以十六烷酸辛酯和油酸辛酯为主的辛酯外，还含有其他成分。这些酯类在卵巢发育的工蜂中消失，无论蜂群中有蜂后（QR）还是无蜂后（QL），这使得它们的分泌物类似蜂后。这构成了一个不寻常的例子，即不育等级而非可育等级拥有额外的成分。单独隔离（社会剥夺）的工蜂成功发育了卵巢，但未能产卵，且仍含有辛酯。因此，虽然卵巢发育不需要社会互动，但它们对于产卵和杜氏腺分泌物的成分变化（酯类消失）似乎至关重要。高酯水平与无法产卵之间的明显联系支持了这些酯类表明功能性不育的假说。我们假设，通过产生不育特异性分泌物，工蜂发出信号“我退出竞争”，因此不会受到蜂后或生殖工蜂的攻击。这使得即使在竞争阶段的混乱条件下，蜂群也能正常运作并照顾幼虫，尤其是有性幼虫。
